Spot-sided Coreid

Welcome to “True Bug Tuesday,” an irregularly scheduled celebration of the order Hemiptera. One of the bugs we found on our trip to south Texas earlier this month really stood out for its elegant color pattern. The Spot-sided Coreid, Hypselonotus punctiventris, was especially abundant at the Kenedy County Safety Rest Area on U.S. Highway 77, twenty miles south of Kingsville, Texas.

The rest area was landscaped with several trees and shrubs, including Yellow Trumpetbush, Tecoma stans. It was on this flowering legume that we found many specimens of the Spot-sided Coreid. It is found commonly in late October and early November in the vicinity of Austin, Texas on flowering Frostweed, Verbesina virginica.

This species apparently feeds on a variety of flowering plants as an adult. Actual known hosts upon which this insect feeds and grows include Rio Grande Abutilon (Abutilon hypoleucum), and other plants in the mallow family.

In the United States, the Spot-sided Coreid is known only from Arizona and Texas, though there is a recent record from Ashley County, Arkansas, as of April 20, 2008 (Choras III, et al., 2011). The species also occurs in Mexico, Belize, and Guatemala.

Adults average about 13 millimeters in body length, but their bold wardrobe makes them conspicuous. They can fly well, and when they open their wings they reveal a bright red patch on the dorsal (top) surface of the abdomen. Young nymphs have oversized, thickened antennae, and lack the wings adults have. I did find a final instar nymph (image below) at the Lennox Southmost Preserve, managed by The Nature Conservancy, at the very southern tip of Texas.

Despite its abundance, the Spot-sided Coreid is rarely, if ever a pest of agriculture or the garden. You are free to observe and admire this handsome insect with no fear it will doom your prize plants! Meanwhile, nearly any observations you make on H. punctiventris could represent new information on this non-pest bug.

Sources: Anonymous (“Larvalbug”). 2006. “Coreid bug (Hypselonotus punctiventris),” Hartman Prehistoric Garden.
Chordas III, S.W., R. Tumlison, H.W. Robison, and J. Kremers, 2011. “Twenty three True Bug State Records for Arkansas, With Two for Ohio, U.S.A.,” Journal of the Arkansas Academy of Science 65: 153-159.
Livermore, Laurence, Valérie Lemaître, W.R. Dolling, and M.D. Webb. 2013. Coreoidea Species File Online Version 5.0.
Valerie (aka “Larvalbug”). 2013. “Coreidae ~ Leaf-footed Bugs,” Austin Bug Collection.

"Mothapalooza" and More Upcoming Events

My posts here have been more sporadic than I would like lately, and given what is on the horizon, that is not likely to change any time soon. Here is what has been happening, and what is forthcoming:

Contract work. I have recently become contracted with Splash Media of Dallas, Texas to do work from home. This entails being part of a team that is writing blog posts for a major third party client. Assignments have been lagging lately, but that is in part because Splash has been moving their offices. I am very impressed with our team leader, and look forward to continuing my relationship with Splash Media.

Contributing to another Kaufman Field Guide. I am about halfway through my contribution to another regional field guide in the Kaufman series, this one treating the Upper Midwest (Ohio, Indiana, Illinois, Michigan, Minnesota, Wisconsin, and Iowa). If you have seen the Kaufman Field Guide to Nature of New England, then you know what to expect: comprehensive, accurate yet entertaining treatment of all things flora, fauna, and geologic.

Something really big. I am not at liberty to say much about this, but a major online enterprise recently approached me concerning a new addition to their...empire(?) Suffice it to say that if this comes to pass, it will change everything for me as far as my online presence. I hope to be able to explain this soon, but the wheels of corporate America turn slowly at times. I completed the application and testing required, and remain cautiously optimistic thanks to a friendly and supportive contact at the company.

Unidentified sphinx moth from Teller County, Colorado

"Mothapalooza." When I heard about this event, I made it known to organizer Mary Ann Barnett that I would love to attend, but didn't think I could afford it financially. Well, she promptly decided that I should be one of the "experts" in a leadership role, in exchange for registration and other expenses. How could I say "no" to that? Bonus: I get to hang out with David Wagner, author of the Princeton Field Guide to Caterpillars of Eastern North America, and Seabrooke Leckie, co-author of the Peterson Field Guide to Moths of Northeastern North America, among many other fine people. Mothapalooza is occurring at the Shawnee State Park Lodge and Conference Center, with field trips to other locations in Scioto and Adams counties, Ohio. The event runs from the evening of Friday, June 14 through the morning of Sunday, June 16. I don't think anyone is going to get much sleep....

"Bug Fest." My good friends Jeff and Sandy Belth persuaded me to present at the first inaugural "Bug Fest" at the Hilltop Garden and Nature Center on the campus of Indiana University in Bloomington on Saturday, June 22, from 10 AM to 4 PM. Thanks to Janet Creamer Martin and her husband Eric, I'll be whisked straight from Ohio's Mothapalooza to the Belth house in preparation for that event. I look forward to signing books and leading field outings there.

Bugguide.net "gathering." My great friend Margarethe Brummermann has taken it upon herself to organize the 2013 Bugguide Gathering at the Santa Rita Experimental Range research station outside of Green Valley, Arizona, Thursday, July 25 through Sunday, July 28. I encourage my readers to consider attending, as it is a very unique part of the U.S., with some amazing insects, reptiles, birds, and other creatures....including me and Margarethe!

While I am pretty much spoken for as far as events go this summer, please keep me in mind for nature festivals and other events if you need a guest speaker or field trip leader. It would be my pleasure to help introduce more people to the joys of "bugwatching" as my friend and mentor Steve Prchal calls casual entomology. Safe travels, friends.

Moth Monday: Hubbard's Silkmoth

Southern Arizona is blessed with some of the most attractive moths in the U.S. One of the more subtle beauties is a member of the giant silk moth family Saturniidae. We tend to think of the spectacular Luna Moth, Cecropia Moth, or Polyphemus Moth as popular examples of that family, but many species are much smaller. Hubbard’s Silkmoth, Syssphinx hubbardi, has a wingspan of only 56-76 millimeters, females at the higher end of the spectrum.

The overall gray color might make it seem to be rather drab, but the hind wings are bright pink, exposed when the moth is startled. The males are often attracted to lights at night, even in urban areas like Tucson.

The caterpillars are the truly colorful life stage for this species, but still amazingly cryptic. The natural host plants are Catclaw Acacia (Acacia greggii variation wrightii), Honey Mesquite (Prosopis glandulosa), and Little-leaf Palo Verde (Cercidium microphyllum). The larvae feed actively at night, and can be observed with a flashlight. Young caterpillars sit individually on the underside of leaf petioles and feed on the leaf bases. Older caterpillars cut the petiole and bend the leaves downward to access more of the foliage. Some larvae can proceed from egg to pupa in under three weeks, while others, even from the same batch of eggs, take longer.

Mature larvae are around 55 millimeters in length. They pupate underground in a cell at a shallow depth, where they spend the winter. The adult moths emerge in the early evening and begin seeking mates between 11 PM and 2 AM. There is one generation each year throughout most of its range, with the adult moths on the wing between June and September, especially in July and August. Populations in Texas may have multiple generations as evidenced by adults found at lights in November.

The geographic range of Hubbard’s Silkmoth is central Texas west through southern New Mexico and Arizona to southern California, in the mountain ranges of northeastern San Bernadino County. It also occurs in Mexico south to Veracruz, where it is even more common.

There is quite a cottage industry in rearing silk moths, and much of our knowledge of the various species comes from the community of moth enthusiasts who keep careful records and experiment with alternate host plants. Those who have kept Syssphinx hubbardi note that the caterpillars will accept Honey Locust, Black Locust, and Jerusalem Thorn as well as their native favorites.

It should be noted that many references use the genus name Sphingicampa instead of Syssphinx for this species. The adult moth imaged at the top of the page was found in Rio Rico, Arizona on July 30, 2011. The other moth and the caterpillars were found in Florida Canyon near the Santa Rita Experimental Range research station on September 3, 2011. Note that individual caterpillars are highly variable in color and pattern; and larvae of the closely-related Syssphinx Montana are nearly identical and difficult to separate from S. hubbardi in the field or by photos.

Sources: Boone, Mike, et al. 2005. Moth Photographers Group. Mississippi Entomological Museum, Mississippi State University.Oehlke, Bill. 2004. “Sphingicampa hubbardi (Dyar, 1902),” Silkmoths.bizland.com
Butterflies and Moths of North America
Powell, Jerry A. and Paul A. Opler. 2009. Moths of Western North America. Berkeley: University of California Press. 369 pp.

Spider Sunday: Prowling Spiders, Syspira

A great many spiders of other families strongly resemble wolf spiders, creating lots of confusion among those of us who are not experts. Add to that the fact that even males of web-spinning spiders wander in search of mates, sometimes blundering indoors in their quest for the opposite sex, and you can be easily perplexed. I found one non-wolf spider in Arizona that stymied me for quite some time until an expert solved the mystery.

Many wolf spiders are marked with broad, dark, parallel stripes on the carapace (top of cephalothorax), but so are grass spiders (Agelenidae), many ghost spiders (Anyphaenidae), wandering spiders (Ctenidae), and false wolf spiders (Zoropsidae). The specimen above matched none of those, and/or was not in the known geographical range for any of those families. Imagine my surprise when the verdict turned out to be the family Miturgidae, collectively known as “prowling spiders.”

The name fits the habits of these active arachnids, but I was only familiar with the longlegged sac spiders in the genus Cheiracanthium, which look nothing like the above specimen. Sure enough, it turns out the genus Syspira is common in the southwest U.S. from southern California to west Texas, and also desert areas of Mexico.

These are not terribly small spiders, either, body length varying from 10-18 millimeters, though most are on the short end of that spectrum. They have a decidedly “leggy” appearance and can span about 35 millimeters or so. Most of the ones I have seen have been prowling at night around outdoor lights, both on the ground and on walls where they grab unsuspecting moths and other insects attracted there.

There are either three or four species of Syspira currently recognized. One of them, S. pallida, might actually be a member of the genus Zorocrates, which is in an entirely different family: Zorocratidae. Yes, that is just how challenging spider taxonomy can be, even to the authorities. The general consensus is that a revision of this genus is overdue.

One study found that Syspira spiders accounted for almost half of all ground spiders in Baja California Sur, Mexico; and that they are occasionally eaten by rodents (Castañeda, et al.).

The specimens shown here are from the Tucson Mountain Park west of Tucson (Pima County), July 23, 2011; Rio Rico, Arizona (Santa Cruz County), July 25 and 30, 2011.

Note that in older references the family Miturgidae is part of the family Clubionidae. The subfamily Miturginae was given family status in 1967 by P.T. Lehtinen (Ubick, et al., 2005).

Sources: Chamberlin, Ralph V. 1924. “The Spider Fauna of the Shores and Islands of the Gulf of California,” Proc. Calif. Acad. Sci. 12(28): 561-694.Nieto-Castañeda, Irma Gisela, María Luisa Jiménez-Jiménez, and Isaías H. Salgado Ugarte. “Using Stata to anzlyze size frequency in the life cycle of a Mexican desert spider,” (alternate title: “Partitioning between syntopic congeners? A case of desert spiders”), Stata.com.
Richman, David B., David Allen Dean, Sandra Brantley, and Bruce Cutler. 2008. “The Spiders of the Arid Southwest,” New Mexico State University.
Ubick, D., P.E. Cushing, and V. Roth (eds). 2005. Spiders of North America: an identification manual. American Arachnological Society. 377 pp.

Wasp Wednesday: Not What You Think

Note: Special thanks to Bob Carlson and David Wahl for reviewing these images and confirming the identification. Ichneumon wasps are a tricky lot!

It is well known that many different kinds of insects mimic stinging wasps in order to foil their own predators. This is known as Batesian Mimicry, whereby the harmless or nearly defenseless animal achieves protection by resembling a poisonous or venomous “model” animal. There is another type of mimicry known as Müllerian Mimicry in which unrelated poisonous or venomous organisms share bold patterns, typically black and yellow, black and red, black and orange, or black and white. Tarantula hawk wasps, which deliver a very painful sting, are typically colored black or metallic blue with bright orange or red wings. In southeast Arizona, there is a large ichneumon wasp, Rhynchophion flammipennis, that also sports this wardrobe.

The wasp is a member of the subfamily Ophioninae, most if not all members of which are capable of stinging themselves, using their short, sharp ovipositors in self-defense. So, it is possible that this mimicry is Müllerian rather than Batesian. Many ichneumon wasps that do not sting still mimic the stinging spider wasps (Pompilidae), thread-waisted wasps (Sphecidae), and crabronid wasps (Crabronidae).

At least one host for Rhynchophion flammipennis is the Tobacco Hornworm, Manduca sexta. The female wasp locates the host caterpillar and injects an egg into its body. The wasp larva that emerges from the egg then feeds as an internal parasite (endoparasitoid). They are “koinobionts,” meaning that they attack very young caterpillars, and draw out their own life cycle such that the host caterpillar continues to grow and mature.

The closely-related Tomato Hornworm, Manduca quinquemaculata
The wasp larva inside waits patiently, then feeds in earnest as the caterpillar nears pupation, destroying it before it actually does pupate. The wasp larva then spins a dense silken cocoon in which it pupates. Since sphinx moth caterpillars pupate underground, the wasp cocoon is likewise located in the pupal chamber in the soil.

This species is known to occur in Arizona, Mexico, Nicaragua, and Ecuador. It is a member of the tribe Enicospilini, most of which are tropical wasps. There are only two other known species in the genus. While most Ophioninae are nocturnal, Rhynchophion are day-active. They even visit flowers for nectar.

Curiously, I have found other images of this species online, but in every case the antennae are black. Perhaps antenna color varies with gender? Certainly much remains to be learned about this spectacular wasp, including whether it has other hosts. Anyone who rears sphinx moths from Arizona, Mexico, or Central America should make note of any parasitic Hymenoptera that emerge from their livestock.

The specimen imaged here was observed at the mouth of Madera Canyon in Pima County, Arizona on August 21, 2011. It hung motionless from the Desert Broom plant it was clinging to. Perhaps it collided with a vehicle entering the canyon and was recuperating.

Sources: Carlson, Robert W. 2009. “Family Ichneumonidae,” Database of Hymenoptera in America north of Mexico. Discover Life.
Gauld, Ian D. and David B. Wahl. 2013. “Subfamily Ophioninae,” Genera Ichneumonorum Nearcticae. The American Entomological Institute.
Kester, K. and J. Tuttle. 1999. “Host identified for Rhynchophion flammipennis (Hymenoptera: Ichneumonidae). Southwest. Nat. 44(1): 87-88.

Moth Monday: Palo Verde Webworm

Palo Verde trees are a fixture of the Sonoran Desert landscape in southern Arizona, so it comes as something of a surprise that so little is known about one of the most obvious insects that lives on that plant. The Palo Verde Webworm, Faculta inaequalis, remains rather mysterious despite its abundance.

This insect is a member of the family Gelechiidae (twirler moths), all of which are quite small. The adult moth varies from about 5-7 millimeters in length. Mature caterpillars are at most 12.5 millimeters.

It is the activities of the larvae that are most conspicuous. Amazingly, I can find no images of the immature stages other than these that I took myself on May 25, 2010 in Greasewood Park on the western edge of Tucson, Arizona. The caterpillars spin silken tubes along the lengths of twigs on the host tree. These silk sleeves they decorate with their droppings (frass), perhaps to increase the degree of shade they can enjoy during the heat of the day. The tubes appear to be connected to each other by a random network of additional silk threads, the “webbing” that gives these insects their common name.

The larva ventures out during cooler hours to nibble on leaves or even the bark. Palo Verde trees photosynthesize both with their leaves and their limbs; and they don’t hesitate to shed their leaves during periods of draught. Damage done by caterpillars is therefore negligible, and Faculta inaequalis seldom, if ever, becomes more than a nuisance or cosmetic pest.

The adult moths are not at all uncommon at lights at night, even in urban areas where the host trees are often planted as ornamentals. The Foothills Palo Verde, Parkinsonia microphylla, is the preferred host of this moth, and the tree is common in upland areas of the Sonoran Desert in coarse soils. Whitethorn Acacia (Acacia constricta) is an alternate, occasional host.

Part of the problem in finding out more about this peculiar lepidopteran is that it has previously been known by different scientific names, including Gelechia inaeaqualis and G. clistrodoma. Werner and Olson summarized the biology of the species in their book Insects of the Southwest, under the name Bryotropha inaequalis. Online references frequently do not use any scientific name.

The range of the Palo Verde Webworm is apparently restricted to southern California, Arizona, southern New Mexico, and Baja California Sur. Adult moths have been taken from January to April, and also August, so there are probably several generations per year.

Sources: Powell, Jerry A. and Paul A. Opler. 2009. Moths of Western North America. Berkeley: University of California Press. 369 pp.
Werner, Floyd and Carl Olson. 1994. Insects of the Southwest. Tucson, AZ: Fisher Books. 162 pp.

Spider Sunday: Homalonychus

The spider family Homalonychidae is so obscure that there is not even a common (English) name for them. I would never know they even existed had it not been for finding a few specimens under old railroad ties in Tucson Mountain Park, Arizona, on April 23, 2011. I was confounded as to their identity, and I honestly don’t recall how I came to conclude what they were.

Female in potential defensive posture

Perhaps they should be called “encrusted spiders,” because that is the appearance they usually give in the field. Indeed, particles of sand, soil, and fine debris catch in the short, stiff setae (hairs) that cover the carapace, abdomen, and legs of these spiders. They do not, however, bury themselves in loose sand like some members of the family Sicariidae.

Mature specimens are fairly large, females measuring 8.5-10 millimeters in body length, males 6.5-7 millimeters. Their characteristic sprawling posture at rest makes them appear larger still.

Male

The family contains only one genus, Homalonychus, with only two species: H. theologus and H. selenopoides. The collective range of those species is small, from southern California and Nevada to Arizona, the Baja California peninsula, and northwest Mexico. The species illustrated here is probably S. selenopoides, judging by differences found in molecular DNA studies of the two species (Crews & Hedin, 2006). An additional species was thought to occur in India, but that one has now been placed in the genus Storenomorpha, family Zodariidae.

While homalonychids possess three pairs of spinnerets, they do not spin webs, and apparently do not lay down draglines in the course of moving about their environs. Males do employ silk to loosely bind the legs of females during mating (Alvarado-Castro & Jiménez, 2011). Mated females make silken egg sacs that they cover with small pebbles and other particles.

Female with egg sac

Whether these spiders are generalist predators or specialists is unknown. They have been observed in the field feeding on insects related to silverfish (order Zygentoma), and cannibalizing their own kind. Specimens in the laboratory feed readily on pomace flies (Drosophila) and crickets. Additionally, it is suspected that these are long-lived spiders that probably survive at least two years in the wild.

Homalonychids can be quite common, but I suspect they don’t disperse very far as juveniles and probably exist in scattered, localized populations. I welcome hearing what other people have experienced and observed regarding this strange family of spiders. The placement of this family in the larger context of phylogenetic relationships remains largely mysterious, given their relatively advanced physical features, but mostly primitive behavior.

Sources: Alvarado-Castro, José Andrés and María Luisa Jiménez. 2011. “Reproductive behavior of Homalonychus selenopoides (Araneae: Homalonychidae),” J. Arachnol. 39(1): 118-127.
Crews, Sarah C. 2005. Homalonychidae. P. 118 in D. Ubick, P. Paquin, P.E. Cushing, and V. Roth (eds.) Spiders of North America: an identification manual. American Arachnological Society.
Crews, Sarah C. and Marshal Hedin. 2006. “Studies of morphological and molecular phylogenetic divergence in spiders (Araneae: Homalonychus) from the American southwest, including divergence along the Baja California Peninsula,” Mol. Phylogenet. Evol. 38: 470-487.
Vetter, Richard S. and James C. Cokendolpher. 2000. “Homalonychus theologus (Araneae, Homalonychidae): description of eggsacs and a possible defensive posture,” J. Arachnol. 28: 361-363.

Wasp Wednesday: Stizoides renicinctus

NOTE: I failed to make it clear how many wasps, and even some flies, look nearly identical to this species if you are not an entomologist. There is the Blue-winged Wasp, Scolia dubia, spider wasps (Anoplius atrox and others), and even the enormous fly Mydas clavatus that are equal to or larger than Stizoides renicinctus. Stizoides renicinctus is also not nearly as common as these other wasps. So, those of you insisting you are seeing this species have likely mistaken it for something else. Thank you, and my apologies.

One of the cool “surprise bugs” from the ”wasp tree” was a kleptoparasitic wasp (I’ll explain that term below), Stizoides renicinctus. This insect is so obscure that it has no common name in English, but that doesn’t take anything away from its unique life history.

S. renicinctus is one of only two species in the genus occurring in North America. Globally, there are thirty species in the genus, most found in Africa, Mediterranean Europe, the Middle East, and India. The only other species in the U.S. is S. foxi, restricted to Arizona (and south into Mexico).

Field marks that help to identify S. renicinctus include an all black body with a red or orange band on the second dorsal abdominal segment (tergite), dark wings with translucent wingtips, and an overall elongate appearance. Both genders are nearly identical in appearance and size, at about 16-18 millimeters.

One usually encounters the males taking nectar from flowers. I was surprised at the fair number of them on the saltcedar tree during the latter half of June here in my Colorado Springs neighborhood. I have also seen this species in southern Arizona, coming to the blossoms of Seepwillow, Baccharis salicifolia in dry arroyos or along rivers.

Females are mostly busy seeking hosts for their offspring. The term “kleptoparasite” refers to an animal that essentially raids the refrigerator of its host organism. That means the parasite feeds on the material stored as food by its host. S. renicinctus is known to exploit the food caches of other solitary wasps in the genera Prionyx and Palmodes. Female Prionyx hunt grasshoppers (Acrididae), while Palmodes hunts katydids (Tettigoniidae). The wasps dig burrows and stock at least one prey item per cell that a single larva will consume to grow and mature into an adult wasp of the next generation. The female Stizoides renicinctus locates the closed burrow of a host, digs it open, destroys the host egg, and replaces it with one of her own. The larva that hatches will eat the food the host mother wasp took such care in providing.

It has been noted that S. renicinctus is not always solitary. Individuals will gather in “sleeping” clusters on vegetation at night. They apparently do this in the face of impending inclement weather, too. I found a loose aggregation forming in the saltcedar bush on the afternoon of June 16 as storm clouds began to gather. These wasps will sometimes be found amid sleeping clusters of other solitary wasps as well.

These wasps are quite efficient parasites, as documented by I. LaRivers in a 1945 paper in American Midland Naturalist. He found the species parasitizing Palmodes laeviventris in Elko County, Nevada. The Palmodes were doing local agriculture a service by slaying Mormon crickets (a type of wingless katydid), but the Stizoides wasps were also reaping the benefits. LaRivers estimated a parasitism rate of about 7.5 percent, which he extrapolated to roughly 10,000 destroyed Palmodes nests in about 350 square yards.

Ok, so Stizoides is an outlaw of the Old West (it actually ranges from Michigan and Wisconsin south to North Carolina and west to Alberta, British Columbia, California, Arizona, and Mexico). I would like to think that seeing a good number of specimens means that there is also a thriving population of host wasps. That in turn means abundant grasshopper prey, and thus a healthy habitat.

Be on the lookout for Stizoides where you live, and see if you can find one in the act of finding a host. You may discover a relationship previously unknown to science. You just never know.

Sources: Bohart, R.M. and A.S. Menke. 1976. Sphecid Wasps of the World: A Generic Revision. Berkeley: University of California Press. 695 pp.
Evans, Howard E. and Kevin M. O’Neill. 2007. The Sand Wasps: Natural History and Behavior. Cambridge, Massachusetts: Harvard University Press. 360 pp.

Wasp Wednesday: Triscolia ardens

Have you ever been involved in a hit-and-run accident? If so, then you know what it feels like to be a scarab beetle grub being attacked by a scoliid wasp. The only difference is that the insect encounter is no accident. Female scoliid wasps actively seek out the beetle grubs as hosts for their larval offspring. Here in southern Arizona, one of the largest and most conspicuous of the scoliids is Triscolia ardens.

T. ardens is the only member of its genus in North America north of Mexico. It occurs from Texas to southern California and is relatively common. Females are robust, with short antennae. Males have long antennae and sport a three-pronged "pseudosting" at the tip of the abdomen. The remainder of this post will treat scoliids in general because so little is known about the biology of individual species.

Scoliids of both genders can be found visiting flowers, especially milkweed, seep willow (Baccharis), saltcedar (Tamarix), desert willow (Chilopsis), mesquite (Prosopis), scalebroom (Lepidospartum), and buckwheat (Eriogonum). At the end of the day, the wasps bed down singly on vegetation, remaining alert but not not terribly motivated to move as the desert temperatures begin to fall.

Their life cycle can be generalized as follows. The female wasps fly low over the ground, somehow divining the presence of subterranean scarab beetle grubs. Once one is detected, the wasp digs it up, using her densely spiny legs to send the soil flying. Once she unearths the grub, she stings it into paralysis. This allows her to lay a single egg on the grub. After she accomplishes her mission, she re-buries the grub and flees the scene of the crime (some species have been observed moving the grub deeper into the soil and fashioning an earthen cell around it before depositing an egg and sealing the tunnel). The beetle grub apparently never recovers from its coma. The egg of the wasp hatches, and the larva that emerges will feed as an external parasite on its host for about a week or two before spinning a silken cocoon and pupating. Most North American scoliids overwinter in the pupal stage.

The size of the mature wasp is dependent on the size of the host beetle grub. Even the largest Triscolia ardens seldom exceed about 30 millimeters in body length, but one frequently finds “dwarfs” that obviously suffered a lack of nutrition in their youth. Tropical scoliids, however, are among the largest (certainly heaviest) wasps in the world, exceeding 50 millimeters in body length.

Other online resources include this PDF on scoliid wasps of Florida. It is an excellent introduction to the family as a whole, treating Florida scoliids in particular. Another PDF on Scoliidae of California addresses some southwestern species but it appears incomplete.

Clearly, much remains to be learned about these highly attractive and obvious wasps. Any documentation with video is likely to be a first, or nearly so; and host associations are almost entirely lacking for our native scoliids (some species have been introduced to the U.S. to control exotic scarab pests).

Wasp Wednesday: Polistes arizonensis

Here in southern Arizona there are several species of paper wasps in the genus Polistes. What intrigues me is that you seldom find more than one species in any particular location. At the least, one species is usually dominant and other species scarce. Here in the city of Tucson, one of the more abundant urban species is P. arizonensis.

At first glance, this species could be mistaken for Polistes exclamans, a species common in the eastern and southern U.S. Indeed, P. arizonensis was once considered a subspecies of P. exclamans. The Arizona wasp only ranges from Arizona to southern California and Mexico.

One of the favorite places for P. arizonensis to nest is under collapsed palm fronds. Several large colonies can coexist in close proximity under these weathered but sturdy leaves. Here is an example I found at the Sweetwater Wetlands in northwest Tucson.

I have found several female (worker) wasps overwintering on such insulated nests, so the large combs may represent the expansions of the previous year’s occupants. Well, that was my theory until I took some of these old nests as souvenirs and found they harbored huge numbers of dermestid beetle larvae that eventually became adult beetles flying freely around my apartment. The invasion of scavengers like dermestids suggests that the combs held deceased wasps (probably in the pupal stage), and those cells are not likely to be re-used.

Interestingly, Polistes arizonensis seems just as comfortable nesting amid tangled shrubbery, which leaves them perhaps more exposed to the elements, and their prime enemies: ants. The wasps do have an answer for the ants, though. The female wasps secrete a substance that repels ants, and apply this blackish goo liberally to the paper pedicel that attaches the nest to the substrate (stem, frond, ceiling, whatever). The repellant is produced by sternal glands located internally on the underside of the abdomen. The secretion consists of long-chain carboxylic acids. One study showed that the unsaturated acids (palmitoleic, linoleic, and oleic) in the secretion were effective in repelling at least three species of ants, for up to four days (Dani, et al., 1996).

Like most paper wasps, P. arizonensis seems to prefer hunting caterpillars as food for the larvae back at the nest. Notice the worker chewing up a caterpillar in the image below, prior to feeding the morsel to a larva in one of the cells in the nest.

This nest was located under the sheltering roof of a “ramada” overlooking one of the ponds at Sweetwater Wetlands.

You can tell the gender of many kinds of paper wasps by looking them in the face. Females usually have dark, triangular faces, whereas males have square, yellow faces. Such is the case with P. arizonensis. Also note the hooked tips on the antennae, and blunt tip of the abdomen in the male specimen imaged below.

I find that this species is remarkably tolerant of close approaches to its nests. I was able to get these images without the occupants even taking an alarm stance. When paper wasps stand on tip-toe (tip-tarsi?), with wings raised and splayed, it means “You have come too close! Back off now or suffer the consequences.” By retreating even a short distance after such a warning you prevent an attack and the wasps go back to business as usual. Understand that I am not recommending you trespass active colonies, but do use your own judgment and enjoy observing their interactions.

Sources: Dani, F. R., S. Cannoni, S. Turillazzi, and E. D. Morgan. 1996. “Ant repellent effect of the sterna gland secretion of Polistes dominulus (Christ) and P. sulcifer (Zimmermann). (Hymenoptera: Vespidae),” Jour. Chem. Ecol. 22: 37-48.

Spider Sunday: Arizona Blonde Tarantula

Without a doubt, one of the iconic animals of the Sonoran Desert is the tarantula. What would a Western, or desert horror movie be without a shot of one of these giant spiders moving leisurely across the landscape? Maybe a tumbleweed, too, though a Russian Thistle moves faster than a strolling tarantula.

Tarantulas belong to the family Theraphosidae, and only the genus Aphonopelma is native to North America. There are 54 currently recognized species north of Mexico, and determination to species level is complicated by the fact that these are primitive animals in the evolutionary sense, with simple genitalia that don’t allow for easy comparison. That said, the most common species here in southern Arizona is the “Arizona Blonde,” Aphonopelma chalcodes.

It is mature male spiders that are most often seen crossing roads, especially at night, during the summer monsoon season. The male is easily recognized by his relatively lanky appearance, with a smaller abdomen and longer legs than the female. His front legs also have a spur on the underside of the tibial segment. The spurs are used to hold the female’s fangs at bay during mating. His coloration also differs from that of the female. His legs are entirely black, while the female has black femur segments with the remaining leg segments brown.

Both sexes live in burrows in the ground. Females rarely venture out, lest they become even more vulnerable to tarantula hawk wasps, and other predators such as coatimundi. An occupied burrow will have a thin curtain of silk over the entrance during the daytime. The spider will sit at the lip of its tunnel during the night, the better to ambush any unsuspecting insect or other small animal that comes within striking range. During the winter months the spiders plug their burrows with soil. Fat reserves sustain the spider during those lean months.

Tarantulas begin life as surprisingly small spiders, like the one below. Margarethe Brummermann found this specimen under a cow patty near Sunsites in the Dragoon Mountains. It takes a minimum of seven years for a tarantula to reach sexual maturity, and that is for captive specimens that receive regular meals and are otherwise provided with optimal conditions.

The black patch on the abdomen of the spiderling indicates special hairs that tarantulas use in self-defense. Rather than striking at an adversary with their fangs, our North American species literally kick themselves in the rear. Be careful if you see a tarantula doing this. It is dislodging short, microscopically barbed hairs that easily become airborne. These hairs, if they contact mucous membranes of the nose or eyes, cause extreme irritation. Some people may also have an allergic reaction, including a rash or other inflammation of the skin. Even a molt (shed “skin”) of a tarantula can bring about an allergic reaction in those people who are susceptible.

Tarantulas are among the very few spiders that continue molting after they reach adulthood. This process helps replenish those defensive hairs, and shed mites, other parasites, and dirt. Captive female spiders like the one shown above have been known to live as long as thirty years, but “wild” specimens likely don’t survive nearly as long. Males, after reaching adulthood, abandon their burrows in search of mates. After successfully breeding they usually die.

Members of the genus Aphonopelma are collectively distributed west of the Mississippi River and as far north as Missouri, Colorado, Utah, Nevada, and the southern two-thirds of California.

Life Cycle of a Leaf Beetle

Leaf beetles of the family Chrysomelidae seem to be particularly diverse here in southern Arizona. One of the most common species is Leptinotarsa lineolata, a relative of the familiar Colorado Potato Beetle. A visit to one arm of the Sonoita Creek State Natural Area in Rio Rico, Arizona on July 31 found this beetle in profusion, and all life stages but the pupa present.

The adult beetles are about 7-8 millimeters long, but colorful. The head and thorax are metallic green, while the elytra (wing covers) are ivory with black streaks. The beetles and their larvae feed exclusively on Burrobrush (Hymenoclea monogyra). The beetles become numerous after the onset of monsoon rains, usually in early or mid-July. They quickly set about reproducing.

Once mated, the female beetles lay eggs in rows along the edge of a leaf near its tip. The large numbers of eggs and their bright yellow color make them very conspicuous.

Larvae hatch from the eggs in about seven days and commence feeding on the burrobrush leaves. The grubs go through four instars (intervals between molts) before pupating. I assume the large larvae I imaged are fourth instar. The larvae probably sequester the toxins in the plant to use in their own chemical self-defense. That would explain the bright black, white and yellow markings reminiscent of Monarch butterfly caterpillars. Such toxic insects tend to advertise their unpalatable nature through “warning colors,” a phenomenon known as aposematism.

Well, no wonder I couldn’t find the pupal stage. An unpublished study by Ross Arnett and Richard L. Jacques in 1971 followed L. lineolata through its entire life cycle, and they found that pupation occurs in the soil. Adult beetles emerged from the pupae roughly ten days later.

According to Michael Plagens’ account of this species, the beetles are capitalizing on disturbed riparian zone habitats where their host plant thrives in the wake of cattle grazing. Burrobrush is toxic to mammals, so livestock leaves it alone while eating competing vegetation.

Leptinotarsa lineolata ranges from Texas to California, and south into Mexico. There is no missing this insect if you are at all observant and in the right habitat at the right time. Check them out!

Source: Jacques, Richard L., Jr. 1988. The Potato Beetles: the Genus Leptinotarsa in North America (Flora & Fauna Handbook No. 3. Gainesville, Florida: Flora & Fauna Publications. 147 pp.

Wasp Wednesday: Steniolia eremica

The sand wasps are among my favorite insects. They are incredibly industrious, colorful, and kill pesky insects like flies for a living. Members of the genus Steniolia are particularly ornate and I recently encountered a species new to me. I was hiking in Florida Canyon (pronounced Floor-EE-duh) in the Santa Rita Mountains of southern Arizona with Margarethe Brummermann on April 21 when we came upon some blooming thistles (Cirsium sp.). Several insects were visiting the blossoms, including males of Steniolia eremica.

Ordinarily, these insects are highly vigilant and easily startled into flight. Spellbound by the nectar-laden thistles, these dudes were easily approached. Male sand wasps are larger than the females, and these were substantial insects by sand wasp standards, maybe 22 millimeters in length, or more.

This species was described fairly recently, in 1964, by James E. Gillaspy, the leading authority on the genus. He considered S. eremica to be less abundant than other species that share its range, from central Nevada south through Arizona, southeast California, and into Mexico. The adult wasps have been collected on the wing from March to August.

Not much is known about the biology of this species, though one female specimen in a collection is pinned with a robber fly (family Asilidae). The assumption is that the fly was prey of the wasp, but considering how powerful asilids can be, I wonder if the reverse was not the case. Female Steniolia in general hunt flies, paralyzing them with a sting, and then take them back to a burrow where the wasp’s larval offspring await their next meal.

Besides my own personal observation of the males on thistle flowers, other nectar sources for the wasps include Palafoxia (Spanish Needles), Petalonyx (sandpaper plant), Melilotus (sweetclover), and Chilopsis (desert-willow). Steniolia have extra-long “tongues” to probe for nectar. The galea and glossa in particular are elongated and not retractable. These straw-like segments are tucked between the legs of the wasp when not in use.

Earlier in the “Wasp Wednesday” series I wrote about another species, Steniolia elegans. The basic biology is the same among all fifteen species. More information can be had in the form of revisions of the genus and documentation of California species.

Sources: Bohart, R. M. and James E. Gillaspy. 1985. “California Sand Wasps of the Subtribe Stictiellina,” Bulletin of the California Insect Survey volume 27. Berkeley: University of California Press. 89 pp.
Gillaspy, James E. 1964. “A Revisionary Study of the Genus Steniolia.” Transactions of the American Entomological Society. LXXXIX: 1-117.

Spring (Butterfly) Beauties

Spring has definitely “sprung” here at the Tucson Botanical Gardens. Many flowers are in bloom, and native butterflies are taking full advantage of the bounty of nectar. We are now up to forty (yes, 40) confirmed butterfly species seen on the grounds. Recent observations have yielded some surprises, including one supposedly rare species of skipper.

The “usual suspects” are here: Pipevine Swallowtail, Giant Swallowtail, Checkered White, Southern Dogface, Sleepy Orange, Dainty Sulphur, Gray Hairstreak (image above), Marine
Blue, Reakirt’s Blue, Fatal Metalmark, Gulf Fritillary, Texan Crescent, American Snout, and Painted Lady. What is new, then? Plenty.

One of the more startling species I spotted a couple weeks ago was a Desert Orangetip, Anthocharis cethura. Just as I focused my camera on it, away it flew. That figures. I haven’t seen one since, either.

Another mild surprise was a Mourning Cloak, Nymphalis antiopa (image below). This large, black butterfly with a creamy border is more typical of riparian areas since it feeds on willow in the caterpillar stage. This male specimen was frequenting the bird garden. He perched where he had a good vantage point and darted out after any intruder, especially other butterflies like Pipevine Swallowtails. After a brief chase he returned to the same area he started from. He even alighted on a visitor’s ballcap while I was watching.

The real shockers have come from the skippers in the family Hesperiidae. Sure, the Fiery Skipper, Orange Skipperling, Common Checkered-Skipper, and Eufala Skipper are common enough, but I’ve seen other species that I would not expect here. The first of these was a Sleepy Duskywing, Erynnis brizo, seen on March 4 (image below). This species feeds on oak as a caterpillar, so it really belongs a couple of thousand feet higher in elevation. There it was, though, on a Dalea blossom in the butterfly garden.

The Funereal Duskywing, Erynnis funeralis, is a much more likely species here at the Gardens. I finally spotted one on March 19, but failed to get a picture. This fast-flying skipper is fairly large. Mostly black, it has a blazing white border along the edge of its hind wing which makes it easily identifiable.

Another surprise was an Arizona Powdered-Skipper, Systasea zampa (image above), sitting on a brick in the barrio garden late in the afternoon of March 6. I initially figured it for a Fatal Metalmark, to which it bears superficial resemblance.

The Golden-headed Scallopwing, Staphylus ceos, also resembles a metalmark at first glance.

The most amazing of all the spring skippers was a Violet-clouded Skipper, Lerodea arabus. It is relatively non-descript (see image below), save for a distinct dark brown patch on the underside of its hind wing. Certainly no violet to be seen! You would think that this would be among the more abundant of butterfly species given that the caterpillar feeds on Bermuda grass, barnyard grass, and other weedy plants. Instead, most reference books list it as “rare.”

Last but not least, I added a species by proxy. One of the visitors to the Butterfly Magic greenhouse, Carolyn Vieira, mentioned to me that she also takes pictures of butterflies on the TBG grounds. I told her I had yet to see a Great Purple Hairstreak, Atlides halesus, and as luck would have it she had a picture she took a couple years ago or so. I still expect to see this spectacular butterfly here myself, but it is nice to have an existing record.

The diversity of wildlife to be found at the Tucson Botanical Gardens continues to astound me. Just in cursory observation I’m closing in on 200 species of animals, from arthropods to apes (we Homo sapiens). The wide variety of plants, and the constant watering no doubt provides a literal oasis for all.