Thursday, March 21, 2013

OrThoptera Thursday: Northern Green-striped Grasshopper

No sooner has the grass sprung up in the early spring than there are insects out to eat it. Walk through an open field or meadow and you may be surprised to find that you are startling grasshoppers into flight already. At least they will be hopping. Several species of grasshoppers (family Acrididae) overwinter as older nymphs and mature quickly once temperatures warm consistently and the days lengthen. One of those early season species is Chortophaga viridifasciata, the Northern Green-striped Grasshopper.

Adult female, Colorado Springs

Last year in Colorado Springs I found nymphs of this species along an urban trail on March 10; and adults in an open field on March 27. This year, which has seen a rollercoaster of temperature extremes, I suspect they will mature later.

Nymph, Colorado Springs

Chortophaga viridifasciata is rather variable in color and pattern, which makes it difficult for the average person to identify. Its early appearance is one clue. A distinguishing physical feature is the pronotal ridge, which is strong, straight, and broken by only a single sulcus midway along its length. The pronotum is the top surface of the thorax, and the ridge runs right down the middle, lengthwise. In profile, the ridge is evenly straight. It is at least somewhat arched in early season Arphia species.

Females of the Northern Green-striped Grasshopper are larger (28-38 millimeters) and heavier-bodied than males, and are usually green with brown markings. Males (23-30 millimeters) are mostly brown with few if any green markings. Below is an image that shows males from the same population can still be brown or green.

When the grasshopper flies, the hind wings are exposed. They are pale yellow in color at their base, with the outer half smoky brown to nearly black. This also contrasts with similar Arphia species that have the hind wings bright yellow, orange, pink, or red. Flight covers a short distance, but may be noisy. Male band-winged grasshoppers in general (subfamily Oedipodinae) are capable of making “crepitation flights” whereby the front and hind wings snap together rapidly to make a crackling noise. This is accomplished at the grasshopper’s will, so other flights can be silent. Crepitation flights are often associated with courtship displays, but not always, and females of some species can crepitate as well.

Male from South Carolina

C. viridifasciata is an abundant grasshopper found east of the Rocky Mountains from southern Canada to northern Central America. It also creeps into Arizona and Idaho, with scattered records in extreme southeast British Columbia. The preferred habitat is wet areas with short grass. While there is only one generation in most of its range, there can be two generations in southern areas, where the adults can overwinter.

Southern populations have been considered a separate species, C. australior, but there is reason to suspect this is an artificial distinction. The “two” certainly overlap as far north as the Ohio River Valley and Nebraska. Where there are two generations of C. viridifasciata, the later generation tends to resemble C. australior. Many authorities still separate the two, with C. australior confined in its range to the southeast from Georgia to Florida and west to east Texas.

The only other species in this genus are C. Mendocino, found in Mendocino County, California; and C. cubensis found in Cuba.

Male from western Massachusetts

Be on the lookout for this grasshopper where you live. Even in New England they are likely to be out by the end of May at the latest, and March or April in most other locations.

Sources: Capinera, John C., Ralph D. Scott, and Thomas J. Walker. 2004. Field Guide to the Grasshoppers, Katydids, and Crickets of the United States. Ithaca, NY: Comstock Publishing Associates (Cornell University Press). 249 pp.

DiTerlizzi, Tony and Dave Ferguson. 2012. “Genus Chortophaga,”

Tuesday, March 19, 2013

True Bug Tuesday: Exporting the Western Conifer Seed Bug

We spend a great deal of time and energy in the U.S. wringing our hands over invasive species from Europe and Asia, but we forget we sometimes export our own pests in return. Last week, a thread emerged on the Entomo-l listserv from a doctoral student in France who inquired about how to control the Western Conifer Seed Bug, Leptoglossus occidentalis. Seems it was first detected in Europe in northern Italy in 1999, but has since spread through most of the continent. It was first found in the United Kingdom at Weymouth College in Dorset in January, 2007.

This rapid colonization should come as no surprise. Here in its native North America, the WCSB has shown the same propensity for expanding its range. Once confined to the western U.S., it began creeping eastward in the 1950s. By the 1990s it had reached the east coast.

Leptoglossus occidentalis is generally considered at most a nuisance pest that likes to spend the winter inside homes where it emerges at inopportune times, flies with a loud droning noise, and produces a disagreeable (to some people at least) odor when accosted.

The conversation on Entomo-l revealed that the bug is not always so innocuous. It has beak-like mouthparts and it can pierce polyethylene (PEX) tubing used in plumbing and radiant heating. The bugs secrete a protein in their saliva that forms a protective sheath around their mouthparts while they feed, and this sheath is left behind as evidence. Hence, investigators were able to sleuth the culprit in the case of the “weeping” pipes that lose water through the pinhole punctures caused by bugs exploring novel surroundings (Bates, 2005).

Obviously, a much more pressing concern for our friends abroad is the prospect of WCSB becoming a forest pest. They feed on seeds inside the cones of conifers, especially pines but also Douglas Fir and Eastern (Canadian) Hemlock. They rarely cause significant damage in natural stands, but are a potential problem in conifer seed orchards.

Indeed, laboratory studies show that late-season feeding in particular can have adverse effects, reducing the storage reserves of lipids and buffer-insoluble (crystalloid) proteins by up to 78% and 97% respectively in seeds of Douglas Fir (Bates, et al., 2001). WCSB certainly impacts second-year cones in orchards. Seed production can be reduced by 75% in Lodgepole Pine under some circumstances (Bates, et al., 2002).

Our collective desire for “free” trade and global commerce guarantees that we will continue to exchange fauna and flora that could become problematic outside their native regions. Are we properly informed of the risks? One is left to wonder about the consequences.

Sources: Bates, Sarah L., Cameron G. Lait, John H. Borden, and Allison R. Kermode. 2001. “Effect of feeding by the western conifer seed bug, Leptoglossus occidentalis, on the major storage reserves of developing seeds and on seedling vigor of Douglas-fir,” Tree Physiol. 21: 481-487.
Bates, Sarah L., Ward B. Strong, and John H. Borden. 2002. “Abortion and Seed Set in Lodgepole and Western White Pine Conelets Following Feeding by Leptoglossus occidentalis (Heteroptera: Coreidae),” Environ. Entomol. 31(6): 1023-1029.
Bates, S.L. 2005. “Damage to common plumbing materials caused by overwintering Leptoglossus occidentalis (Hemiptera: Coreidae),” Can. Entomol. 137: 492-496.
Taylor, Steven J., Gluseppi Tescari, and Mauro Villa. 2001. “A Nearctic Pest of Pinaceae Accidentally Introduced Into Europe: Leptoglossus occidentalis (Heteroptera: Coreidae) in Northern Italy,” Ent. News 112(2): 101-103.

Monday, March 18, 2013

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),”
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.

Sunday, March 17, 2013

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”),
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.

Friday, March 15, 2013

Fly Day Friday: Comantella robber flies

Here along the Front Range in eastern Colorado, among the first flies of spring are unique little robber flies in the genus Comantella. When I first saw one I thought it looked like a march fly (Bibionidae), but behaved like an asilid.

Comantella are also among the last flies seen in the fall, as demonstrated by the above image taken on Novermber 29, 2011 in Colorado Springs. This unusual seasonal appearance of the adults (early and late), plus the presence of a slender spur on the tip of the front tibia (“shin” segment), helps to separate this genus from similar genera in the Asilidae. They are decidedly humpbacked when viewed in profile. Little appears to be known concerning their biology, though it is suspected that the adult flies overwinter in protected places. One specimen of the species C. fallei was observed preying on a small wolf spider in the genus Pardosa (Dennis, et al., 2012).

The taxonomy of Comantella is not very straightforward, either. At least one expert on asilids believes the genus is in bad need of revision. Current keys to species seem to revolve around the length of the terminal style as compared to the third antennal segment, and coloration of the hairs on the body.

These are small or medium-sized flies, 10-15 mm in length, and covered in long hair, even on their legs. The top of the thorax features a “mane” that can best be described as a Mohawk hairstyle.

There are only four currently-recognized species of Comantella. C. pacifica is found from British Columbia south to Nevada and Utah. C. cristata is known from Idaho and California. C. rotgeri occurs in Colorado, New Mexico, and Alberta. C. fallei ranges in California and Colorado.

I expect to see more of these flies any day now. Last year I found this mating pair on March 12, but the winter was very warm. In all instances I have found Comantella perched on the ground (rarely on vegetation), usually on bare soil, in vast open fields.

Sources: Cannings, Robert A. 2012. “A Checklist of the Robber Flies (Diptera: Asilidae) of British Columbia,” University of British Columbia.
Cole, Frank R. 1969. The Flies of Western North America. Berkeley: University of California Press. 693 pp.
Dennis, D. Steve, Robert J. Lavigne, and Jeanne G. Dennis. 2012. “Spiders (Araneae) as Prey of Robber Flies (Diptera: Asilidae),” J. Entomol. Res. Soc. 14(1): 65-76.
Dennis, D. Steve, Jeffrey K. Barnes, and Lloyd Knutson. 2008. “Pupal cases of Nearctic robber flies (Diptera: Asilidae),” Zootaxa 1868. Auckland, New Zealand: Magnolia Press. 98 pp.

Hull, Frank M. 1962. Robber Flies of the World. Washington, DC: Smithsonian Institution Bulletin 224. 907 pp. (2 vols.).
James, Maurice T. 1941. “The Robber Flies of Colorado (Diptera, Asilidae),” J. Kans. Entomol. Soc. 14(1): 27-53.
Lavigne, R.J., William F. Barr, and G.M. Stephens. “Checklist of the Asilidae of Idaho,” College of Idaho. 26 pp.
Neslon, C. Riley. 1987. “Robber Flies of Utah (Diptera: Asilidae),” Great Basin Nat. 47(1): 38-90.

Monday, March 11, 2013

Moth Monday: Sophora Worm

One of the challenges I enjoy is matching caterpillars to their adult moths, and vice versa. Usually one of the two is spectacular and obvious, and the other is cryptic and/or scarce. Such was the case when I encountered the larvae known as the Sophora Worm, Uresiphita reversalis, of the family Crambidae.

I found many of the caterpillars amid their silken webbing on a common ornamental shrub in Tucson, Arizona on May 20, 2010. Turns out the plant was Texas Mountain Laurel, Sophora secundiflora, easily identified by its large, purple flowers and resulting robust pea-like pods. This is a native host for the moth, but the caterpillars are also known to eat non-native “broom” plants such as French Broom (Genista monspessulana), and other Genista species. This habit has given rise to an alternate name for the Sophora Worm: “Genista Broom Moth.”

Additional host plants include lupines (Lupinus), acacia (Acacia), false indigo (Baptisia), and other leguminous plants. It is also reported from Crapemyrtle (Lagerstroemia indica) and honeysuckle (Lonicera), but these are probably incidental.

The caterpillars feed out in the open, in groups, and during the day, in stark contrast to most caterpillars that are solitary and nocturnal, the better to avoid potential predators. The bold colors suggest that Uresiphita reversalis is distasteful to their enemies, and indeed they accumulate the toxins of their host plants for use in their own self-defense. They sequester the quinolizidine alkaloids found in their leguminous host plants, incorporating the chemicals into their exoskeleton. Even so, damsel bugs and other predatory insects with piercing-sucking mouthparts simply bypass this external defense by puncturing the cuticle and feeding on the internal tissues of the caterpillars (Bernays and Montllor, 1989).

The length of the life cycle of this species varies considerably depending on season and latitude. It can be as short as five weeks from egg to adult under optimal summer conditions in southern climes, and as long as 25 weeks in winter in the more northerly reaches of its range. There may be four or five generations annually. In Berkeley, California there are two major flight periods, one from March to May and the other from July to October. Overwintering usually occurs in the pupal stage, but adults are sometimes found during this season as well.

Eggs are laid in clusters (averaging about 19 per clutch in the lab) on the upper- or underside of leaves. The larvae go through five instars (an instar is the interval between molts). Pupation occurs inside an opaque, white cocoon woven amid dense webbing.

The adult moth has a wingspan of 27-34 millimeters. They are seen most often during the day and are easily startled from their resting place. The body and legs of the moth are bright white. The hind wings, usually not visible when the insect is at rest, are bright yellow or orange.

One reference asserts that the Sophora Worm is native to Mexico and the southwest U.S. and has spread with its hosts up the coast of California to the Bay area; and also north and east to the Great Lakes and mid-Atlantic states, even Maine and Nova Scotia. It became established in Los Angeles in 1930, spreading rapidly from there. By the 1980s it was spreading through the San Joaquin and Sacramento Valleys (Powell and Opler, 2009).

I didn’t find an adult moth until more than a year later. The specimen imaged here was in the same neighborhood where I found the caterpillars, on June 11, 2011.

Note that this moth was formerly classified in the family Pyralidae, and is often still placed there incorrectly on several internet resources. It is currently in the family Crambidae, subfamily Pyraustinae.

Sources: Bernays, E.A. and C.B. Montllor. 1989. “Aposematism of Uresiphita reversalis Larvae (Pyralidae),” J. Lep. Soc. 43(4): 261-273.
Leen, Rosemary. 1995. “Biology of Uresiphita reversalis (Guenée) and Comparison With U. polygonalis maorialis (Felder) (Crambidae),” J. Lep. Soc. 49(2): 163-170.
Powell, Jerry A. and Paul A. Opler. 2009. Moths of Western North America. Berkeley: University of California Press. 369 pp.

Sunday, March 10, 2013

Spider Sunday: Hololena Funnel-web weavers

Sometimes you go looking for spiders, and sometimes it seems they come looking for you. The second statement isn’t really true of course, but at the least you usually don’t have to go far to find arachnids. Here in the western United States, funnel-web weavers in the genus Hololena are abundant, even in the average yard or garden. Entire hedges can be full of their sheet-like webs.

Meanwhile, juvenile specimens, and mature males, will wander away from their webs, often straying indoors. It can be startling to suddenly have a spider appear on the wall while you are watching television.

Hololena is easily confused with other genera in the family Agelenidae, and to be fair it is only microscopic examination of certain body parts that can confirm the identity of any given specimen. Hololena is, however, readily separated from Agelenopsis based on the length of the spinnerets. Agelenopsis (and Calilena, too) have long spinnerets usually held parallel to each other. Hololena has short spinnerets, often directed somewhat inward toward each other.

These are medium-sized spiders, mature females ranging from 9-12 millimeters in body length, males 8-9 millimeters. Agelenopsis average substantially larger, about 10-20 millimeters. Most funnel-web weavers share a similar color pattern: two parallel or converging dark stripes on a pale carapace; a central reddish or brownish band running the length of the abdomen, often bordered by pale, wavy lines. The legs are often annulated (alternating bands of light and dark).

The genus Hololena appears to be restricted to the western third of the U.S., from Washington and Idaho south to southern California and New Mexico. There are approximately thirty recognized species, but the genus is in dire need of revision according to some arachnologists.

Agelenids in general spin thick, flat, hammock- or bowl-shaped webs with a funnel-like retreat in one corner. The web is not sticky. A tangle of threads above the silken platform intercepts flying insects, knocking them onto the sheet. The spider is extremely sensitive to vibrations and dashes out immediately to subdue its prey. It quickly drags the victim back into its lair to feed.

Male spiders have to approach females cautiously and deliberately. In Hololena, the male more or less bounces his legs and abdomen on the female’s web, creating a bout of one to six vibrations. A receptive female responds by drawing in her legs and lapsing into “cataleptic paralysis.” The male will draw closer and repeat his vibrational overtures until he is accepted or repelled. He then crawls over her back, gently grasping her two hind legs and dragging her deeper into her retreat.

Mating occurs when the male is able to turn the female on her side and insert one of his palps into her genital opening (epigynum). He repeatedly inserts his palp and pumps sperm into her before attempting to maneuver her into a position where he can insert the opposing palp. The female usually offers no resistance during this process. Once finished, the male grooms his palps and walks off the web. Occasionally his mate recovers from her paralysis prematurely and actively chases him off her web.

Mature males can be seen looking for females deep into the fall. The specimen shown above was observed on October 29, 2012 in Colorado Springs.

Researching this post I was startled to learn that there are confirmed cases of Hololena spiders biting people. It should be noted that actual spider bites are a pretty rare phenomenon, and the usual result is mild pain and swelling that doesn’t require medical treatment. Dr. Richard Vetter at the University of California, Riverside, published a note documenting three separate, verifiable instances of adult people who were bitten by Hololena spiders. Two were adult men, bitten by female spiders. The victims experienced headaches and four-hour episodes of vomiting. The third victim was an adult woman, bitten by a male spider, who experienced a very mild reaction. All three were perfectly fine in a matter of days without seeking medical attention (Vetter, 2012).

One need not be fearful of these spiders. I prefer to be enchanted by their delicate yet durable spinning work. I remember vividly a light snowfall we had here in Colorado Springs on October 25, 2012. The only place the flakes persisted was on Hololena spider webs. What an amazing scene! Take a look around your own neighborhood, especially on damp early mornings when dew has condensed. You will be amazed by the number of webs you hadn’t known were there.

Sources: Fraser, Jack B. 1987. “Courtship and copulatory behavior of the funnel-web spider, Hololena adnexa (Araneae, Agelenidae),” J. Arachnol. 15: 257-262.Vetter, R.S. 2012. “Envenomation by Spiders of the Genus Hololena (Araneae: Agelenidae),” Toxicon 60(3): 312-4.

Thursday, March 7, 2013

OrThoptera Thursday: California Angle-wing Katydid

In previous weeks I have written about the Greater Angle-wing Katydid and the Lesser Angle-wing Katydid, but there are four other species in the U.S. One of these, Microcentrum californicum, is found commonly in Arizona, and the length of California west of the Sierras.

The California Angle-wing Katydid is the smallest member of its genus, adults ranging from 41-52 millimeters. Note that the male has a brown stridulation area (its “shoulders”) like the Lesser Angle-wing, but its geographic range leaves no room for confusion.

The specimen shown here was attracted to a blacklight set up in Peppersauce Canyon in the Catalina Mountains of Pima County, Arizona on September 2, 2011. There was also a female Greater Angle-wing found in the same location on the same night.

The remaining Microcentrum species include M. louisianum, the Louisiania Angle-wing, found from Louisiana and Mississippi north through parts of Arkansas and Tennessee to the bootheel of Missouri. Microcentrum minus, the Texas Angle-wing, is found only in extreme south Texas; and the Southwestern Angle-wing, M. latifrons, is recorded from the Big Bend area of Texas and the southeast corner of Arizona.

>Sources: Capinera, John L., Ralph D. Scott, and Thomas J. Walker. 2004. Field Guide to Grasshoppers, Katydids, and Crickets of the United States. Ithaca: Comstock Publishing Associates (Cornell University Press). 249 pp.
Eades, David C., Daniel Otte, Maria Marta Cigliano, and Holger Braun. 2013. Orthoptera Species File Online. Version 5.0/5.0
Walker, Thomas J. and Thomas E. Moore. 2013. Singing Insects of North America. University of Florida.

Wednesday, March 6, 2013

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.

Monday, March 4, 2013

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.

Sunday, March 3, 2013

Spider Sunday: Flatties

Many spiders go unseen by the casual observer because they emerge only at night. Venture outside after dark, and you are likely to be astounded by arachnids you never knew existed. Take a flashlight to the outside walls of your own home and there will likely be spiders prowling across it. If you live in Florida or the southwest U.S., you will eventually see crab-like spiders of the family Selenopidae, called “flatties.”

I might not have recognized them myself were it not for Zack Lemann, Chief Entomologist at the Audubon Insectarium in New Orleans. We occasionally meet up in southern Arizona for the Invertebrates in Conservation and Education Conference at the end of July each year. In 2010, on a night field trip to Madera Canyon, Zack identified a spider sitting motionless on the outside of a restroom building as a “flattie.” I had figured it was a running crab spider in the family Philodromidae and appreciated the correction.

Flatties can be easily confused with any number of other spiders, but are readily identified by a few distinctive characteristics:

  • Extremely flattened appearance. They look like they have already been the victim of someone’s shoe, so flat are they. Even the legs look cock-eyed, oriented almost completely horizontal to the body. This distinctive leg configuration is called “laterigrade,” and only a few other spider families have this feature.
  • Legs increasingly longer from front to back. Note that in philodromid crab spiders like the one shown below the second pair of legs is the longest.
  • Six eyes in one row. Six of the spider’s eight eyes are in one row across its face. The other two set back on either side of the face.
  • Rear edge of sternum is notched. You have to turn the spider belly-up to see this character (good luck), but this feature of the “chest plate” is diagnostic.

Philodromid crab spider (note long 2nd pair of legs)

Their thin bodies allow flatties to slip into very narrow cracks and crevices, where they hide during the day. Most references indicate that these spiders hide under stones, or beneath bark on logs or trees, and between the bases of leaves of dense plants. I have personally never discovered them on the ground or under objects. They have always appeared on vertical surfaces at night in my experience.

These are medium-sized spiders, adults measuring from 7.5-13 millimeters in body length. Their sprawling legspan makes them appear larger. The mottled gray or brown or yellowish coloring helps to camouflage them on rock surfaces and tree trunks. They likely wait in ambush for prey, though when disturbed they can sprint with startling speed.

There are five species found north of Mexico, all in the genus Selenops. They collectively range from southern California to western Texas, and also in Florida and the Caribbean islands.

Sources: Jackman, John A. 1997. A Field Guide to Spiders & Scorpions of Texas. Houston: Gulf Publishing Company. 201 pp.
Kaston, B.J. 1978. How to Know the Spiders (3rd Ed.). Dubuque, IA: Wm. C. Brown Company Publishers. 272 pp.
Ubick, D., P. Paquin, P.E. Cushing, and V. Roth (eds). 2005. Spiders of North America: an identification manual. American Arachnological Society. 377 pp.

Friday, March 1, 2013

Fly Day Friday: Three-banded Robber Fly

Too often the first thing that pops into people’s minds when they hear the word “fly” is a house fly or a horse fly, or some other nuisance or pest fly. I think if the popular association were with robber flies, family Asilidae, public opinion of the Diptera would be vastly improved. Case in point is the little Three-banded Robber Fly, Stichopogon trifasciatus.

Far from being pests, or even pesky, robber flies are assassins of other insects, including the ones that bite and sting us. Many species are quite large, but the Three-banded Robber Fly is rather diminutive, measuring only 10-15 millimeters (and the top end of that spectrum might be generous).

Stichopogon trifasciatus is one of ten North American species in the genus Stichopogon, but the most widespread and easily recognized. It ranges from southern Canada to Central America, and coast to coast in North America. The bright silvery or blue-gray of the body, and distinct broad bands on the abdomen help set this fly apart from similar asilids. There is enough variation, however, to be somewhat confusing. The former species S. salinus, collected along the western edge of the Rockies from Idaho to northern Arizona, was recently synonymized with S. trifasciatus (Barnes, 2010).

The habitat and behavior of the Three-banded Robber Fly is suggestive of many tiger beetles. These flies like the beach! Well, rocky or gravelly beaches anyway. I have encountered them most frequently along the rocky edges of rivers and streams, but also well away from water. I found one in Colorado Springs on a rugged unpaved road. They like to be close to the ground, but on an elevated perch if possible. Startle one and, like a tiger beetle, it will take flight for a short distance before alighting again.

The adult flies feed mostly on other small flies, which according to one study amounted to 85% of their diet (true bugs, order Hemiptera, accounted for another 10%). Still, another observer noted that this species preys on small spiders to a large degree (Bromley, 1934). The fly attacks prey that is crawling on the ground, rather than intercepting it in flight as other species are known to do.

The life history of S trifasciatus remains mostly mysterious, but courtship behavior has been observed. The male apparently hovers back and forth before the female, his legs hanging and waving. He then attempts to copulate by pouncing on her (Preston-Mafham, 1993). Doesn’t sound like a romantic day at the beach, but….

Sources: Barnes, Jeffrey K. 2013. “The Genus Stichopogon Loew (Diptera: Asilidae) in America North of Mexico,” Proc. Entomol. Soc. Wash. 115(1): 9-36.
Barnes, Jeffrey K. 2010. “Revision of Nearctic Stichopogon Species (Diptera: Asilidae) With White-banded Abdomens, Including Description of Stichopogon venturiensis, New Species, From Coastal California,” Proc. Entomol. Soc. Wash. 112(3): 367-380.
Bromley, S.W. 1934. “The Robber Flies of Texas (Diptera: Asilidae),” Annals Entomol. Soc. Am. 27: 74-113.
Hull, Frank M. 1962. Robber Flies of the World. Washington, DC: Smithsonian Institution Bulletin 224, Parts 1 and 2. 907 pp.
Preston-Mafham, Rod and Ken. 1993. The Encyclopedia of Land Invertebrate Behaviour. Cambridge, Massachusetts: The MIT Press. 320 pp.
Raney, Herschel. 2003. “Stichopogon Page,” Random Natural Acts