Wasp Wednesay: Hemipepsis ustulata

The term “tarantula hawk” applies to more than one species of large wasp. It even applies to more than one genus. Here in the United States, the genera Pepsis and Hemipepsis are the only tarantula hawks, and the largest of our spider wasps in the family Pompilidae. Hemipepsis ustulata is a common species across much of the western U.S., one I have encountered in both Arizona and Colorado.

It is not easy to separate Hemipepsis from Pepsis, but I find that Hemipepsis are matte black in color, not the iridescent blue-black that their relatives are. Hemipepsis also tends to fly earlier in the season than Pepsis, especially in the southwest, but both genera can be found together in the fall, Hemipepsis being in the second generation in autumn. Wing venation is apparently the only sure way to tell the two apart, but most folks understandably don’t want to get that close to such a large, stinging insect to find out which is which.

Tarantula hawks in general have interesting behaviors, especially the males. Dr. John Alcock has studied in-depth the territorial behavior of male Hemipepsis ustulata in the Superstition Mountains near Phoenix, Arizona. They are among the first insects seen in spring, but as the season wears on they become early risers, taking advantage of the brief window of time when Sonoran Desert temperatures are not too cool, but not incinerating, either. They are looking for prominent outposts, often Palo Verde trees atop hills.

Once a male wasp claims a lookout tree, it vigorously defends it from competing males. Most interactions consist of the resident male flying off his perch in a brief foray to chase away the intruder. There is usually only feeble resistance, if any, from the interloper. Males that have been displaced from their own territories, however, are more likely to try and displace another male. This takes the form of long, ascending flights in which the wasps spiral around each other as they climb to heights of thirty feet or more. Sometimes they escalate to altitudes where they can no longer be observed without binoculars.

These aerial duels are contests of both endurance and speed. The faster and fitter male is thus the one more likely to win.

Female wasps cruising past an occupied tree elicit an entirely different response. The resident male gives chase and, if he successfully reaches her, attempts to couple with her in the air and descend to the ground. There, they mate briefly if she is receptive. The male then returns to his perch, which he hopes has not been claimed by another male while he was um, otherwise engaged.

This form of territoriality is called “landmark defense,” and it is the strategy of choice in situations where defense of a resource used by females is impractical or impossible. While blooming palo verde trees might seem to be a nectar source for female tarantula hawks (and they are, for Pepsis chrysothemis), females of Hemipepsis ustulata seem to prefer the flowers of creosote bush, which has a wide and scattered distribution in the landscape.

Once mated, a female tarantula hawk goes about the business of finding occupied tarantula burrows and baiting the spider into battle aboveground. These burrows are also widely scattered. So, male wasps can’t stake out a tarantula “colony” because there is no such thing, at least not for spiders the size needed by the female wasp.

Some of the hunting activities of these wasps may take place at night, or at least at dusk, for I have found females in southeast Arizona coming to blacklights at night. I have also found females feeding on oozing sap of Desert Broom (Baccharis sarothroides). Here in Colorado Springs I have seen both genders at a blooming saltcedar tree (Tamarix sp.), though the female simply circled the tree and flew off again.

Hemipepsis ustulata ranges from southern California east through Nevada to Texas, Oklahoma, and Kansas. It would be well worth it to accumulate more records of this species. More county records are certainly possible, and perhaps state records, too.

Sources: Alcock, John. 1984. “Ridgetop Rendezvous,” Natural History 93: 42-47.
Evans, Howard E. 1997. “Spider Wasps of Colorado (Hymenoptera, Pompilidae): An Annotated Checklist,” Great Basin Naturalist 57(3): 189-197.

Spider Sunday: Phidippus octopunctatus

If the spider world ever had a beauty contest, the winner would likely be a jumping spider in the family Salticidae. Some are clad in the equivalent of clown suits, others in camo, but many seem to have a fashion sense that would be the envy of any human clothing designer. Such is the case with males of the species Phidippus octopunctatus.

The species name might suggest that it would have eight spots (octo=eight, punctatus=punctures or spots), but this is not so. The male, a sizeable, densely hairy spider averaging 9.35 millimeters in body length, is black underneath, with black legs, and a beautiful silvery gray above. Females, slightly larger in size at 10.19 millimeters, are uniformly gray or beige. The spiderlings may have a vaguely striped pattern on the abdomen, but otherwise look similar to the adults.

This color scheme may benefit the spider, as some species of velvet ants are very similar. Velvet ants are solitary wasps, the females of which are wingless, and capable of an excruciating sting in self-defense. Potential predators quickly learn to steer clear of velvet ants; and other arthropods that mimic velvet ants would also be avoided.

Velvet ants and Phidippus octopunctatus also favor the same kind of habitat: prairies, grasslands, deserts, and open fields. The spider ranges over most of the western U.S., from southeast Washington to California and east to Iowa, Missouri, and Texas. It also occurs in northern Mexico.

This is one wary animal, and getting images of wild individuals is a real challenge. They see you coming from a mile away (well, ok, at least a couple of yards), and dodge behind a yucca blade or quickly descend into undergrowth. Catching one out in the open, as I did in Stratton Open Space in Colorado Springs on June 1, 2012, is no guarantee of a good shot, either. They make a run for it as soon as they see you.

There are some truly spectacular images of this species by Mark Chappell of the University of California, Riverside. Note that the jaws are not metallic green or red as they are in other Phidippus species. Males may be territorial, as evidenced by the intimidating display shown in one of Mark’s images.

I encourage my readers to look for this species, as its geographic distribution is rather sketchy. No records appear to exist for Oregon, Idaho, or Wyoming for example. Adult specimens are usually found in summer, but their longevity is unknown. Do they live longer than one year? What does their courtship ritual look like? Your images, videos, observations, and notes could greatly illuminate our view of this spider.

Sources: Edwards, G.B. 2004. “Revision of the Jumping Spiders of the Genus Phidippus (Araneae: Salticidae),” Occasional Papers of the Florida State Collection of Arthropods 11:1-156.
Metzner, Heiko. 2012. Jumping Spiders (Arachnida: Araneae: Salticidae) of the World.
Proszynski, Jerzy. 2003. Salticidae (Aranae) of the World. Museum and Institute of Zoology, Polish Academy of Sciences.

Fly Day Friday: Greater Bee Fly

Spring is just around the corner here in the northern hemisphere, and one of the first insects you are likely to see is a buzzing fuzzy ball looking for nectar and moisture. That would be the Greater Bee Fly, Bombylius major. It is perhaps the most familiar and abundant member of the family Bombyliidae found in North America, Europe, the Middle East, and temperate Asia.

People unfamiliar with bee flies might interpret the long beak as a device for sucking blood, and identify the fly as some kind of mutant, hairy mosquito. Nothing could be farther from the truth. Those long mouthparts allow the fly to reach nectar deep inside some flowers, even while the fly may be hovering in front of the blossom.

That hovering behavior is yet another hallmark of bee flies in general, but this species especially. The territorial males are so accomplished that I was able to take images of one hovering about 2-3 feet off the ground at the Tucson Botanical Gardens in Arizona on March 24, 2010.

Also known as the “Large Bee Fly,” Bombylius major is not exceptionally big. Adults measure 12-18 millimeters, with a wingspan of up to 25 millimeters. Many other bee flies are larger. Size varies according to the degree of nutrition consumed in the larval stage.

Despite the familiarity of this species, surprisingly little is known about its life cycle. It is definitely parasitic in the larval stage, and so far the only known hosts are solitary bees in the genera Andrena (“mining bees”), Colletes (“plasterer bees”), and Halictus (“sweat bees”). This fits with the presence of the adult bee flies in the early spring, as that is also when female mining bees are excavating burrows and provisioning the underground cells with pollen and nectar.

© Eric R. Eaton

The female fly locates an open nest burrow of its host and supposedly hovers over it, lobbing eggs down the tunnel with flicks of her abdomen. The larva that hatches from each egg then actively seeks out an individual cell with a larval bee. The fly maggot then waits patiently while the host eats the pollen and nectar ball, growing large and plump just before it pupates. Then the maggot makes its move, attaching itself to the exterior of the bee larva. There it feeds as an external parasite, eventually killing its victim.

The mature fly larva then pupates, usually spending the winter in that stage. Scientists in Sweden have noted that pupae occasionally pass two winters before the adult fly emerges (McAlister, 2013). The pupa is armed with hooks, spines, and stiff bristles (setae) that it uses to work its way through the soil plug closing the bee’s burrow. Upon reaching the surface, the adult fly breaks out of the pupal exoskeleton, leaving it behind.

Look for these flies in yards, gardens, forest edges, sunny spots in woodlands, and similar situations. This species, which also goes by the names “Dark-edged Bee Fly” and “Black-tailed Bee Fly,” is flying mostly between March and June, but is especially common in April and May. They are at least potentially important pollinators of a number of wildflowers such as Gilia.

Sources: Cole, Frank R. 1969. The Flies of Western North America. Berkeley: University of California Press. 693 pp.
Hull, Frank M. 1973. Bee Flies of the World. Washington, DC: Smithsonian Institution Press. 687 pp.
McAlister, Erica. 2013. “Bombylius major (Large Bee Fly),” Nature Online, Natural History Museum (UK).
Talibart, Rachael. 2012. “Bee Fly,” Focused Moments.

True Bug Tuesday: Brown Marmorated Stink Bug

Ok, ok, I confess. I watch that awful Animal Planet show Infested! What is often more appalling than the crises faced by the people showcased in the program are the rampant errors and hyperbole provided by many of the “experts.” One recent episode, however, was probably not overly exaggerated. It featured a family whose rural Pennsylvania home was overrun with Brown Marmorated Stink Bugs, Hyalomorpha halys, that were seeking winter shelter.

I have written about this invasive species previously, in a feature on ”Common Indoor Insects of Autumn”, having never seen one in person. That changed last year when my wife and I visited Cape May, New Jersey. Many structures, from buildings to Port-O-Lets, were being investigated by the bugs as potential winter hang-outs. The insects were also common on foliage and vehicles.

Since my first article, things have gotten even worse. H. halys is now found in most states east of the Mississippi River, plus the Pacific Coast states, and now Utah. Furthermore, it has elevated its status to that of a bonafide agricultural pest. In fact, it is essentially number one on the U.S. Department of Agriculture’s “most wanted” list.

The Brown Marmorated Stink Bug is what is called a “generalist” feeder, meaning that there are a wide variety of plants on its menu. Most insects are “host-specific,” unable to eat plants outside of one genus or family. The Monarch butterfly is a good example of a host-specific insect. The caterpillars can only eat the foliage of milkweed and closely-related plants. Contrast this picky diet with that of H. halys. Over 300 species of plants are palatable to it in the nymph and adult stages.

This versatility in host plants translates to a potent economic impact. The bug accounted for $37 million in losses to apple-growers alone in 2010. Other crops adversely affected include raspberries and blackberries; and organic farmers reported losses of beans, peppers, and tomatoes. The cosmetic damage alone can render some produce unsalable.

Like all true bugs, stink bugs feed on plant sap and juices through beak-like piercing-sucking mouthparts. Their sipping and sucking can cave-in corn kernels, wither fruits, and leave unsightly stains behind.

Adult male Brown Marmorated Stink Bugs also emit an “aggregation pheromone,” a kind of aromatic chemical cocktail that attracts other males, females, and nymphs to food sources. So, as if a single bug isn’t bad enough, he recruits friends and family. Scientists may be getting closer to using that pheromone as a weapon against the bug, by drawing them into traps, for example.

Back to that episode of Infested!. It had a happy ending. Initially demoralized by the overwhelming number of bugs holding them prisoner indoors and eventually infiltrating their home, the family turned the problem into profit. The father devised a light trap to attract and kill the bugs, and is now selling his invention to others.

Sources: Gibson, Caitlin. 2013. “Stink bugs could mount a comeback this spring,” The Washington Post, January 5, 2013.
Murray, Todd, et. Al. 2012. Pest Watch: Brown Marmorated Stink Bug. Washington State University Extension Fact Sheet FS079E. 5 pp..

Spider Sunday: Foreign Spider Now in Florida

Surprise, surprise, surprise, yet another exotic invader has recently been discovered in the Sunshine State. When you have pythons, tegu lizards, and other alien animals roaming free and reproducing in the swamps, a tiny arachnid might seem to be no big deal. Still, it is symptomatic of greater problems in protecting our native ecology that extend beyond lax regulation of the pet trade. This particular species, Cithaeron praedonius, is native to the Old World, from western Africa (Gambia), to Greece, Libya, and Malaysia. It is an accidental introduction to Australia and Brazil (Carvalho, et al., 2007). The first report of this species in the U.S. came from Port Richey in Pasco County, Florida, in February, 2011.

© "MrWheeler" via Bugguide.net

The manner in which the Florida record was revealed reflects the importance of citizen scientists and the power of the internet. A member of the Arachnoboards online community posted images of a spider he had found and that he was having trouble identifying. He then enlisted the help of Florida arachnologist G.B. Edwards. The mystery was solved in part when another Arachnoboards member located in Italy suggested the species. Specimens subsequently sent to Edwards allowed him to confirm the identification conclusively (Edwards & Stiles, 2011).

Whether this was an isolated incident of introduction seems to have been answered with a “no,” as another record was reported this last week on Bugguide.net, another influential internet resource for identifying North American insects and other arthropods. The location this time is Winter Springs, a suburb of Orlando, in Seminole County, Florida.

Cithaeron praedonius is a spider that hunts “on foot,” rather than spinning a web and waiting for prey to be intercepted by the silken snare. In fact, this species may be a specialized predator of other spiders. Observations have shown that in the first Florida case, the live specimens in captivity readily fed on native cobweb weavers, as well as juvenile Brown Widow spiders. Given its nomadic nature, perhaps the species has already spread to neighboring counties from the Port Richey location.

© "MrWheeler" via Bugguide.net

The spider is clearly reproducing, as flat, round egg sacs were found at the Pasco County location. Spiders of different ages were also observed. Each spider creates a silken “nest” in which to molt, and perhaps rest when it is not actively hunting. Otherwise, the spider dispenses with silk in its daily life.

These are small spiders, mature females averaging about 5 millimeters in body length, males about 3 millimeters. The compact arrangement of the eyes might fool one into thinking they might be juvenile males of the Southern House Spider, Kukulcania hibernalis. Worse yet, they could be mistaken for young recluse spiders (Loxosceles sp.).

© "MrWheeler" via Bugguide.net

If you have seen Cithaeron praedonius, or any other unfamiliar spider, consider taking clear images and submitting them to Bugguide, or Project Noah, or another community where scientists and the public interact. Securing specimens and preserving them in ethyl alcohol, along with a label noting the date and location of capture (plus the collector’s name), is tremendously important in confirming identifications later.

Our invasive species have many points of origin and many avenues of access to new territories thanks to unregulated (free?) trade, our internationally mobile society, and our fascination with organisms both floral and faunal, from foreign soils. Perhaps we should be more satisfied with the life that lives here already, and how we can better protect it from exotic competition.

Sources: Carvalho, Leonardo S., Alexandre B. Bonaldo, and Antonio D. Brescovit. 2007. “The first record of the family Cithaeronidae (Araneae, Gnaphosoidea) to the new world,” Revista Brasileira de Zoologica 24(2): 512-514.
Edwards, G.B. and Joe T. Stiles. 2011. “The first North American records of the synanthropic spider Cithaeron praedonius O.P.-Cambridge (Araneae: Gnaphosoidea: Cithaeronidae), with notes on its biology,” Insecta Mundi 0187: 1-7.

Wasp Wednesday: Great Black Wasp

Few North American wasps are as conspicuous as the Great Black Wasp, Sphex pensylvanicus. This all-black insect with violet reflections on its wings is so large as to sometimes be mistaken for a tarantula hawk wasp. Males average 22 millimeters in body length, while females are about 28 millimeters (up to 35 mm) and more robust.

This is also a common and widespread species, ranging from southeast Canada to northern Mexico, and as far west as southern California. It is absent from the Pacific Northwest, and while I lived in Arizona for a decade, I did not encounter this species there, either. It is perhaps most abundant along forest edges in deciduous woodlands, sumac thickets, gardens, and fields with scattered trees.

Habitat preference is governed by the need for the adult wasps to find flower nectar to fuel their flight; and for females to find katydid prey. Milkweed (Asclepias spp.), thoroughworts (Eupatorium spp.), mountain mint (Pycnanthemum spp.), buttonbush (Cephalanthus occidentalis), camphorweed (Pluchea spp.), Rattlesnake Master (Eryngium yuccifolium), White Sweet Clover (Melilotus alba), and goldenrod (Solidago spp.) are among this wasp’s favorite rest stops. Females dig burrows in soft soil, usually in sheltered spots such as the dirt floors of abandoned barns or other outbuildings.

Though they are solitary, several females may nest in close proximity to one other. Each burrow is an angled tunnel about an inch in diameter and over one foot long. At the end of the burrow is a chamber from which other cells are added over time. The female leaves the nest entrance open while she goes about finding katydids. Her prey can be enormous. Adult Greater Angle-wing Katydids (Microcentrum rhombifolium) can be 52-63 millimeters long and are quite heavy. The Lesser Angle-wing Katydid (M. retinerve) is another prey species, as is Scudderia furcata, the Fork-tailed Bush Katydid. An average of three paralyzed katydids goes into each cell in the nest, a single egg being laid on the first of those victims.

Greater Angle-wing Katydid female

The wasp larva that hatches from the egg feeds and grows for about ten days, eventually reaching a length of 30-35 millimeters, and a diameter of 7-10 millimeters. Larval insects are almost always larger than the adult stage because so much energy is spent in the pupal stage. The larva probably passes the winter in a pre-pupal state, pupating the following spring and then emerging in summer.

Female Great Black Wasps are incredibly successful at finding katydids. One field researcher, Reverend John A. Frisch of Woodstock College in Maryland plugged the nest entrances in one aggregation. The result was 252 katydids piled up in only five days. That worked out to an average of nearly 17 katydids per wasp per day (Evans, 1963). The wasps fly with that heavy load, too.

Hauling a large, heavy katydid back to the nest can attract unwanted attention, and one entomologist in Rhode Island observed House Sparrows (Passer domesticus) and, to a lesser degree, Gray Catbirds (Dumetella carolinensis) intercepting female wasps and relieving them of their paralyzed prey. As many as one-third of return trips by all the female wasps observed ended this way: empty-handed (Benntinen & Preisser, 2009).

The adult wasps themselves can be parasitized by Paraxenos westwoodi, one of the insects called stylopids or “twisted-wing parasites.” Wasps that have deformities of the abdominal segments, often with a bullet-like capsule or two protruding between segments, are victims of stylopids.

An interesting piece of historical trivia is that this species was the first insect subject of a paper by a naturalist native to North America. Observations of the Great Black Wasp by John Bartram (Philadelphia) were presented to the Royal Society (Royal Society of London for Improving Natural Knowledge) by Peter Collinson in 1749. The species was not officially described until 1763 by Carl Linnaeus.

Sources: Benntinen, Justin and Evan Preisser. 2009. “Avian kleptoparasitism of the digger wasp Sphex pensylvanicus,” Can. Ent. 141(6): 604-608.
Evans, Howard E. 1963. Wasp Farm. Ithaca, NY: Comstock Publishing Associates (Cornell University Press). 178 pp.

Spider Sunday: Orchard Orbweaver

People who think all spiders are creepy, and have no beauty about them whatsoever have never seen an Orchard Orbweaver, Leucauge venusta. This member of the family Tetragnathidae is pearly white or silvery with black, yellow, and red markings, and green legs. It is a truly lovely animal.

The Orchard Orbweaver is one of two species in the genus Leucauge found in North America north of Mexico. The other is L. argyra, found only in Florida. L. venusta occurs from southern Ontario, Canada to Florida, and east to Nebraska and eastern Texas. It also ranges as far south as Panama. I have encountered them in Ohio, Massachusetts, and South Carolina.

Despite its common name, it is not terribly common in orchards, preferring woodland habitats where it builds a horizontal orb web in shrubs, and bushes. Younger spiders have their webs closer to the ground, while adults spin them about 1.5 meters high. The web of an adult spans roughly twelve inches, and features an average of 30 radii (“spokes”) and more than sixty spirals.

The spider hangs upside down in the hub (center) of its snare, displaying a mostly black underside with a red crescent or rectangular spot. Unfortunately, many people mistake the Orchard Orbweaver for a black widow because of that red marking. However, widow spiders are almost never out in their webs during the day, and widows build tangled webs, not orbs.

It is also easy to mistake this species for orb weavers in the genus Mangora, but those spiders spin a vertical orb web, not a horizontal one. The Basilica Spider is also similar, and spins a horizontal orb web, but the orb is pulled into a dome shape. Finally, many sheetweb weavers in the family Linyphiidae resemble Leucauge venusta, but none of them spin orb webs.

Mature females of the Orchard Orbweaver measure 5.5-7.5 millimeters in body length, and males 3.5-4 millimeters. Individuals overwinter as sub-adults, hiding in leaf litter and under loose bark. Adults are found most abundantly in late spring and early summer, perhaps avoiding competition with other web-building spiders that mature later in the season.

The Orchard Orbweaver is shy, and drops from its web straight to the ground if it feels threatened, often disappearing into leaf litter and undergrowth. Don’t let that deter you from looking for it. These are highly photogenic spiders.

Sources: Gaddy, L.L. 2009. Spiders of the Carolinas. Duluth, MN: Kollath+Stensaas Publishing. 208 pp.
Jackman, John A. 1997. A Field Guide to Spiders & Scorpions of Texas. Houston: Gulf Publishing Co. 201 pp.
Jones, Janson. 2011. “Leucauge venusta (Orchard Orbweaver),” Dust Tracks on the Web
Weber, Larry. 2003. Spiders of the North Woods. Duluth, MN: Kollath+Stensaas Publishing. 205 pp.

Fly Day Friday: Cluster Flies

Note: This is the debut installment of a semi-regular feature I am dubbing “Fly Day Friday.” It should be noted that the concept of “Fly Day Friday” originated as a group on the photo-sharing website Flickr. I hope that what I offer here is viewed as a complement to that Flickr group and not as an attempt to usurp what they have going there.

On warm winter days, you may be disturbed to find several medium-sized flies bumbling against your window panes, especially if you live in a rural area. Where did they come from? Why are they active at such a cold time of the year? Exactly what are they? House flies?

They are probably blow flies in the family Calliphoridae; specifically, “cluster flies” in the genus Pollenia. While most blow flies are associated with rotting animal carcasses, cluster flies have an entirely different life cycle: depending on the species, they are parasites or predators of earthworms, or parasites of caterpillars, bees, or other insects.

Until fairly recently, it was thought that there was only one species in North America: Pollenia rudis. Now, six species are recognized, differentiated by minute characteristics not generally visible in images of living specimens in the field. The number, position, and length of setae (stiff hairs or bristles) on various body parts are key characters (Jewiss-Gaines, et al., 2012).

During the spring and summer, cluster flies are most often seen on flowers like Queen Anne’s Lace (Daucus carrota), where they are sipping nectar. They can be easily mistaken for overgrown house flies, but fresh specimens have a coating of golden hairs on the thorax. These hairs are easily abraded, however, so older specimens often lack this glistening quality. I have also seen cluster flies lapping up “honeydew,” the sweet liquid waste of aphids and scale insects. The flies will flit from leaf to leaf, eagerly sopping up the sticky goodness with sponge-like mouthparts at the tip of their elbowed proboscis.

Once cooler temperatures set in, Pollenia enjoy basking on the sunny side of buildings, like other kinds of blow flies do. They prefer white structures, or other pale colors that reflect the heat. Eventually, the flies seek shelter for the winter, and this is when they become a nuisance.

Despite their robust appearance, they are adept at squeezing into small openings that permit their entry into window frames, wall voids, and other snug niches. There, they can pile up by the hundreds, especially in older homes. They usually stay there until the weather warms again, when they exit without fanfare. Unseasonable temperatures in mid-winter may cause them to stir, however, and they can become disoriented, finding their way inside rooms where they fly aimlessly with an irritatingly loud buzz.

Cluster flies thankfully do no harm to people or pets. They carry no diseases that we know of, and are decidedly only a “nuisance pest.” Smashing one can leave a greasy stain on the wall, though.

The life history of the earthworm parasites is well known. Female flies lay their eggs in early spring, depositing two or three at a time in the soil. The larvae hatch in four to six days and begin searching for their earthworm hosts. A larva enters the worm through the male genital perforation, or close to it. For about the next two weeks, the maggot feeds inside the earthworm, periodically punching a hole in the worm’s body wall to take a breath of air. Ironically, the maggot’s spiracles (breathing holes) are located on its rear end, so it must stick its butt out the worm’s body to breathe.

Once it has matured, the fly larva exits the worm (usually the worm is still alive at this point), and pupates in the soil. The fly pupa is encased the last larval skin, which is hardened into a capsule-like structure. The pupal stage takes from 39-45 days, after which the adult fly bursts from its capsule. The cycle is then repeated, for up to four annual generations.

Pollenia rudis probably originated in Europe. How do we know this? Nearly all native earthworms in North America were wiped out by glaciers during the ice age. The overwhelming majority of worms you see today are European immigrants that found their way across the Atlantic in the soil used for ships’ ballast in those vessels that brought our own ancestors here.

Pollenia rudis and P. pediculata are by far the most common cluster flies you are likely to encounter in the U.S. and Canada. Pollenia vagabunda and P. labialis are likely recent introductions from Europe (1950s and 1960s).

Take a closer look at that “house fly” the next time you see one. It is probably a cluster fly instead. House flies are smaller, with bright white faces. See how many other flies you can find on the inside and outside of your own home. You might be surprised at the biodiversity you make no effort to support.

Sources: Berenbaum, May R. 1989. Ninety-nine Gnats, Nits, and Nibblers. Urbana: University of Illinois Press. 263 pp.
Jewiss-Gaines, Adam, Stephen A. Marshall, and Terry L. Whitworth. 2012. “Cluster Flies (Calliphoridae: Polleniinae: Pollenia) of North America,” Canadian Journal of Arthopod Identification No. 19. 22 pp (pdf file).

True Bug Tuesday: Masked Hunter

Note: This is the debut installment of a semi-regular feature I am dubbing “True Bug Tuesday.” It will likely include reposts of previous entries that cover members of the order Hemiptera.

Remember when your parents told you there were no monsters under your bed? Perhaps they were wrong. Have you ever wondered if you were hallucinating when you swore you saw a self-propelled dust bunny crawling across the floor? You might have been perfectly sane. There is a predatory insect that qualifies as both a miniature monster and an animated dust ball, and it is most often encountered indoors rather than outside.

The Masked Hunter, Reduvius personatus, is a member of the assassin bug family Reduviidae. Fortunately, the only thing it “assassinates” is other insects and related invertebrates. The piercing-sucking mouthparts are sleeved inside a short, stout, segmented beak bent under the insect’s “chin” when not in use.

The most remarkable trait of this species is the appearance of the immature stages, called “nymphs.” True bugs in general go through “gradual” metamorphosis, such that the juvenile stages look much like the adults, except that they are smaller, not sexually mature, and lack wings (if the species in question has wings at maturity). This is true of the Masked Hunter, except that the nymphs actively cover themselves in lint, sawdust, and other debris.

Their bodies are covered in short and long trichomes (hairs) connected to glands that produce a sticky substance. Fine particles adhere to the short trichomes close to the body of the insect, while longer trichomes anchor coarser particles in a second layer of camouflage. A “tarsal fan” of dense, long hairs on the foot of each hind leg helps the nymph apply the trash to the trichomes (Weirauch, 2006).

Each time the baby assassin molts (sheds its exoskeleton to grow in the brief interval before the new exoskeleton hardens), it must repeat the self-decorating process. The disguise helps protect it from potential predators, but might also make it appear harmless to its own prey. The Masked Hunter is probably a generalist predator, but it is often found in association with people and/or colonial birds and bats. It is well known for preying on bed bugs and swallow bugs (true bugs in the family Cimicidae). Other prey records include silverfish, booklice, and at least one harvestman (Arachnida: Opiliones).

Masked Hunters go through five instars. An instar is the period between molts. The nymphs are the ones that overwinter, usually in the fifth instar, but in Canada the life cycle may take two years, the nymphs overwintering in the third and fifth instar (Scudder, 1992). During the winter they are in diapauses, ceasing activity until the following spring. The sixth molt produces the adult insect, a dark, winged animal measuring from 15-22 millimeters in length.

Today, the Masked Hunter is found throughout the Northern Hemisphere. It is assumed that it is European in origin and has been transported to other continents through human travel and commerce. While it can be a common species, it is not prolific, and populations are usually small. Few specimens will occupy any given home or other building.

Assassin bugs are able to produce sound by rubbing one body part against another, a phenomenon known as “stridulation.” In this case, the insect rocks its head up and down, rubbing the tip of its beak across a series of transverse ridges on its "chest." The result is a very audible squeaking sound that may startle any other creature that grabs the bug.

The Masked Hunter is found throughout the Northern Hemisphere. It is assumed to be European in origin and has been transported to other continents through human travel and commerce. Most adult specimens of Reduvius personatus are seen in June and July. Look for them at lights at night where they are occasionally attracted by the buffet of potential prey insects. By day, they hide under bark on logs and in other sheltered situations. Be careful, though, Masked Hunters can deliver a painful bite in self-defense.

Sources: Hoffman, Richard L. 2006. “Assassin Bugs of Virginia,” The Insects of Virginia 15: 1-74.
Scudder, G.G.E. 1992. “The distribution and life cycle of Reduvius personatus (L.) (Hemiptera: Reduviidae) in Canada,” J. Entomol. Soc. B.C. 89: 38-42.
Weirauch, Chrstiane. 2006. “Anatomy of Disguise: Camouflaging Structures in Nymphs of Some Reduviidae (Heteroptera),” Am. Mus. Novit. 3542: 1-18.

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.