Saturday, October 18, 2014

"Doodlebugs" (Antlions)

Growing up in Oregon, all I knew initially of antlions was what I read in books. The insects are members of the family Myrmeleontidae in the order Neuroptera. So, they are related to lacewings, mantispids, spongillaflies, and their kin. I wasn't even sure antlions could be found in the Pacific Northwest, but I was fascinated by the "pits" that the larvae supposedly dug to trap ants and other insects.

Adult antlion, Colorado

The images in books never gave a sense of scale, so I imagined that the funnel-like holes must approach the size of a saucer. Ha! Most antlion pits are about the diameter of a quarter, as shown in the image below.

"Standard size" Myrmeleon pits on gentle slope, Colorado

Sometimes they are larger, but the size of the crater does not correspond to the size of the larva that digs it. The breadth and depth has more to do with soil texture, and whether there is a slope or not.

Larger Myrmeleon pits on steeper slope, Colorado

Antlion larvae might be considered among the ugliest and/or most terrifying of insects, and indeed they must be to their victims. Most are about the size of a large pea, but they are wrinkly, studded with spines, and with spindly legs. Their most remarkable feature is a pair of long, hooked mandibles.

Antlion larva, Kansas

Ironically, these mini-monsters are best known by the cute moniker of "doodlebugs." They can create random, cursive "doodles" in sand in the process of finding a new place to dig a pit, and that may be the source of the colloquial name.

Actually, it is only larvae of the genus Myrmeleon that make the trademark pits here in North America. Pretty much all the other genera simply bury themselves just below the surface of the soil and wait with jaws agape for a hapless insect to pass by.

Antlion larva, Colorado

Myrmeleon larvae can only walk backwards, but they do so rapidly. They dig a pit by walking in reverse, and in a spiral, throwing sand with their jaws and the flattened top of their head. They then lie in wait beneath the soil at the very bottom of the pit. The sloping sides of the funnel are highly unstable and any small insect that reaches the lip of the trap begins descending immediately. The larva senses the vibrations and throws additional sand onto the victim to hasten its doom.

The jaws of a doodlebug are hollow, and the larva injects a cocktail of enzymes that paralyzes its victim and begins extra-oral digestion of its tissues. The doodlebug then reverses flow, imbibing the liquified innards of its prey. The resulting dry carcass is then catapulted out of the pit with a violent thrust of the antlion's head.

Scotoleon nigrilabris female, Colorado

Doodlebugs more than make up for the horrid appearance of their youth by metamorphosing into delicate, slender, lacy-winged adults that superficially resemble damselflies. These fairy-like insects fly clumsily, and are most often seen among tall grasses, especially at dusk.

Myrmeleon immaculatus, Massachusetts

Note the short, thick, clubbed antennae that instantly distinguish them from damselflies. Males frequently have a much longer abdomen, tipped with bracket-like claspers. This is especially true of the genus Scotoleon.

Adult male Scotoleon, Arizona

Despite the fact that adult antlions are fairly large, they are ridiculously cryptic. I have personally witnessed flying antlions alight on grass stems or twigs, and instantly align themselves so perfectly as to be essentially invisible. Dark spots and speckles on the wings break up their outline, but they also flatten themselves seamlessly against the substrate.

Myrmeleon exitialis, Colorado

There are eighteen (18) genera of antlions recorded north of Mexico, with 94 species. Some are truly spectacular, like the three species in the genus Glenurus that sport black, white, and pink wingtips.

Glenurus luniger, Arizona

The genus Vella includes three species, which are true giants. Adults have a wingspan of 100-120 millimeters or more. They are found in about the southern third of the U.S., and are frequently attracted to lights at night.

Vella americana, Texas

Look for the larval pits of Myrmeleon in fine, powdery soil, or sawdust around rotten logs. Where there is one there are usually several. Prime situations for such colonies are at the base of trees, beneath rock overhangs, under bridges, the dirt floor of old barns and sheds, and any other situation that remains perpetually dry. They can be in exposed situations, but I find that is rarely the case.

Myrmeleon pits under a rock overhang, Arizona

Watch for adult antlions at your porch light at night.

You can tickle doodlebugs at the bottom of their pit with a grassblade or twig, and get them to throw sand or grab the offending object. You can also keep them in captivity by providing a fairly deep container of fine sand and periodically dropping in ants and other invertebrates. They can take down surprisingly large prey.

Adult antlion, Ohio

Antlions pupate inside a silken capsule the larva spins underground, incorporating grains of sand into the cocoon.

Enjoy looking for, and observing, these amazing insects, then share your story here, on Facebook, or elsewhere, like The Antlion Pit (though I am not certain this is still an active website).

Brachynemurus abdominalis, Massachusetts

Tuesday, October 14, 2014

Carpet Beetles, Genus Anthrenus

As a volunteer answer-man for AllExperts.com, I receive many questions pertaining to carpet beetles, tiny coleopterans in the family Dermestidae. In fact, I venture to say that at least seventy percent of the queries I get are related to carpet beetles and their larvae. Ironically, I now live in a region where these beetles are relatively scarce.

Anthrenus sp. larva, Colorado

Yesterday, I finally found a living larva of the most troublesome genus most people find: Anthrenus. The hairy grub was only about four millimeters in length, and crawling up the bathroom wall. This is an unfortunate commentary on our housekeeping habits, I suppose, but even the cleanest homes will have carpet beetles at one time or another. It takes precious little to feed them.

Carpet beetle larvae eat all manner of dried animal products, especially the shed hair and skin cells of pets and people. This food supply accumulates faster than you might imagine and, despite vacuuming regularly, can persist in out-of-the-way corners and beneath furniture.

Additional items on the carpet beetle menu include wool blankets and garments, furs (but you don't have animal hides, right?), taxidermy mounts, dry pet food, and insect collections (including my own, horror of horrors!).

Adult Anthrenus lepidus, Colorado

Getting rid of an infestation of dermestids is a real challenge. Traditional methods are of questionable effect. One of my good friends in entomology and pest control, Bill Warner, has found that moth balls, which have the active ingredient of naphthalene, are not just useless. He has observed carpet beetle larvae eating the substance. Ok, so what about moth crystals, with the active ingredient PDB (paradichlorobenzene)? At high enough concentration, that seems to work, and I have used moth crystals to protect my own insect collection. Unfortunately, PDB is potentially carcinogenic, according to the World Health Organization. The U.S. Environmental Protection Agency claims it is "not likely to be carcinogenic to humans" (National Pesticide Information Center website).

The best course of action when faced with numerous carpet beetle larvae is to discard the infested item. If you cannot bear to part with whatever is under attack, then a cycle of freezing and thawing over the course of several weeks may do the trick. This is how most museums now handle pest control in their entomology collections.

Prevention is the best cure for dermestids. Store vulnerable foodstuffs, like dried meats and dry pet food, in metal, glass, or durable plastic containers with tight-fitting lids. Store woolens, silks, and furs in a cedar chest when not in use. Cedar has proven repellent qualities and is not toxic to people or pets. Vacuum and clean your home regularly.

Adult Anthrenus sp., Massachusetts

Adult carpet beetles are pretty tiny (2-4 mm), and frequently mistaken for lady beetles since they are round, and often patterned with bands or spots of brown, black, and white. The beetles fly well and seek escape to the outdoors. Consequently, they are most often observed on windowsills, or discovered in light fixtures.

While carpet beetle larvae are pretty much "juvenile delinquents," the adult beetles can be surprisingly efficient pollinators of some flowers, especially in spring. The Buffalo Carpet Beetle, Anthrenus scrophulariae, is particularly common in flowers.

Larva of Anthrenus verbasci, © Canada Dept. of Agriculture

Carpet beetle larvae are covered in tiny hairs called setae, and these hairs can break off and become airborne, especially from the molts (shed "skins") of the larvae. These setae can cause irritation, or even trigger rhinitis or asthma in people prone to allergic reactions. Contact dermatitis is a more uncommon reaction, and an infestation has to be pretty severe to result in any kind of medical consequences (Peacock, 1993).

There are eighteen (18) species in the genus Anthrenus currently recognized in North America, and several of those are cosmopolitan pests now found worldwide as a result of international commerce. There are other common types of carpet beetles as well, with the genera Trogoderma and Attagenus being common in households. I will address those in separate blog posts.

Sources: Boone, Mike. 2013. "Genus Anthrenus - Carpet Beetles," Bugguide.net.
Gibson, Arthur and C.R. Twinn. 1931. Household Insects and Their Control. Ottawa: Department of Agriculture, Canada. 87 pp.
National Pesticide Information Center.
Peacock, Enid R. 1993. Adults and Larvae of Hide, Larder, and Carpet Beetles and Their Relatives (Coleoptera: Dermestidae) and of Derodontid Beetles (Coleoptera: Derodontidae). London: Royal Entomological Society of London. Handbooks for the Identification of British Insects, vol. 5, part 3. 84 pp.

Sunday, October 12, 2014

Spider v. Spider: A case of predation by Cesonia bilineata (Araneae: Gnaphosidae) upon spiderlings of Pisaurina mira (Araneae: Pisauridae)?

When my wife and I were traveling in Georgia, we stayed at a bed and breakfast near Madison. The inn is situated on over 88 acres of farmland, forest, and river, and teems with wildlife from birds to insects. We spent the entire day of June 14, 2014 exploring the grounds. Along one forest edge I was fortunate to find a female nursery web spider, Pisaurina mira, guarding spiderlings. She was perhaps falling down on the job, though, as another spider appeared to have free run of the nursery web, feasting on spiderlings.

A female P. mira is a formidable creature. She can measure 12.5-16.5 millimeters in body length, with an impressive sprawling legspan. Her size alone would seem to be intimidating enough. No matter, apparently, to a female ground spider, Cesonia bilineata, which was present in the nursery web among shrubbery well off the ground. Adults of this spider are half the size of the nursery web spider, female C. bilineata being a mere 4.3-7.0 millimeters from front to back, and with much shorter legs.

I did not observe the ground spider in the act of feeding on the spiderlings, but she was more plump than usual. There were living spiderlings and shed exoskeletons from spiderling molts present in the nursery web.

Cesonia bilineata might make a habit of feeding on the spiderlings of other species, as one researcher observed the species in the nursery web of a Green Lynx Spider, Peucetia viridans, in South Carolina (Willey and Adler, 1989). So far the evidence for predation on spiderlings guarded by the mother spider is apparently "circumstantial," but intriguing and highly suggestive. C. bilineata is, in fact, known to prey on other spiders by attacking the victim from behind (Bradley, 2013)

Female Pisaurina mira guarding nursery web to right of image

I also find it curious that so many of the "ground spiders" are highly arboreal, more likely to be found clambering about on foliage and twigs, or scaling walls, than to se seen scurrying over the surface of the soil. They are incredibly agile, too.

Cesonia bilineata is a common, widespread spider in the eastern United States from New England south to the Florida panhandle and west to Nebraska. Look for it in wooded habitats.

Sources: Bradley, Richard A. 2013. Common Spiders of North America. Berkeley: University of California Press. 271 pp.
Willey, Marianne B. and Peter H. Adler. 1989. "Biology of Peucetia viridans (Araneae, Oxyopidae) in South Carolina, with Special Reference to Predation and Maternal Care," J. Arachnol. 17(3): 275-284.

Friday, October 10, 2014

Flying Ants

I recently came across a male specimen of the "legionary ant" Neivamyrmex nigriscens while walking our dog in our Colorado Springs neighborhood. It was instantly recognizable to me, but it got me thinking about how most people would be hard-pressed to know what it was. Unfortunately, there are very few references for the identification of winged ants. This is a shame because it is often the "alates," males and winged queens, that are most obvious to the public.

Male Legionary Ant, Neivamyrmex nigrescens, Colorado

Indeed, worker legionary ants are mostly subterranean and nocturnal in their habits (nomadic, raid the nests of other ants to prey on the larvae and pupae), so hardly ever observed by the average person. Meanwhile, a homeowner may not notice he or she has an ant "problem" until the colony swarms, liberating a cloud of alates.

Alate queen carpenter ant, Camponotus sp., Colorado

Alates are typically larger than the worker caste of wingless, sterile females, so are more noticeable for that reason as well. In many cases, the winged reproductives resemble the workers in general appearance, but this is not always the case. The thorax of winged ants is frequently greatly expanded to accommodate the muscles that operate the wings, giving males in particular a distinctive "hump-backed" appearance.

Male carpenter ant, Camponotus sp., Massachusetts

Swarms are usually seasonal, and triggered by changes in day length, relative humidity, and air pressure, especially in the arid southwest U.S. where the onset of the monsoon rainy season sparks many ant species to swarm. These emergences can be spectacular events. Worker ants open new exits from nests in the soil, and scour the immediate vicinity to rout any potential predators and parasites.

Red Imported Fire Ant swarm, Solenopsis invicta, Georgia

Many swarm events take place in late afternoon, at dusk, after dark, or at dawn. Winged ants may be attracted to outdoor lights, which can lead to the assumption that the ants came from the house or building when that is not necessarily the case.

Colonies of a given species in a localized area swarm simultaneously such that members of different colonies can find each other and increase genetic diversity while decreasing the potential for inbreeding. Winds, and the insect's own muscle power, can take the ants far from their colony of origin.

Rough Harvester Ant swarm, Pogonomyrmex rugosus, Colorado

How do you know whether it is a winged ant or a winged termite? Please read my post on termite swarms for a concise explanation, and images of winged termites. Below is an image of a winged termite to compare to the ants illustrated here.

Alate dampwood termite, Zootermopsis laticeps, Arizona

What about wasp versus ant? That is a more problematic distinction, but most ants have distinctly "elbowed" antennae, whereas wasps often do not; or at least the first segment of the antenna is not as long as it is in ants. There are exceptions, of course, like the male Neivamyrmex ant shown at the top of this post that has no obvious elbow in the antennae.

Male Pavement Ant, Tetramorium sp., Colorado

Fortunately, I am not the only one who recognizes the need to pay more attention to alate ants in terms of research and public awareness. Laurel Hansen and Art Antonelli include a key to alates in their publication, listed below. Brendon Boudinot, in a guest post for Alex Wild's Myrmecos blog, extols the virtues of studying male ants for a clearer understanding of the phylogeny of the family Formicidae.

Alate queen thatching ant, Formica sp., Colorado

Sources: Boudinot, Brendon. 2013. "Male Ants Demystified," Myrmecos.Hansen, Laurel, and Art Antonelli. 2011. Identification and Habits of Key Ant Pests in the Pacific Northwest. A Pacific Northwest Extension Publication 624. Pullman, WA: Washington State University. 14 pp.
Houseman, Richard M. 2008. "Ants." University of Missouri Extension.