Thursday, February 26, 2015

Green-eyed Wasps, Tachytes

Identifying wasps in the field is often problematic for a number of reasons. Wasps move quickly, and often you only get a glimpse. Mimicry complicates matters and you may actually be looking at a fly, moth, beetle, or true bug. "Field marks" are seldom visible, at least without a magnifying lens. One exception is the genus Tachytes, in the family Crabronidae. The larger species in the genus often have huge green eyes.

Tachytes from South Deerfield, Massachusetts

These insects have been referred to as "sand-loving wasps" in some literature, but they nest in a variety of soil types. I think they deserve the name "green-eyed wasps" because that character is more vivid, even if it does not apply to every species. Males in particular have very large eyes, the better to detect passing females or rival males while scanning the landscape from their perch on a stone, leaf, flower, or twig.

Male Tachytes defending territory from perch in Colorado

Interestingly, one of the hallmarks of the Larrini tribe within the Crabronidae is the reduction of their "simple eyes" (ocelli) to the point of being mere "scars." In Tachytes, the ocellar scars are shaped like golf clubs, having long "tails" running part way down the head. The image below shows the scars between the compound eyes, at the point where they begin to diverge from one another.

Close-up of Tachytes from Colorado

The female wasps excavate burrows in the ground, the tunnels ranging from 7 centimeters to nearly one meter in length, and to a depth of 7.5 to 70 centimeters. Several individual cells are arranged along the length of the burrow, or at the end of tunnels that branch from the main shaft. Some species dig their nests just inside the entrances of burrows made by other organisms such as rodents, lizards, or cicada killer wasps; and at least one species works at night.

All North American species provision those cells with immature grasshoppers (Acrididae), pygmy grasshoppers (Tetrigidae), katydid nymphs (Tettigoniidae), or pygmy mole "crickets" (Tridactylidae). The female wasp paralyzes the victim with her sting, then straddles it, grasps it by the antennae with her jaws, and flies it back to her nest. There, she deposits her prize in one of the cells. One to thirteen victims are placed in each cell, and an egg is laid on the last one.

Male Tachytes atop female in Colorado

Males employ two strategies to find mates. They emerge before females, so at first they defend small territories in the vicinity of areas where females are likely to emerge. Later in the season they defend territories around nesting sites. I have observed them defending territories around nectar resources, too, namely a solitary blooming saltcedar tree (Tamarix sp.) in a large expanse of degraded shortgrass prairie here in Colorado Springs.

The male pounces on the back of a female, pinning her wings to her body, and then beginning courtship behavior. Apparently this amounts primarily to waving his antennae frantically over the female's face, as shown in the short video below. This behavior may not hold true for all Tachytes species, and certainly the duration of courtship and copulation can vary dramatically.

Should the female be receptive, mating ensues. The image below clearly shows a male deploying"junk" in preparation for mating. Ok, the technical term is "aedeagus," composed of two "penis valves," and it is the blunt, central structure protruding from the tip of the abdomen in the image. The longer, more slender appendages framing the aedeagus are the "gonostyles." The "volsella" is a shorter spur at the base of each gonostyle. Insect genitalia are complex organs designed to work as a female "lock" and male "key" to prevent cross-breeding with similar species. Indeed, dissection of the male genitalia is often required for species identification in many insects.

Tachytes pair from Colorado

There are 35 species of Tachytes in North America north of Mexico. They are among our more common solitary wasps, easily observed as they feed on flower nectar, though they flit rapidly from blossom to blossom. Males also land on foliage, stones, or the ground, usually returning repeatedly to the same perch or one very close by. This represents the territorial defense behavior, and it allows for great photographic opportunities provided you don't make sudden movements. Happy wasp watching.

Sources: Bohart, Richard M. 1994. "A Key to the Genus Tachytes in America North of Mexico with Descriptions of Three New Species (Hymenoptera, Sphecidae, Larrinae)," Proc. Entomol. Soc. Wash. 96(2): 342-349.
Bohart, R.M. and A.S. Menke. 1976. Sphecid Wasps of the World. Berkeley: University of California Press. 695 pp.
Krombein, Karl V. and Paul D. Hurd, Jr. 1979. Catalog of Hymenoptera in America North of Mexico Vol. 2 Apocrita (Aculeata). Washington, DC: Smithsonian Institution Press. pp. 1199-2209.
Kurczewski, Frank E. and Margery G. Spofford. 1986. "Observations on the Nesting Behaviors of Tachytes parvus Fox and T. obductus Fox (Hymenoptera: Sphecidae)," Proc. Entomol. Soc. Wash. 88(1): 13-24.
Kurczewski, Frank E. and Edmund J. Kurczewski. 1984. "Mating and Nesting Behavior of Tachytes intermedius (Viereck) (Hymenoptera: Sphecidae)," Proc. Entomol. Soc. Wash. 86(1): 176-184.
Kurczewski, Frank E. and Edmund J. Kurczewski. 1971. "Host Records for Some Species of Tachytes and Other Larrinae," J. Kansas Entomol. Soc.. 44(1): 131-136.
Kurczewski, Frank E. 1966. "Behavioral Notes on Two Species of Tachytes That Hunt Pygmy Mole Crickets (Hymenoptera: Sphecidae, Larrrinae)," J. Kansas Entomol. Soc. 39(1): 147-155.
O'Neill, Kevin M. 2001. Solitary Wasps: Behavior and Natural History. Ithaca: Comstock Publishing Associates (Cornell University Press). 406 pp.

Sunday, February 22, 2015

Bridge Orbweaver (Gray Cross Spider)

Downtown Portland, Oregon features a promenade on both sides of the Willamette River, and it is a stroll, bike ride, or jog worth taking simply for the scenery and people-watching. Should you be interested in spiders, it is even more worthwhile. Many manmade structures are occupied on the exterior by the Bridge Orbweaver, Larinioides sericatus. Even in December and early January of this year, specimens of varying ages were abundant.

This species is also known as the "Gray Cross Spider," and it is easily confused with the very similar Larinoides patagiatus, which has no common name. Further complicating matters, the Bridge Orbweaver has been going by the Latin name L. sclopetarius until very recently. A revision of the genus Larinioides was published in the journal Zootaxa about two months ago (see citation below).

These are fairly large spiders, mature females measuring 8-14 millimeters in body length, and males 6-8 millimeters. Their legspan makes them appear even larger to the untrained eye. Both genders share the same distinctive pattern on the carapace (top of cephalothorax) and abdomen. The overall color is generally gray, but some specimens tend toward brown.

Mature male from Massachusetts

The spider normally hides in a retreat on the periphery of its circular web during the day, and emerges to repair or reconstruct the snare at night. The spider then spends the night in the hub of the web, hanging head down. The spiders can also be there in the center of the web on overcast days, and juvenile specimens tend to be more likely to occupy the hub during the day than mature individuals.

Female making a kill in Massachusetts

While this species is particularly common close to water, where emerging aquatic insects like midges and mayflies are an abundant food source, I have also seen the Bridge Orbweaver in other settings in western Massachusetts. It can be a fixture around outdoor lights, where insect prey is drawn in great numbers. Spiders are quick to take advantage of resources like that, and competition for prime "web sites" is keen.

Underside of adult female, Oregon

Larinioides sericatus is found not only in the U.S. and Canada, but Europe as well. It is strongly suspected that it was even introduced to North America from the Old World. Records from Asia are now attributed to yet another species, L. jalimovi. Here, the Bridge Orbweaver is known from the maritime provinces, Quebec, Ontario, Alberta, and British Columbia south to Minnesota, Wisconsin, Illinois, Indiana, Ohio, New England, Virginia, Kentucky, Washington, and northwest Oregon. Isolated records exist for extreme northeast North Carolina, Oklahoma, and northwest Utah, at least some of which probably need confirmation. Recent voucher specimens have been taken in Long Beach, California.

Special thanks to Ivan Magalhäes and Laura Lee Paxson on the Facebook page for the American Arachnological Society for setting me straight as to the proper scientific name for this species.

Sources: Bradley, Richard A. 2013. Common Spiders of North America. Berkeley: University of California Press. 271 pp.
Dondale, C. D., Redner, J. H., Paquin, P. & Levi, H. W. (2003). The insects and arachnids of Canada. Part 23. The orb-weaving spiders of Canada and Alaska (Araneae: Uloboridae, Tetragnathidae, Araneidae, Theridiosomatidae). NRC Research Press, Ottawa, 371 pp.
Hollenbeck, Jeff, et al. 2013. "Species Larinioides sclopetarius - Gray Cross Spider,"
Šestáková, Anna, Yuri M. Marusik, and Mikhail M. Omelko. 2014. "A revision of the Holarctic genus Larinioides Caporiacco, 1934 (Araneae: Araneidae)," Zootaxa 3894(1): 061-082.

Friday, February 20, 2015

Insidious Insect Fungi

The Walking Dead is a popular television show these days, but reality is perhaps even more sinister. Did you know that there are fungi that hijack the brains of insects causing them to behave in ways that benefit the fungus? It's true, and you have probably seen evidence of this macabre life cycle without knowing the answer to the mystery.

Fly infected with fungus attached to a leaf (Massachusetts)

Cheryl Harner, a naturalist and writer at Weedpicker's Journal, asked me about this bizarre phenomenon a couple of years ago, and I always meant to learn more about it myself. You owe it to yourself to check out her blog, and I'll try to complement her post rather than compete with it. She did an excellent job of researching and linking, though.

Dead grasshopper nymph that has climbed a grass stem due to funal infection (Massachusetts)

It is not just grasshoppers and ants that are victimized by what are called "entomopathic" fungi. Flies are among the most conspicuous of hosts. You have probably seen flies clinging to foliage or twigs in odd, contorted positions, with bloated abdomens. The spores of the Entomophthora muscae fungus have their hosts literally bursting at the seams, the membranes between the abdominal segments.

Meanwhile, grasshoppers and related orthopterans are plagued by Entomognatha grylli, and lady beetles are often afflicted with Laboulbeniales fungi.

The life cycle of fungi in the order Entomophthorales begins when a spore lands upon an insect. However, many of the fungi are very host-specific, so if a spore lands on the "wrong" bug it is likely done for. Should the spore contact the correct host, it soon germinates, penetrating the cuticle of the insect and growing internally, absorbing the host's nutrients, eventually killing it. Before the doomed creature perishes, the fungus does something remarkable. In many cases it stimulates the host to seek a high point, either by climbing or flying, whether or not the insect normally performs such behavior. This phenomenon is sometimes referred to as "summit disease."

Headless grasshopper corpse in wake of fungal infection (Colorado)

Once the host insect ascends a grass stem, for example, the fungus sends out special structures called rhizoids that are white, thread-like filaments. These fibers often emerge from the insect's tarsi ("feet") or mouthparts, anchoring the bug to the substrate such that it is not easily dislodged after death. Now the spores erupt, sometimes in the form of fruiting bodies like other fungi, or simply exuding from holes in the host's cuticle.

Carolina Leafroller ("cricket") showing fungal rhizoids penetrating its feet and anchoring it to the leaf (Ohio)

Grasshoppers are among the most conspicuous victims if only because of their size, but most types of insects, and spiders, too, are vulnerable to fungal infection. The typical appearance of fungus victims are stiff, dessicated specimens that are essentially mummified.

Harmonia axyridis with perithecia of Hesperomyces virescens at the tip of its wingcovers (elytra)

Fungi in the order Laboulbeniales affect beetles in particular, and are very different in their mode of dispersal and effect on the host. Hesperomyces virescens apparently afflicts only the Multicolored Asian Lady Beetle, Harmonia axyridis, at least here in North America. It is microscopic, and is essentially a sexually transmitted disease since the overwhelming means of infection occurs during mating of the host. Spores can also transfer when large groups of overwintering lady beetles force the insects to rub against each other.

Mating pair of Harmonia axyridis in Illinois exhibiting symtoms of Hesperomyces virescens

Most adult beetles exhibit symptoms in the form of tiny, yellow, scale- or flake-like protrusions from the cuticle, especially at the tip of an elytron (wing cover). These are the fruiting bodies, called perithecia, from which spores are issued, if I comprehend the literature and language of mycology correctly. Interestingly, the fungus has little or no effect on the host, but depends on it for reproduction.

When one thinks of mortality factors that affect insects, or most other animals, we tend to forget the impact of fungal organisms. Maybe I have seen one too many episodes of the television show Monsters Inside Me, but I have a whole new respect for fungi now. It helps to remember that fungi are often very host-specific, so handling a fungus-ridden bug is not going to pose a health threat to a human. As far as we know.

Fungus-infected fly corpse on leaf (Colorado)

Sources: Eiseman, Charley and Noah Charney. 2010. Tracks & Signs of Insects and other Invertebrates. Mechanicsburg, Pennsylvania: Stackpole Books. 582 pp.
Parker, Abigail M., et al. 2010. "with Labioulbeniales fungus,"

Monday, February 16, 2015

From My Inbox

Once the general public gets wind of your expertise in entomology, you are invariably inundated with requests for identifications of specimens, images, even fuzzy recollections that are then related to you. The digital age has made entomologists and naturalists much more accessible, and I believe that is a very good thing. Exterminators have always been accessible. It is also a good thing for those of us answering inquiries because it often presents a challenge, or a window to species from faraway lands, or in some cases represents a new or potentially invasive species.

Semanotus amethystinus (Amethyst Cedar Borer) from "Sara S." in Portland, Oregon via What'

One of my regular "clients" is the webmaster for What's That Bug?, a very popular website that receives submissions from all over the globe. Daniel Marlos, who runs the site, started it on a relative lark as an example of pop culture. He quickly found he was filling a huge void, but had little knowledge of entomology himself. Over the years that has changed dramatically, and Daniel can now identify most common critters. He is better at identifying Australian insects and arachnids than I am. Still, he gets stumped every once in awhile, and will e-mail me for help.

Much of the time, I am clueless, too, but I enjoy the investigative work of coming up with an answer if I can. Take this submission from "Sweetpea" in Montreal, Quebec, Canada, for example. I did not recognize this longhorned beetle and thought it might be something exotic that found its way there in the fashion of the notorious Asian Longhorned Beetle. A quick search of proved it was actually the native "Linden Borer," Saperda vestita. I learned something in the process of helping.

Here's another example. My response to Daniel is under the images.


We were both wrong! You thought it was a clerid or a tenebrionid. I thought for certain it was a spider beetle (Anobiidae: Ptininae or Ptinidae). Turns out it is a longhorn! Here:

Crazy. I knew it looked familiar, but it took looking in an old, dusty copy of Essig’s Insects and Mites of Western North America to find a figure that matched.

Would love to share these images on Bugguide and maybe in a blog post. Thanks.


Sometimes I even get forwarded e-mails as the chain of included experts expands even longer. One of my friends in Arizona sent me the image below that depicts an ovipositing female bee fly at the Gilbert Water Ranch near Phoenix, Arizona.

© Laurie Nessel

I am increasingly impressed and delighted by how observant and curious many people are about the invertebrate world.

Occasionally, friends will simply share images they think I would enjoy, like this male Anise Swallowtail photographed by David M. Elwonger on the summit of Signal Butte in the Pike National Forest here in Colorado. I had not been aware that the species occurred east of the Rockies prior to his e-mail to me.

© David M. Elwonger

Please, keep the proverbial cards and letters coming, there is no such thing as a stupid question or unimportant observation. At the very least, if it is important to you, then it is important to me, too.

Saturday, February 14, 2015

New Feature: Blog Categories

Better late than never I have finally gotten around to grouping some of my posts by category, using the "Link Lists" gadget that Blogger offers in the "layout" part of "design." The category list is located at the top of the right hand sidebar.

Now you can find all the "Wasp Wednesday," "Spider Sunday," and most of the "OrThoptera Thursday" posts conveniently, without having to scroll through all 500+ posts. Additionally, I offer categories for commonly-encountered indoor insects and biting "bugs" for the casual visitor who may want to try and quickly identify something they found at the home or workplace.

I hope you find this new feature useful, and I welcome suggestions for additional categories. My other post topics seem diverse enough that any other categories would, at this time, be relatively minor, though. I aim to be responsive to my readers, but I get precious little feedback. That either means I am delivering useful material, or no one cares one way or the other. Ha! I am hoping it means the former.

Sunday, February 1, 2015

Missing Sector Orbweaver, Zygiella x-notata

During my stay in Oregon during December and the first week of January, I was surprised to see how many spiders were still active in the relative cold and damp. The most conspicuous of those arachnids were the Missing Sector Orbweavers, Zygiella x-notata, which seemed to occupy the corner of every window frame, outdoor light, or other manmade structure.

This species is easy to identify, simply from the web alone. It looks as if the spider forgot to finish it. A substantial wedge of the sticky spiral is missing from the top half of the web, the central radius in the sector running to a tubular retreat on the periphery where the spider usually resides. The web spans anywhere between 6-14 centimeters in diameter.

Zygiella web, spider in upper right corner

The spiders will come out to sit in the hub (center) of the snare at night, or even on overcast days; and young spiders are more apt to station themselves at the center than older spiders. Adult females measure 7.4-8.7 millimeters in body length, males 6-6.5 millimeters. The color and pattern is pretty consistent across all specimens, as shown in the images here.

Male specimen

Zygiella x-notata is not native to North America, having been introduced here from Europe who knows how long ago. It is well-established here now, from the California coast through western Oregon and Washington, and also along the Atlantic coast, from New England to Virginia. Another adventive species, Z. atrica, is known from northwestern Washington and southern British Columbia. Z. nearctica is boreal, occurring coast to coast in Canada, plus Alaska, New England, the Rocky Mountains to Colorado, and the Appalachians to North Carolina.

Two native species formerly placed in Zygiella have been reclassified into the genus Parazygiella: P. carpenteri with a disjunct occurrence in the Sierra Nevada mountains, California coast, and also southeastern Washington; and P. dispar from southern British Columbia to the vicinity of Monterey, California (though this is a holarctic species also found in Europe). P. carpenteri usually spins a complete orb web.

Spider in tubular retreat with egg sac

Back to Z. x-notata. It is also known under the aliases of "Winter Spider," "Opensector Orbweaver," and "Silver-sided Sector Spider." I recall this species being most abundant along the waterfront of the Columbia River when I was a child, but it is now among the most abundant of spiders even up in the hills of southwest Portland. It certainly associates itself with buildings, bridges, docks, and other structures.

What would these spiders feed on during the winter months? Many moth species fly throughout the colder months in the Pacific Northwest, plus winter crane flies, other dipterans, and some beetles. Orbweavers often crowd their snares around outdoor lights to further improve their odds of catching a meal.

Female with egg sac

Keep exploring during the winter months, even if it is only around the exterior of your home, office, or other building. You might well encounter one of these spiders, or any number of other organisms.

Sources: Adams, R.J. 2014. Field Guide to the Spiders of California and the Pacific Coast States. Berkeley: University of California Press. 303 pp.
Bradley, Richard A. 2013. Common Spiders of North America. Berkeley: University of California Press. 271 pp.
Sollfors, Stephan. 2010. "Zygiella x-notata,"
"Zygiella x-notata,"
"Summary for Zygiella x-notata (Araneae)," British Arachnological Society.

Underside of spider