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'sThatBug.com

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 Bugguide.net 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.

"Daniel:

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:

Bugguide.net

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.

Eric"

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.

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.

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," EuroSpiders.com
"Zygiella x-notata," NatureSpot.org.uk
"Summary for Zygiella x-notata (Araneae)," British Arachnological Society.

Underside of spider

Sand Wasps, Genus Bembix

Solitary wasps are among the most easily observed of insects, and their behaviors and life histories are intensely captivating. Sand wasps in the genus Bembix are familiar and common throughout North America, digging their burrows in dunes, on beaches, and other habitats with loose, deep sand.

Bembix female, New Jersey

I had the good fortune of witnessing an industrious female sand wasp excavating her nest at Lathrop State Park in Huerfano County, Colorado last August 4, 2014. Insect activity was minimal in the late afternoon as the wind was picking up a bit and a thunderstorm was quickly approaching. While my wife was looking for a geocache, I studied the nearby vicinity and noticed a hole in the sand. Before I could complete the thought of "Hm-m-m, I wonder what dug that?," a sand wasp backed out of the cavity.

Bembix female, Lathrop State Park, Colorado

The industriousness of a Bembix female is something to behold, as you can see in the video below. She rapidly kicks out large quantities of sand using a "tarsal rake" of spines on each front leg.

There are twenty-one species of Bembix in North America north of Mexico, so generalizations about their behavior are risky. Still, the burrows are oblique, nearly horizontal in many cases, ranging from 19-57 centimeters in length, and a depth of 5-28 centimeters. The tunnels may curve, and usually end in a terminal cell. Several species also dig short, dead-end burrows or furrows in the immediate vicinity, probably to confuse parasites. The entrance of the real, finished burrow is thoroughly concealed.

The burrow is excavated before the wasp goes hunting. True flies in the order Diptera, exclusive of the suborder Nematocera, are used as prey. Bembix are generalist, opportunistic hunters. A victim is paralyzed or killed by the wasp's sting, and is then flown back to the nest. She uses subtle landmarks to unerringly find the buried entrance. Meanwhile, we can't remember where we parked our car. Most of our common Bembix species will lay an egg on this first victim, but some species lay an egg in the empty cell before commencing the hunt.

Once the egg hatches, the mother wasp brings flies to her larva as needed. This is called "progressive provisioning" and is more typical of parental care in birds or mammals than in insects. When the larva reaches maturity, the female wasp closes the cell. Inside, the larva spins an oblong cocoon, weaving sand grains into the structure and resulting in a hardened capsule. Overwintering takes place as a prepupa inside this cocoon, but there are usually two generations annually.

The mother sand wasp may fill in her burrow once her single larva reaches maturity, or she may construct one or two additional cells, each at the end of a short tunnel branching from the main burrow.

Bembix male, southern California

Male sand wasps are often seen alighting on the ground amid the numerous burrows of females, but they also participate in elaborate flight rituals called "sun dances." Males emerge before females, and fly at erratically at dizzying speed one or two inches above the ground attempting to detect virgin females about to erupt from their underground chambers.

Females join the males in flight if they are not pounced on immediately, and a pair that unites in mid-air will make a bee-line out of the mob and finish mating elsewhere before re-joining the masses. Should a pair tumble to the earth, great numbers of males will try and usurp the initial suitor.

Bembix female on saltcedar flowers, Colorado

Both sexes fuel their frenetic lifestyle with flower nectar, especially from composites (flowers in the aster family). Some of their mouthparts are fused into a tongue-like proboscis they use to probe for nectar. Sand wasps do nothing slowly it would appear, and one barely gets a glimpse of them, even at a flower, before the wasp is off to another destination.

Bembix wasps are plagued by the usual suspects that parasitize wasp nests: Cuckoo wasps (Chrysididae), velvet ants (wasps in the family Mutillidae), satellite flies (Sarcophagidae), and bee flies (Bombyliidae) being the chief villains in the sand wasp world. Additionally, the adult wasps can be victimized by parasitic thick-headed flies (Conopidae), or killed outright by robber flies (Asilidae).

Watching a nesting aggregation of sand wasps is never a disappointment, and at the very least you will find joy in each and every pesky fly they dispatch in providing for their larval offspring.

Bembix in Colorado

Sources: Bohart, R.M. and A.S. Menke. 1976. Sphecid Wasps of the World. Berkeley: University of California Press. 695 pp.
Evans, Howard E. 1966. The Comparative Ethology and Evolution of the Sand Wasps. Cambridge, MA: Harvard University Press. 326 pp.
Rau, Phil and Nellie. 1918. Wasp Studies Afield. Princeton, NJ: Princeton University Press. 372 pp. (Dover edition, 1970).