Monday, July 27, 2009

Lab Excitement

It got a little exciting in the lab today. A live, giant beetle and a dead parasite made my day much more interesting than the average Monday.

Jeff Boettner and Craig Hollingsworth showed up around lunch time with a Tuppermaid (or Rubberware, I always get those two confused) container holding a magnificent specimen of a pine sawyer. A woman brought the insect to Craig, thinking it might be a grasshopper because of the long antennae. Neither Craig nor Jeff had seen this particular species before, though it was obvious to them it was no grasshopper.

Consulting BugGuide, we eventually reached a consensus that the insect was a male “northeastern sawyer,” Monochamus notatus (Drury). Female sawyers have much shorter antennae, and shorter front legs. According to the Field Guide to Northeastern Longhorned Beetles by Douglas Yanega, this species ranges from 23-35 millimeters in body length. This one was every bit of that. Northeastern sawyers occur pretty much east of the Rocky Mountains and bore in dead and dying conifers as larvae, favoring pines. Harvested firewood can yield the beetles indoors when they emerge in stored situations. This specimen is now destined to be pinned for posterity in the University of Massachusetts insect collection. I suppose it achieves something close to immortality in this case. Hopefully more live specimens will show up, as most of my impromptu images did not turn out very well.

Another interesting find came as I was sorting leafhopper nymphs and other hemipterans preserved in alcohol from pitfall traps. One of the nymphs had some kind of dark object attached to its underside, between the first and second pairs of legs.

It turned out to be the larva of a dryinid wasp (family Dryinidae), bizarre parasites of leafhoppers and some other insects. One of the effects of ethanol on dead insects is a clearing of the pigments in some specimens, and increased magnification clearly shows the larval dryinid curled inside a capsule-like pouch.

Adult dryinids are even stranger than the larvae. Females are often wingless, and sport scissor-like front feet used for gripping the leafhopper while an egg is laid on it. The adult wasps have also been observed catching, killing, and half-consuming prey instead of using it as a host for their offspring. For more images of both larvae and adults, please see the BugGuide reference page and Alex Wild’s fantastic images of an adult female.

Hm-m-m-m, I wonder what tomorrow will bring?

Friday, July 24, 2009

House Centipedes

One of the most confounding, and arguably creepiest, creatures I am asked about at has to be the “house centipede,” Scutigera coleoptrata. Neither insect nor arachnid, it is variously described to me as spidery, an animated feather, a speeding, ghostly apparition, and plenty of other epithets born out of both fear and fascination.

This species seems to be genuinely domestic, occurring mostly in and around human habitations where these venomous predators prowl in search of other invertebrates to eat. It is thought to have originated in the Mediterranean region, but unless one starts speaking Italian or Greek, you could fool me. International commerce has now succeeded in transporting the house centipede to virtually all inhabited corners of the globe anyway.

Related species in the genus often live in caves, and indeed the long legs and antennae of this animal are characteristic of habitats where visual acuity is much less important than a sense of touch. The lanky build of these creatures also makes them appear much larger than the 25-35 mm body length of the average specimen. Couple that with the incredible speed at which they can travel, and you have the heebie-jeebies come to life. I confess they can even freak me out at times because they can climb walls and scurry across ceilings at about Mach 7.

Fortunately, house centipedes are totally harmless to people and pets (well, if you have a flea circus I guess you’d better be careful). I encourage folks who encounter house centipedes to just let them continue their pest control patrol, like this one is doing, or usher the centipede into a container and release it outdoors in a woodpile, rock wall, or other sheltered situation where it will be equally happy hunting for food and mates. Those approaches are certainly preferable to "Honey, can you get me a shoe? A really big shoe?"

Wednesday, July 15, 2009

Firefly Tag

There is something about fireflies that is undeniably enchanting, and I looked forward to seeing them here in western Massachusetts. They occur in Arizona, too, albeit different species restricted mostly to riparian (streamside) habitats. Back on the evening of June 17, I looked for fireflies and other insects around the schoolyard here in South Deerfield. I was not disappointed.

The fireflies I came to know from my days in Cincinnati, Ohio, are largely crepuscular species, most active at dusk. Here, they appear to be active only after dark. Still, they ready themselves in the waning hours of daylight, appearing more out in the open on foliage along the edges of forests and fields.

The first firefly I encountered was a species of Photuris. It has been recently discovered that there are several cryptic species which can only be identified from subtle differences in their flash patterns. Morphologically, and apparently even genetically, they are otherwise identical.

Photuris gained infamy decades earlier when it was revealed that the females of one species, P. pennsylvanica, habitually mimic the flashes of female Photinus pyralis, thereby attracting the males of that other species. The male Photinus, no doubt optimistic at a positive response from a potential mate, alights to find the large female Photuris to be in the mood for something else. She devours him. Literally.

Dr. Thomas Eisner of Cornell University was the gentleman and scholar who not only discovered this behavior, but learned why it occurs. The father of chemical ecology, Dr. Eisner deduced that Photinus fireflies produce potent defensive chemicals called lucibufagins. That’s correct, the compounds are steroidal pyrones related to toad toxins. The Photuris fireflies, however, do not produce this chemical, instead acquiring it through the consumption of their cousins.

Ironically, the next firefly I found was a male Photinus. It is not pyralis, but a different species I have yet to identify. Just beginning to stir, he made a patient photographer’s model.

As darkness began to descend, along with hordes of hungry mosquitoes that made continued searching unpleasant, if not nearly intolerable, I managed to spy a female Photinus, perched on a grassblade. I would need my camera’s pop-up flash to illuminate her, but what I didn’t expect was her reaction to it.

After my flash would go off, which must have seemed like the sun exploding to the poor girl, she would twist her body and return the flash, though infinitely dimmer. Now it was obvious that she thought I was the male firefly of her dreams. Any male capable of producing that bright a light must be the most genetically fit of all her kind. I found it fascinating that she would purposefully direct her flash as well. There was no question where she was aiming it.

Try as I might, I could never catch her own signal. My flash simply failed to recharge in time to capture her faint greenish glow. It was a miracle I could even catch the literal tail-end of her contortionist performance with a subsequent shot.

I was recently asked if only the male fireflies fly and flash, and it appears to be true of at least a few species. It pays females to keep a low profile in grass or foliage, since they invest heavily in the production of offspring. Males are more “expendable” in the genetic sense, though anyone who has tried to catch flying fireflies knows just how futile an exercise it can be.

I enjoyed my game of “firefly tag” with the lovely female Photinus, but fearing she may not have enough battery life to reply to real males, I eventually let her be. Please share your own firefly encounters, and watch this space for future posts on fireflies, and the book about them that I have brewing….

Tuesday, July 7, 2009

Another day in Entomology Land

Once I finished sorting the pitfall trap samples by order (beetles separate from flies, wasps, spiders, etc), then I set about trying to identify the Hymenoptera (ants, wasps, bees) more specifically. Mind you, I am used to dealing with insects over five millimeters long. In the world of pitfall traps, anything that big is absolutely gigantic. Most of what I’m coming across are minute parasitic wasps and a few ants. The following is a typical sort from order to family level or below in terms of classification.

I start by dumping the vial into a watchglass. The specimens usually stick to the vial, so I have to wash them out with alcohol. Some are very stubborn indeed. Then I stick the watchglass under the microscope and start sorting. A sample may contain anywhere from one to twenty or so specimens, hopefully all of them belonging to the same order (Hymenoptera in this case).

I segregate them by the most specific classification I am able. This often requires the use of scientific documents called “dichotomous keys.” A key is a series of couplets, each couplet describing one or more characters of external anatomy of the insect before you. You find the character(s) that match your specimen, then proceed to the next couplet and so on, until you arrive at a family, genus, or species name. If I am keying out an insect from Massachusetts, and I arrive at a family of insects found only in Sumatra, well, guess who made a boo-boo? This can be no fault of your own, though. I once keyed out a wasp to a genus found only in Japan because my specimen was missing one tarsal (foot) spine that had broken off. Sure enough, the other leg had the full complement of spines. Yes, it is enough to drive you crazy.

The microscope I am using is a binocular stereo “zoom” model that, near as I can tell, takes me up to fifty power (fifty times the size of the insect you are viewing). Even this is not always enough. I had to laugh when I came across one couplet in a key that was illustrated with an SEM! Sure, I’ll jut bop on over to my neighborhood scanning electron microscope, no problem. The University of Massachusetts does have one, but you can’t just barge in with your bug. It is a major exercise to render images of anything under one of those machines, including coating the specimen in a thin layer of gold.

Fortunately, my friend Jeff Boettner was able to rustle-up another key that is much more user-friendly. Got to credit Agriculture Canada for producing such fine works, eh?

Now, if it were only still in print….

It is very gratifying to find that your specimen matches the illustrations in the key, like the sculpturing on the propodeum (hindmost part of the thorax) of this cynipid gall wasp (figure "aa" on the page of the book shown here). Yes, the specimen is standing on its head in this imge.

I am truly learning as much doing this work as I am producing for the university, but then, isn’t that what life should be about? Soon I will share more images of some of the spectacular little insects I’m finding in these samples.