Another Rarity: Nysa Roadside-Skipper in Colorado

This is what you get for exploring, observing, recording, and being curious: Surprises. I am not well-versed in things butterfly, but I do know when I haven't seen a particular species before. Even if I cannot say anything about a creature in the field, I can go and research it later. Such was the case of the Nysa Roadside-Skipper encountered on Monday, May 15, in Lamar, Prowers County, Colorado.

It always starts innocently enough, and sometimes results from disappointment over something else. I would much rather find interesting wasps, beetles, grasshoppers, and true bugs instead of butterflies, but it so happened that recent bad weather (a cold snap a couple weeks ago and heavy rains more recently) left little to find besides Lepidoptera in Lamar. Some Lepidopterist out there is going to make me envious by finding a cool wasp now.

So, my wife, Heidi, and our mutual friend Jill White Smith, took the field looking for birds and whatever other wildlife we could see. Jill is a very accomplished photographer. You can see her work at Nature Made Photography on Facebook, in fact. She does "people photography," too, as she puts it. She is also very generous and welcoming, and eagerly showed us around to her favorite haunts.

One of those habitats is an abandoned, unpaved road that is quickly becoming part of a dune or sandhill adjacent to the riparian corridor of Willow Creek, south of the Lamar Community College campus. Flies, damselflies, a few bees, and butterflies flew up every few steps. I happened to notice one small one land in the road, and I focused my camera. I could tell it was a skipper, but not one I had ever seen before. I had left my field guides at home, but that only served to build suspense.

We got home from the three-plus hour drive around eleven at night. After unloading the car, I consulted my Kaufman Field Guide to Butterflies of North America. Thanks to Jim Brock and Kenn Kaufman, I quickly found my mystery skipper: the Nysa Roadside-skipper, Amblyscirtes nysa. The only "problem" was that the range map for the species does not include Colorado. Heidi did a bit more research and found only one Colorado record online at Butterflies and Moths of North America (BAMONA), and no Colorado records on Bugguide.net. I consulted an old book, Butterflies and Moths of the Rocky Mountain States, and found no historical records for Colorado.

What do we know about this insect? Its known range is from Mexico, southeast Arizona, southern New Mexico, and the western two-thirds of Texas north and east through Oklahoma and the eastern two-thirds of Kansas, barely crossing into Missouri. There are between one and three generations ("broods") each year, depending on the geographic location of a given population. The caterpillars feed on grasses. The Kaufman guide adds: "Males perch in wash bottoms, road depressions, or along trails very early n the morning before retiring to shade for the afternoon." This guy was overdue for a nap, then, at almost 10:00 AM.

We also saw what I thought was a small Common Sootywing, but it turns out what I saw was the dorsal (top) view of this same skipper. I narrowly missed an opportunity to get a shot, but here is one of a specimen in Arizona:

© Philip Kline via Bugguide.net

Lastly, while taking images of the skipper, I noticed what might be the cutest beetle ever. I had to bring it home to get images. As near as I can tell, it is a darkling beetle in the genus Edrotes, for which there are also no Bugguide records for Colorado.

Discoveries like these await you, too. You do not have to know what you are looking at to enjoy the moment, capture it in pixels or digital video, and share it with others. You explore and observe often enough and long enough, and you are almost guaranteed to find something truly unusual, or even unknown.

Sources: Brock, Jim P. and Kenn Kaufman. 2003. Kaufman Field Guide to Butterflies of North America. Boston: Houghton Mifflin Co. 384 pp.
Ferris, Clifford D. and F. Martin Brown. 1981. Butterflies of the Rocky Mountain States. Norman: University of Oklahoma Press. 442 pp.

ID Tip: Ground Beetle or Darkling Beetle?

I have decided to begin a new, recurring feature here called "ID Tips" that will be designed to help naturalists, amateur and student entomologists, and others solve common and basic problems in insect and spider identification. Our first installment will explain differences between ground beetles (family Carabidae) and darkling beetles (family Tenebrionidae). The two are easily confused, but generally straightforward once you know what to look for.

Ground beetle, Dicaelus sp.; note antennae, exposed jaws

Darkling beetle, Embaphion sp.; note antennae, hidden jaws

Physical Features

One glaring difference between carabids and tenebrionids is the structure of the antennae. In ground beetles, the segments of the antennae are usually longer than wide, giving the antenna the appearance of a near single filament. Darkling beetles have mostly bead-like segments, such that the antenna resembles one of those keychains that closes by pushing the filament between the beads into a clasp. This is not a foolproof character, but works enough of the time that it will help you make a quick determination.

Ground beetle, Calosoma sp.; note antennae, exposed jaws

Darkling beetle, Eleodes sp.; note antennae, concealed jaws

Look also at the front of the head. Are the mandibles (jaws) exposed and directed forward? If so, then you have a ground beetle or another kind of predatory beetle. Conversely, if the mandibles are concealed beneath the clypeus ("upper lip" if you will), then it is likely your specimen is a darkling beetle or another beetle that feeds on vegetation or detritus.

Behavior

Does your beetle move very rapidly by running? This is another characteristic of ground beetles. Many species are so fast that it is a real challenge to catch them for closer examination. Does your beetle lumber along slowly or only run fast when prodded? Chances are you have a darkling beetle then. Many darkling beetles rely on a very dense exoskeleton to repel attacks by predators, and consequently don't feel the need to flee in haste. Desert and prairie species may even have the wing covers fused to help limit water loss.

Ground beetle, Chlaenius sp., that has a stink defense

Does your beetle stand on its head when disturbed? This head-standing behavior is characteristic of the darkling beetle genus Eleodes, and some other closely-related genera. Both darkling beetles and ground beetles can have extremely effective chemical defenses that include pungent, permeating aromatic compounds released from abdominal glands, so smelling your beetle to make an identification is not only a potential exercise in futility, it can be highly unpleasant if not injury-inducing.

Darkling beetle, Helops pernitens, with antennae like a ground beetle (but concealed jaws)

Habitat

Habitat is not a good way to distinguish ground beetles from darkling beetles. Both can be found in a variety of habitats, and are especially abundant and diverse in aridland ecosystems.

Complicating Factors

Because both carabids and tenebrionids are well-defended insects, they are mimicked by a variety of unrelated insects. One prime example is the longhorned beetle genus Moneilema, which mimics Eleodes darkling beetles not only in appearance, but behavior. The longhorned beetles, which feed mostly at night, on cactus pads, move slowly and even stand on their heads like Eleodes. They have no chemical defense to back-up their warning posture, but the bluff works fine on all but the most desperate of insectivores.

Darkling beetle (Eleodes sp.) head-standing

Cactus longhorned beetle (Moneilema sp.) mimicking Eleodes spp.

Another complication is the relatively recent assimilation of two former beetle families into the Tenebrionidae, many of which do not resemble "classic" darkling beetles. These are the comb-clawed beetles (subfamily Alleculinae) and long-jointed beetles (Lagriinae).

Comb-clawed beetle, Hymenorus sp., a type of darkling beetle

Long-jointed beetle, Statira sp., an aberrant darkling beetle

In contrast, the "ironclad beetles" in the family Zopheridae were once members of the Tenebrionidae. They include beetles so well-armored that entomologists have extreme difficulty in pinning specimens that they collect.

Ironclad beetle, Zopherus tristis

No single character is probably reliable by itself, and it is recommended that one use a dichotomous key, in a technical book or online, to reach a firm conclusion on the identity of your beetle. It is also a great idea to invest in a good dissecting (binocular) microscope. Good luck!

Big Black Beetles: Coelocnemis

Darkling beetles in the family Tenebrionidae are deceptively confusing. They are so diverse that when I am confronted by an unusual beetle I generally start by ruling out tenebrionids. Within the family itself, many genera are very similar in appearance. Most armchair entomologists think that all the big black ones are in the genus Eleodes. Not so fast, my friend! The genus Coelocnemis, with seven species in the western U.S. and adjacent southern Canada, might be what you are looking at instead.

I won’t make you wait. I know you are already asking how to tell the difference between Eleodes and Coelocnemis. In my experience, Coelocnemis usually has a broader, more angular pronotum (top of thorax) than Eleodes, but there is a better character to use in separating the two genera. Coelocnemis has distinct, parallel lines of yellow pubescence (short, soft hair) on the inner surface of the tibia segment on each leg. Eleodes does not have this feature. Indeed, “Coelocnemis” translates roughly to “hollow shin,” describing the groove between the lines of hairs.

Both kinds of beetles lack flight wings, and have fused elytra (wing covers) to help prevent water loss. They actively wander in the cool of the night to further prevent dessication and overheating.

Habitat can be an important clue to the identity of a given specimen as well. While both genera are found most frequently in xeric habitats, Eleodes is more typical of barren, desert ecosystems. Coelocnemis is common in pine forest habitats, or oak-conifer woodlands, where it is usually found in or under rotten logs.

Behavior is not a good way to distinguish the two genera. Both do the “headstand” behavior in self-defense. They both secrete smelly defensive chemicals from glands at the tip of the abdomen that effectively repel all but the most determined vertebrate predators. Grasshopper mice are well-known for disarming the beetles by jamming the bug’s rear end into the ground and then eating the head and thorax.

Coelocnemis in defensive "headstand"

The larvae of tenebrionid beetles are most familiar to us as the “mealworms” we purchase as bait, or to feed captive reptiles, amphibians, and other exotic insectivores. The larvae of Coelocnemis do resemble mealworms, except A.) they are a lot larger in size and B.) they are armed at the rear with a pair of hook-like prongs and a series of much smaller teeth behind the prongs.

The adult beetles feed on plant detritus, lichens, fungi, seeds, and related matter from which they get precious little water. They are durable animals that can live at least three years. They hibernate in small groups in dry, protected niches.

Sources: Eaton, Eric R. and Kenn Kaufman. 2007. Kaufman Field Guide to Insects of North America. Boston: Houghton Mifflin Company. 392 pp.
Evans, Arthur V. 2008. National Wildlife Federation Field Guide to Insects and Spiders of North America. New York: Sterling Publishing Company, Inc. 497 pp.
Evans, Arthur V. and James N. Hogue. 2006. Field Guide to Beetles of California. Berkeley: University of California Press. 334 pp.
Harpootlian, Phillip, et al. 2006. “Genus Coelocnemis,” Bugguide.net