Another Odd Carrion Beetle

I do not know what it says about our field excursions this year, or the state of our local fauna, or the state of our country, that we are finding carrion beetles to be the most interesting creatures we have observed so far. Case in point is the Western Spinach Carrion Beetle, Aclypea bituberosa, spotted by Heidi on Monday, February 20. We were walking the Front Range Trail in Clear Spring Ranch park, an El Paso County, Colorado park when we crossed paths with this unique beetle.

I happen to like spinach, especially fresh spinach, so I was disappointed to learn that the Western Spinach Carrion Beetle is considered an occasional pest of that plant. The adult and larval stages both feed on a variety of plants, including pumpkin, squash, beets, wheat, radish, rhubarb, potato, lettuce, cabbage, turnip, and rapeseed. Beets and spinach suffer the most damage in May. Aside from these crops, they consume lamb's quarters, povertyweed, and other native and introduced members of the plant family Chenopodiacea; and also nightshade (family Solanaceae).

The adult beetles emerge early in the spring, so apparently finding one at this time of year is not too unusual. Females lay their eggs in soil shortly thereafter, and in about a week the larvae hatch. The larvae feed during the day on young leaves and shoots of their host plants, hiding in the soil at night. There are three instars, an instar being the interval between molts of the exoskeleton to allow the insect to grow larger. The first two instars each last about five days, the third instar taking an average of fifteen days before the molt into the pupa stage. Mature larvae, black in color, are about 11-15 millimeters long. The pupa is buried one to two inches deep in the soil. The adult beetle emerges from the pupa in about three weeks. Thus there is one generation each year, the beetles overwintering as adults.

Note the "cleft lip" just behind the jaws

These are small insects as carrion beetles go, only 12-17 millimeters in length. They resemble several other carrion beetles but for a couple of features. The diagnostic character for this genus is the cleft labrum, or "upper lip" if you will, just behind the mandibles. The deep notch leaves no doubt as to the identity of the beetle. There are two species in the genus, but Aclypea opaca, the "Beet Carrion Beetle," is restricted in North America to Alaska and the Northwest Territories. It appears to be native to northern and central Europe, being introduced accidentally to North America.

The other feature that helps identify A. bituberosa is the pair of raised tubercles, one each near the rear of each elytron (wing cover). There are three conspicuous longitudinal ridges on each wing cover as well.

The beetle cleaned up and photographed at home

The Western Spinach Carrion Beetle is just that: a species confined to the northwest quarter of the U.S. and adjacent southern Canada, from British Columbia and Washington state south to central California east of the Sierras, and eastward to northeast Nebraska and southeast Manitoba. It is more common east of the Continental Divide, less so in the Pacific Northwest. The adult beetles are active from March through November, and occur both on the plains and in mountain meadows.

While I find carrion beetles quite fascinating, I cannot help but hope to find less morbid insects in the coming months, creatures that reflect the true optimism of spring. Plus, I need to start eating a little healthier, and this particular beetle is competing for "my" veggies.

Sources: Anderson, Robert S. and Stewart B. Peck. 1984. "Bionomics of Nearctic Species of Aclypea Reitter Phytophagous "Carrion Beetles" (Coleoptera: Silphidae)," Pan Pac Ent 60(3): 248-255.
Essig, E.O. 1958. Insects and Mites of Western North America. New York: The Macmillan Company. 1050 pp.
Monk, Emily, et al. 2016. "Key to the carrion beetles (Silphidae) of Colorado & neighboring states," Colorado University Museum of Natural History.
Swan, Lester A. and Charles S. Papp. 1972. The Common Insects of North America. New York: Harper & Row, Publishers. 750 pp.

A Carrion Beetle That Isn't?

At first glance, the Garden Carrion Beetle, Heterosilpha ramosa, could be mistaken for a darkling beetle or ground beetle. Indeed, only the clubbed antennae, and the five tarsal segments comprising each "foot," betray them as something else (darkling beetles have only four segments in the tarsus of the hind leg). Carrion beetles make up the family Silphidae, but surprisingly, this particular species seems to have a diet of anything but corpses.

I periodically encounter the 11-17 millimeter long, dull black adult beetles crossing the sidewalk in my Colorado Springs neighborhood. The natural habitat here is shortgrass prairie, but I knew this beetle when I lived in the coniferous forests of Portland and Corvallis, Oregon, too. It occurs mostly west of the Rockies and south to Mexico, but ranges east and north as far as Iowa, Minnesota, and Ontario, Canada.

Consulting various references paints and interesting and evolving picture of H. ramosa. Older references used the genus name Silpha, but it is the portrayal of the species as at least an occasional pest that is puzzling. Essig declares that the Garden Carrion Beetle feeds mostly on decaying vegetable matter, but "also attacks garden and field crops, grasses, and weeds. If often occurs on lawns." Presumably it consumes these foods as both an adult and a larva.

The larva is jet black, highly mobile, and resembles an overgrown carpet or hide beetle larva (family Dermestidae, especially genus Dermestes). The tapered body allows the larva to slither effortlessly into cracks and crevices, or easily slip out of a predator's grasp. The speed at which it can travel is rather surprising considering the relatively short legs at the front of the body.

A more contemporary book by Jerry Powell and Charles Hogue asserts that the "Garden Silphid" adults and larvae "are general feeders, consuming living or dead, soft-bodied insects such as maggots, which feed on decaying organic matter in the soil; Silpha sometimes feed on leaves of plants at night."

Arthur V. Evans and James Hogue illuminate the natural history of this species a bit more in the most recent reference I could find in my library. According to their Field Guide to Beetles of California, "The adult is active March through October....overwinters and becomes active the following spring. Eggs ar laid in the soil around a carcass or rotting vegetable matter and take approximately five days to hatch.....The larval stage lasts approximately two to three weeks. The pupal stage lasts 8-9 days." The authors go on to recite the previous conclusion that both the adult beetles and the larvae are "general feeders."

The evolution of our understanding of the impact of H. ramosa comes full circle, from minor crop pest to beneficial organism in the rest of Hogue and Evans' life history sketch: "The adult has been found feeding on dead Devastating Grasshoppers (Melanoplus devastator) and Brown Garden Snails (Helix asper)." Ok, so it is scavenging, but considering the predatory nature of other carrion beetles, it would be no surprise to find it killing injured or otherwise incapacitated pest invertebrates, too.

What else do we not know about this species, or any other insect for that matter? The answer is "plenty." Insects which are not perceived to be of economic importance, either positively or negatively, tend to be under-researched, to put it mildly. Outright ignored is perhaps an even better way to frame it. Pick a "bug," any bug, to study, and chances are you can be something of a hero.

Sources: Essig, E.O. 1958. Insects and Mites of Western North America. New York: The Macmillan Company. 1050 pp.
Evans, Arthur V. and James N. Hogue. 2006. Field Guide to Beetles of California. Berkeley: University of California Press. 355 pp.
Powell, Jerry A. and Charles L. Hogue. 1979. California Insects. Berkeley: University of California Press. 388 pp.
White, Richard E. 1983. A Field Guide to the Beetles of North America. Boston: Houghton Mifflin Company. 368 pp.

More Beetles from Bones

Last week I wrote about a few beetle species that I recovered from nearly dry bones here in Colorado Springs. I now have an update, plus additional species found in carrion on a recent trip to a private ranch northeast of Pueblo. It is interesting to note the succession of carrion beetle fauna over time; and the differences in diversity depending on whether the carcass is a large mammal, small mammal, bird, herp (reptiles and amphibians), or fish.

I went back to the bones I found earlier, and discovered some changes as of April 18. I spotted another Northern Carrion Beetle, Thanatophilus lapponicus, before it quickly disappeared, and more dermestids that I previously identified as Dermestes marmoratus. However, a different, smaller species was now more abundant.

Hide and Tallow Beetle, Dermestes talpinus?

I have decided I cannot readily conclude what species are involved here. Twelve species of Dermestes are recorded from Colorado, many of which look nearly identical to each other. The smaller species present on the bones appears to be the Hide and Tallow Beetle, D. talpinus. It is covered in gold or coppery scales on the pronotum (top of thorax), and silvery scales on the elytra (wing covers).

I also found a single specimen of yet another species that is possibly the Fringed Dermestid, D. frischii.

Dermestes frischii?

My wife and I travelled to Chico Basin Ranch on Monday, April 21, mostly seeking spring migrants of the feathered variety. This is a sprawling, working ranch that straddles El Paso and Pueblo Counties, and is managed for both livestock and native wildlife.

Unfortunately, one of the first birds we came across was a deceased Bobwhite quail. Turning it over revealed a shocking diversity of beetle life.

Rove beetles in the family Staphylinidae are predatory, and the ones that visit carrion feed mostly on fly maggots. They are easily recognized by the shortened elytra (wing covers), and are perhaps reminiscent of earwigs.

Hairy Rove Beetle, Creophilus maxillosus

The Hairy Rove Beetle, Creophilus maxillosus, is enormous by staphylinid standards, measuring 11-23 millimeters. These insects fly well, but quickly dig themselves out of sight when uncovered.

Rove beetle, Philonthus politus

Another rove beetle species, Philonthus politus, was also present. It is much smaller, about 10 millimeters. Special thanks to Philip Howe and Max Barclay for suggesting the genus, and Adam Brunke for volunteering the species. Facebook interest groups are a wonderful thing.

Sexton beetle, Nicrophorus sp.

Two species of the family Silphidae were also under the bird carcass: Thanatophilus lapponicus again, and one of the sexton beetles, Nicrophorus sp. Sexton beetles, also known as burying beetles, are big (11-22 mm or so), stocky, and strong. They often work in pairs to dig under the corpse of a small animal, sinking it into the ground. They then chew the carcass into a literal “meatball,” and the female then deposits a small number of eggs in a crater atop the food ball. She’ll chew up small bits of meat and feed them to her larval offspring, cleaning the food of mold and other potential contaminants in her spare time.

Clown beetle, Saprinus lugens

Clown beetles in the family Histeridae are small, spherical, highly-polished insects that play dead or dig when disturbed. They are predatory on other small insects found in carrion, dung, and other unsavory mediums. This one is Saprinus lugens, a common and widespread species measuring 5-8 mm. Thanks to Alexey Tishechkin for the species identification.

Male Scooped Scarab, Onthophagus hecate

Many dung beetles will also visit carrion, such as the little “Scooped Scarab,” Onthophagus hecate. Males have a broad, forked horn projecting over their heads from the top of the thorax. They battle each other for the right to mate with a female. At only 6-9 millimeters, O. hecate is one of the smaller dung beetles.

Hide beetle, Trox sonorae

Last but not least, were cryptic “hide beetles,” Trox sonorae, in the family Trogidae. They are closely allied to scarab beetles. Trogids are rough in texture, and usually so caked in debris as to be nearly unrecognizable as insects. They also play dead so convincingly as to be easily dismissed as living creatures. They freeze in a random, rigid posture when disturbed. This species is only 8-11 millimeters in size, which only makes it even harder to spot. Trox consume dried skin, feathers, and other material when carcasses are in the last stages of decay.

Silphid carrion beetle larva

Dermestes larva

Later in the day, Heidi and I came across the remains of a large livestock mammal, and virtually none of the beetles found on the dead quail were on this much larger vertebrate. Instead, it was carrion beetle larvae, dermestid larvae and adults, and Red-legged Ham Beetles, Necrobia rufipes. There are three common species of Necrobia, all in the family Cleridae. While most clerids are predators, Necrobia adults and larvae actually do feed on carrion, cured meats, and other dried animal products. They can be pests in museums and taxidermy businesses. Ham beetles are about 4-7 mm., but are a lovely metallic blue. They glint in the sunlight as they run over the surface of a dried corpse.

Red-legged Ham Beetle, Necrobia rufipes

Forensic entomology is the study of insects that infest dead bodies. Blow flies (family Calliphoridae) play the most prominent role in crime scene investigations because they can help ascertain the time of death. The life cycle of flies progresses in a predictable fashion, faster at higher temperatures, slower at cooler temperatures. By collecting adults, larvae, and pupae, a criminalist can determine at what time a body was first visited by ovipositing female flies.

Obviously, other insects play a critical role in decomposition as well, and beetles are chief among them. Those of you with strong stomachs may want to examine animal carcasses you come across, as the insects found there can usually be found nowhere else. Just remember to pack the hand sanitizer.

Beetles from Bones

This past Wednesday, April 9, I went exploring near my home to see what insects are out and about here in Colorado Springs this spring. In my wanderings I stumbled upon a few bones of some large mammal, providing an opportunity to find insects specific to carrion.

I am not terribly keen on handling carcasses, but these leg bones were mostly dry. The ligaments were still intact on one leg, but flies had long lost interest in these remains. Still, it takes little to attract ants, and some kinds of beetles. I managed to find three species large enough for photos, plus a couple very tiny rove beetles (family Staphylinidae) that quickly vanished when I turned over the bones.

The first insect I saw was, oddly, a Small Milkweed Bug, Lygaeus kalmia. Many normally herbivorous Hemiptera are opportunistic scavengers, though, so perhaps the appearance of this insect should not have been terribly surprising. The second insect was one I expected, and present in fair numbers considering the relative size of the carcass: Common Carrion Beetles, Dermestes marmoratus.

Dermestid beetle and Small Milkweed Bug

Dermestids are so efficient at scouring the last vestiges of flesh from bone that natural history museums employ colonies of the beetles to clean skeletons. This particular species, a relative of that indoor pantry pest the Larder Beetle, is a handsome insect measuring 10-13 millimeters. The silvery-gray scales on its otherwise black body make it look quite dapper considering the situations it frequents. D. marmoratus is found from southern California through the southwest, southern Rocky Mountains, and Great Plains states.

Dermestes marmoratus

The most spectacular specimen uncovered was a Northern Carrion Beetle, Thanatophilus lapponicus, also known as the Silky Carrion Beetle. It looks superficially like a giant dermestid, 8-15 millimeters in length, but it belongs to an entirely different family, the Silphidae. This species is holarctic, meaning it ranges across the entire northern hemisphere. In North America it is found in Alaska, Canada, and the northern tier of states in the U.S., plus the Pacific states to Baja, Mexico, and the Rocky Mountain states. The adult beetles have been found from March to October. Perhaps its hairy body helps to insulate it against cooler temperatures.

Thanatophilus lapponicus

The last beetle species I collected was a type of sap-feeding beetle in the family Nitidulidae. At only 3-5 millimeters, Nitidula ziczac is difficult to spot, let alone get a clear image of. Despite their name, sap-feeding beetles are highly diverse in their appetites. Some species are found in abundance inside yucca flowers, for example. N. ziczac is a well-known associate of carrion, found in North America mostly from the Great Plains westward, as near as I can tell from various references.

Nitidula ziczac

What truly amazes me about carrion-inhabiting insects is how they manage to locate such a scarce resource. They need the energy to fly to far-flung bodies, at just the right time. Certainly their olfactory powers are light years ahead of us humans (I detected absolutely no odor from these particular bones), and tuned specifically to aromatic compounds liberated during decomposition. However they do it, thank goodness they do, or we would be forever tripping over dead animals, before becoming deathly ill ourselves.

Source: Evans, Arthur V. and James N. Hogue. 2006. Field Guide to Beetles of California. Berkeley: University of California Press. 336 pp.