What's in Dat Scat?

Sometimes you have to literally get down and dirty to find interesting insects. Poking into animal dung, affectionately known as "scat," is a pretty smelly, gross business, but it can yield a diversity of insect life you are unlikely to see otherwise. A case in point came on April 13 when I visited the Bluestem Prairie Open Space along the edge of Johnson Reservoir just southeast of Colorado Springs.

Two half-buried Trox sp. and one red and black dung beetle, Aphodius fimetarius under coyote scat.

While dogs are not permitted in the area, I suspect the locals probably bring them in anyway, judging by the tracks and the scat I come across. Still, the overwhelmingly most common canines are coyotes, and their dung invariably contains lots of fur from their prey. This makes their excrement attractive to beetles more commonly found on carrion and mummified carcasses.

Hide beetle, Trox sp., on coyote scat, facing left

Hide beetles in the family Trogidae normally visit the dried-out remains of an animal body when little is left but skin and bones. Indeed, that is what they eat as adults and larvae, along with feathers, fur, and connective tissue. Apparently coyote dung is the next best thing to a dead body. I found a total of three Trox sp. on just one piece of manure. These beetles are almost invariably caked in gunk so as to be nearly unrecognizable as insects, or animals of any sort, really. When disturbed they go voluntarily comatose, so convincingly that I have given them up for dead, stiff specimens. I've been startled by having them re-animate in a vial or cup after several minutes.

Fully active Trox sp.

Another surprise on this chunk of poop was a skin beetle, Dermestes fasciatus or D. marmoratus, I am not sure which. Again, these beetles are usually much more common on carcasses in advanced stages of decomposition, including wet bones.

Skin beetle, probably Dermestes marmoratus

There were, however, some honest-to-goodness dung beetles in another piece of coyote scat that was a little....fresher, if one can apply that term to anything that doesn't smell the part. Aphodius fimetarius is a little red and black dung beetle that was introduced to North America from Europe probably a century or more ago. It is now widespread and common here, usually in cow pats. The larvae live and feed in the manure, then dig into the soil beneath it to pupate. There is probably one generation per year.

"Tumblebug," Canthon simplex, unfortunately lying trampled on a trail

The other dung beetle I found was one of the dung-rollers or "tumblebugs" as they are affectionately called. This species, Canthon simplex, is relatively tiny, adults measuring only 7-8 millimeters. The adults tear off a pea-sized chunk of poo and roll it into a ball, either females alone or in pairs with males. Rolling the ball away minimizes conflict with other dung beetles. Once a suitable site is located, the female buries the "brood ball" and lays a single egg inside. The grub that hatches feeds inside, eventually pupating within the now hollow sphere.

"Tumblebug," Canthon simplex

While I was looking for the dung beetles, a very small rove beetle, family Staphylinidae, raced up a grassblade and flew off before I had a chance to secure it. Rove beetles are predators of other insects, and many species visit dung and carrion to feed on fly maggots. Rove beetles are slender, almost serpentine, with shortened wing covers (elytra), and so may be mistaken for earwigs at first glance. Staphylinids are so diverse that identifying them is next to impossible for anyone but an expert; and it also frequently involves detailed examination of the male's genitalia.

Typical rove beetle, family Staphylinidae

Maybe you are not "into" dung fauna, at least not if it requires pawing through it with or without gloves and/or various instruments. Ok, no one can blame you; but before you dismiss the power of poo altogether, consider my upcoming post "What's on dat scat?" You will be surprised all over again.

Source: Ratcliffe, Brett C. 1991. "The Scarab Beetles of Nebraska," Bull Univ Nebr State Mus. Vol. 12: 333 pp.

Anteater Scarab Beetles

Beetles have truly bizarre lifestyles in general, but one of the most astonishing is the life cycle of "anteater scarab" beetles in the genus Cremastocheilus. These are rather small, non-descript insects that are easily overlooked. What a pity. I guarantee you will want to find one yourself after reading this story.

This is the time of year when you are most likely to encounter these beetles. They are dispersing themselves to find new hosts. They fly very well, and fast, but crash land in places frequented by scouting ants during the day.

There are roughly 35 species of Cremastocheilus currently recognized in North America north of Mexico, but the genus is being revised. Most are dull black, about 10 millimeters in body length, flattened, and very angular. The exoskeleton is exceedingly dense, often with pits or wrinkles, or both. These are heavily armored insects, and for good reason.

Anteater scarab beetles are just that: they feed as adults on the larvae and sometimes the pupae of ants. The host ant species are mostly mound-builders in the genus Formica, but other hosts include honeypot ants (Myrmecocystus), cornfield ants (Lasius), and carpenter ants (Camponotus). Harvester ants (Pogonomyrmex and Veromessor), and spine-waisted ants (Aphaenogaster), are frequent hosts for anteater scarabs in the southwest U.S. The heaps of vegetation created by some Formica species, known as "thatching ants," provide the protection and food resources needed for Cremastocheilus beetles to complete their life cycle.

Cremastocheilus being dragged by Formica ant

How do the beetles gain entry to an ant nest protected by hundreds, if not thousands, of short-tempered worker ants? It appears that the beetles "play dead" in areas heavily trafficked by roaming worker ants. The death-feigning posture of anteater scarabs is highly convincing: motionless, with legs outstretched. Thatching ants are scavengers and sometimes predators, so any morsel of protein is quickly snatched up and taken back to the nest.

The antennae of Cremastocheilus are normally protected in grooves under the head, but here they are seen on an active specimen

The female beetles lay their eggs singly in the soil around the periphery of the nest mound, and the larvae feed on the decaying vegetation that the ants have more or less composted.

Larvae are pretty much ignored by the ants, though the grubs are capable of fighting back by striking attacking ants with their jaws, and secreting repulsive liquids from their mandibles and anal glands.

The beetle grubs progress through three instars, an instar being the period between molts, before pupating in oval chambers they create from soil particles. The cycle from egg to adult takes about four months, adult beetles emerging from their pupal cells in late summer or early fall.

The newly-emerged beetles make their way slowly to the center of the ant nest, accumulating the colony scent along the way and presumably rendering themselves incognito. The adult ants are also largely dormant during the winter. Come spring, the beetles begin feeding on ant larvae.

Close-up of mentum on underside of the beetle's head © Jeff Gruber and University of Wisconsin (Madison) Entomology Dept.

The beetles have unusual modifications to their mouthparts. The mentum is enlarged and shield-like, covering the other mouthparts from below. The maxillae are modified into sharp appendages that pierce the soft cuticle of ant larvae and pupae. The beetle's mandibles are much reduced and function only to help transport liquid food to the mouth.

Cremastocheilus beetles have special brushes of hairs on the hind angle of the pronotum (top of thorax) where it meets the "shoulders" of the elytra (wing covers). These brushes are called trichomes. The hairs are attached to glands that secrete a liquid substance that was originally interpreted as an attractant, or at least a pacifier, to the ants. This is apparently not the case, and the trichomes remain something of a mystery.

Anteater scarabs reach their greatest diversity in the desert southwest, but they can turn up almost anywhere. Do a double-take when you expose an ant colony under a stone or board. There may be a Cremastocheilus or two among the ants. Excavated ant colonies usually yield twenty or thirty beetles or their larvae, but some nests may host up to 200.

Sources: Alpert, Gary D. and Paul O. Ritcher. 1975. "Notes on the Life Cycle and Myrmecophilous Adaptations of Cremastocheilus armatus (Coleoptera: Scarabaeidae)," Psyche, 82 (3-4): 283-291.
Hölldobler, Bert and Edward O. Wilson. 1990. The Ants. Cambridge, Massachusetts: Belknap Press (Harvard University Press). 732 pp.
Mynhardt, Glené and John W. Wenzel. 2010. "Phylogenetic analysis of the myrmecophilous Cremastocheilus Knoch (Coleoptera, Scarabaeidae, Cetoniinae), based on external adult morphology," ZooKeys 34: 129-140.
Ratcliffe, Brett C. 1991. "The Scarab Beetles of Nebraska," Bull. Univ. Nebr. State Mus., vol. 12: 333 pp.

A Flower Scarab, Euphoria fulgida

Last year, on June 15, 2013, my wife Heidi captured an interesting beetle at the Cheyenne Mountain Zoo where she works as a keeper for gorillas, orangutans, and other primates. What transpired after she posted images on Bugguide.net was surprising and exciting. It turned out that the beetle was a flower scarab, Euphoria fulgida, which had not been recorded in Colorado since 1902.

I was delighted that she even recognized it as a beetle, because she saw it in flight and this species is a remarkable bee mimic. Scarabs in the subfamily Cetoniinae, collectively known as fruit and flower chafers, have a special “hinge” on the body that allows the membranous hind wings to deploy for flight while the wing covers (elytra) remain closed. The insects are fast, powerful, and erratic fliers, so I am also surprised Heidi managed to catch the beetle.

© Mark E. Marcuson in Ratcliffe, 1991

Since I was out of town when all of this happened, and without ready internet access, I couldn’t help her identify the specimen. So, she posted her images to Bugguide.net. By June 17, she had a preliminary identification, and then Dr. Frank Krell, a scarab expert conveniently located at the Denver Museum of Nature and Science, confirmed it on June 18.

Complicating matters is the great degree of variation in color for Euphoria fulgida, sometimes called the Emerald Euphoria. Many specimens from the eastern U.S. are indeed metallic green, with some reddish color around the edges. Margarethe Brummermann and I found specimens in the mountains of southeast Arizona that are metallic blue-black (Note: these are now recognized as a separate species, E. monticola).

An Arizona specimen, now known as E. monticola

The ones here in Colorado mostly have a bright metallic blue-green pronotum (top of thorax), and mostly burgundy elytra with white speckling.

Euphoria fulgida is a fair-sized scarab, adults measuring 13.4-19.8 millimeters. This is a widespread species found from Ontario and Quebec to Florida, west to Nebraska, Colorado, and New Mexico. Look for the beetles flying during the day, usually close to the ground. They enjoy feeding on sap exuding from wounds on trees, especially oak. Occasionally they visit the flowers of dogwood, sumac, thistle, and other plants for nectar and pollen. The adults are most common in May and June, but can persist well into July.

The life cycle of this flower chafer takes about a year. Larvae reared under laboratory conditions and fed on manure and ungerminated wheat seeds took an average of 122 days to mature. The larvae enter a quiescent pre-pupal stage in September or October, and pass the winter this way. Pupation takes place in the spring, often under logs in moist habitats, with the adult beetles emerging mostly in late spring and early summer.

Fast forward to this week. Monday, June 2, Heidi and I went hiking in Cheyenne Mountain State Park, just south of Colorado Springs. Above the floor of the plains, the habitat changes to mixed evergreen forests with an understory of Gambel’s Oak and other shrubs. By late morning and early afternoon we were encountering a fair number of Euphoria fulgida weaving their way through the understory shrubs. We were also lucky enough to notice a trio eating sap from an oak twig. Altogether we saw probably close to a dozen specimens. Nowhere does this species appear to be abundant, but where you see one there are usually others in close proximity.

This is one of my favorite beetles, I must admit. I first encountered them on Marathon Key in Florida in June, 1978, and at first thought they were bees. (Note: Those Florida specimens are now recognized as a separate species, E. limbalis, per a revision of the genus by Jesus Orozco in 2012). I hope you have the pleasure of finding them in your own explorations.

Sources: Evans, Arthur V. 2014. Beetles of Eastern North America. Princeton, New Jersey: Princeton University Press. 560 pp.
Krell, Frank-Thorsten. 2010. Catalogue of Colorado Scarab and Stag Beetles (Coleoptera: Scarabaeoidea), Based on Literature Records. Denver: Denver Museum of Nature and Science technical report 2010-4. 86 pp.
Ratcliffe, Brett C. 1991. “The Scarab Beetles of Nebraska,” Bulletin of the University of Nebraska State Museum vol. 12: 1-333.
Ritcher, Paul O. 1966. “White Grubs and Their Allies,” Studies in Entomology. vol. 4. Oregon State University Press. 219 pp.
Special thanks to Margarethe Brummermann and Eddie Eichinger for the clarification of the new species recently split from E. fulgida.

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.

Wasp Wednesday: Triscolia ardens

Have you ever been involved in a hit-and-run accident? If so, then you know what it feels like to be a scarab beetle grub being attacked by a scoliid wasp. The only difference is that the insect encounter is no accident. Female scoliid wasps actively seek out the beetle grubs as hosts for their larval offspring. Here in southern Arizona, one of the largest and most conspicuous of the scoliids is Triscolia ardens.

T. ardens is the only member of its genus in North America north of Mexico. It occurs from Texas to southern California and is relatively common. Females are robust, with short antennae. Males have long antennae and sport a three-pronged "pseudosting" at the tip of the abdomen. The remainder of this post will treat scoliids in general because so little is known about the biology of individual species.

Scoliids of both genders can be found visiting flowers, especially milkweed, seep willow (Baccharis), saltcedar (Tamarix), desert willow (Chilopsis), mesquite (Prosopis), scalebroom (Lepidospartum), and buckwheat (Eriogonum). At the end of the day, the wasps bed down singly on vegetation, remaining alert but not not terribly motivated to move as the desert temperatures begin to fall.

Their life cycle can be generalized as follows. The female wasps fly low over the ground, somehow divining the presence of subterranean scarab beetle grubs. Once one is detected, the wasp digs it up, using her densely spiny legs to send the soil flying. Once she unearths the grub, she stings it into paralysis. This allows her to lay a single egg on the grub. After she accomplishes her mission, she re-buries the grub and flees the scene of the crime (some species have been observed moving the grub deeper into the soil and fashioning an earthen cell around it before depositing an egg and sealing the tunnel). The beetle grub apparently never recovers from its coma. The egg of the wasp hatches, and the larva that emerges will feed as an external parasite on its host for about a week or two before spinning a silken cocoon and pupating. Most North American scoliids overwinter in the pupal stage.

The size of the mature wasp is dependent on the size of the host beetle grub. Even the largest Triscolia ardens seldom exceed about 30 millimeters in body length, but one frequently finds “dwarfs” that obviously suffered a lack of nutrition in their youth. Tropical scoliids, however, are among the largest (certainly heaviest) wasps in the world, exceeding 50 millimeters in body length.

Other online resources include this PDF on scoliid wasps of Florida. It is an excellent introduction to the family as a whole, treating Florida scoliids in particular. Another PDF on Scoliidae of California addresses some southwestern species but it appears incomplete.

Clearly, much remains to be learned about these highly attractive and obvious wasps. Any documentation with video is likely to be a first, or nearly so; and host associations are almost entirely lacking for our native scoliids (some species have been introduced to the U.S. to control exotic scarab pests).