by Bob Androw
As I begin to write this, it’s early March, the sun is shining, the temperature outside is climbing over 50°F and I’m starting to think… “I need to go look for some deer poop!”
As an entomologist, I’ve developed a mental calendar not based on seasons or months… but rather on what species of insects are likely to be out and about on any given day of the year. Once summer arrives, the specificity disappears and it just becomes a question of whether it’s a “good bug day” or not – based entirely on the weather and my chances of prying myself out of the museum (or the house, in these new times) to go somewhere and chase them.
During autumn, the onset of wet weather and cooling temperatures gradually reduces the number of active insects. Like most organisms, I tend to head for shelter from the outside environment, settling indoors to wait out the winter. Of course, winter is time for “bug work” as well – but rather than hunting living specimens, time is dedicated to catching up on the lab work set aside during ‘collecting’ season. This entails pinning and labeling specimens collected earlier in the year, performing identifications, data-basing specimen records, and working on manuscripts.
But then there’s spring – that pivotal period that influences one to keep checking the weather forecast, hoping for warming days. This seemingly never-arriving season focuses one’s attention on how fast the last snow is melting off. It’s a time that has me searching for signs of plant shoots breaking the soil surface and tree buds exhibiting tiny slivers of green to announce the upcoming burst of foliage.
Once these signs converge to indicate spring is just around the corner – it’s time to test the theory that winter is finally ending by – you got it! – going to look for deer poop!
Now, don’t get me wrong – deer regularly poop all year round – which is good for them – but during the first warm days of spring – or more accurately the warmest days of late winter – a little beetle becomes active and begins its own search for deer dung.
The species Dialytellus tragicus (Schmidt, 1916) is a mere 3mm in length and one of only two species in the genus Dialytellus. My favorite location to search for it is the museum’s field research station, Powdermill Nature Reserve, in the Laurel Highlands. Dialytellus tragicus is found in forested areas of the northeastern United States, but is sporadic in distribution and never seems to be overly common. The other species in the genus, Dialytellus dialytoides (Fall, 1907), is more widely distributed in the eastern states, much more common, and is taken frequently in pitfall traps. The genus Dialytellus is a member of the large subfamily Aphodiinae in the large family Scarabaeidae, the scarab beetles.
The Aphodiinae is a diverse group of small to tiny beetles, with over 400 species occurring in the United States and Canada. Nearly all of them are specialists on animal dung for feeding as adults and for provisioning their larvae with food. Many are considered ‘generalists’ which means they will utilize whatever dung they find – from cattle, horses, deer, pigs, dogs, and even humans (Oh, there are some stories to tell there…). Some species dig tunnels in the soil under dung and create brood chambers where they lay eggs on dung brought down from the source on the ground surface, but most lay eggs directly in the dung and the larvae develop within.
A fair number of aphodiine species are ‘specialists’, utilizing dung from only certain species of animals. In the Great Plains region of the U.S., the group reaches its greatest diversity of species for North America, with most species being obligate associates with prairie dogs, living in the burrows and feeding in the dung ‘middens’ that the resident prairie dogs create. In the Pacific Northwest, aphodiines are often associated with the burrows of marmots. In the Southeast, many species are associated only with pocket gophers, while a few have evolved to live only in the nests of squirrels, or packrats, feeding on decaying nest materials. Some of these specialized beetles have even evolved to live in ant nests, feeding on plant detritus in the ants’ garbage heaps.
Dialytellus tragicus is able to pull me out of the house and into the woods in late winter on an annual search first for piles of deer dung, and then if lucky, beetles. The beetles can be found inside the deer dung pellet, which means the search entails splitting dung pellets to find the precious one with a beetle inside. Thankfully, deer dung is dry and hard and has little odor, so the process is less offensive than it sounds. Still, I would guess that laying on one’s side in the leaves, splitting pellets with a forceps as if they were little coconuts with prizes inside, isn’t a common way to celebrate the onset of Spring – no Facebook group for us folks!
Most specimens that I have collected have been found during the middle two weeks of March, always on days where the temperatures have been over 50°F for at least the preceding three days. It takes a few days of warmer weather to get the beetles up and moving. I’ve learned that searching for them later in the year – say mid-April – never produces specimens of D. tragicus, but instead produces numerous specimens of another aphodiine, the extremely abundant generalist, Oscarinus rusicola (Melsheimer, 1845). Circumstantial evidence would suggest that as D. tragicus evolved alongside O. rusicola in eastern forests of North America it shifted its period of activity to earlier in the season to avoid competition for resources with the more abundant O. rusicola.
By the end of February of any normal year, the urge to get out of the house and into the woods starts to become irresistible, but the insects are more patient – waiting for the perfect number of degree-days to become active. Knowing this little beetle is out there early – and is not necessarily easy to find – provides the perfect impetus to shake off the winter dust and go out to look for it. In a year like the one we’ve all suffered through, this little beetle is even more appreciated as an excuse to rouse and get moving again.
Bob Androw is a Collection Manager for Invertebrate Zoology. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.
The BSF – Leveraging Our Collections and Expertise to Help Fight Invasive Species
Carnegie Museum of Natural History Blog Citation InformationBlog author: Androw, Bob
Publication date: April 2, 2021