Several of the insect fossils collected from the Green River Formation (45–50 mya) that I am photographing appear to be flies, and specifically members of the “primitive” suborder Nematocera. This is not surprising, as the G.R. Formation of Colorado, Utah, and Wyoming, is composed of shales derived from volcanic ash sediments that were laid down in a system of large, shallow lakes. Most (all?) nematoceran flies are aquatic to some degree in the larval stage, thus the adults are also closely associated with such habitats for mating and egg laying.
Diptera: Chironomidae | USA: Colorado, Garfield, Hwy 139, Douglas Pass
This particular fossil looked to me a lot like the more elegantly preserved fossil of another fly that I posted a few days ago, which at the time I thought represented a member of the family Mycetophilidae (fungus gnats) or Sciaridae (black-winged fungus gnats). Several knowledgable specialists offered their opinions in comments at this site and at Facebook’s Diptera forum (my thanks to all who offered their opinion), with most settling on Mycetophilidae and Vlad Blagoderov further suggesting subfamily Mycetophilinae. The fossil posted here seemed to me to represent a dorsal view of the same species, but, of course, I’m a coleopterist—so what do I know? Indeed, dipterist Dr. Chris Borkent believes this is actually a species of Chironomidae (common name simply “midges”)—also a nematoceran but differing from Mycetophilidae by their longer front tarsi and longer, relatively narrower wings. Males of the family have thickly plumose (“feathery”) antennae, which are not visible in this specimen and thus suggesting it might be a female. I wouldn’t doubt Chris’ identification for a second, as he comes from good stock—his father is Art Borkent, a world expert on several families of nematoceran dipterans. Art also agreed after seeing the photo that it looked like a female chironomid midge, so that is what I am going with. Thank you, Chris and Art, for your help in identifying this fossil!
Complete fossil specimen (63 mm x 52 mm maximum each axis).
Copyright © Ted C. MacRae 2012
Saturday was my birthday, and for most of my adult life it has been tradition to take the day off for the Annual-Birthday-First-Bug-Collecting-Trip-of-the-Year™. At Missouri’s middlin’ latitudes, late April is normally a tad early—at least for the groups that interest me, but it’s less about serious bug collecting and more about kicking off the season in a bit of a special way. Normally if my birthday falls on a weekend, as it did this year, I’ll take off the adjacent weekday instead (it’s not special if you can’t take off any time from work). However, this year that wasn’t possible due to events at work far beyond my little sphere of influence (conspiracy #1), thus Saturday itself became the planned day. My family and I celebrated Friday evening so I could have the whole day on Saturday, and as we ate we watched news reports of suspected tornadoes ripping through St. Louis just to our north and a little further south (conspiracy #2). Forecasts called for rain continuing well into the following week (conspiracy #3), and for the first time in… well… ever, I had the feeling the ABFBCTOTY might be cancelled due to weather. Waking the next morning, I turned on the television to see precipitation forecasts across the state (1″ in northwest Missouri to 6″ in southeast Missouri) amidst stunning chopper video footage of neighborhoods destroyed and lives turned upside down.
I stopped counting conspiracies and hugged my girls!
That evening, I turned on the mercury vapor lamp over the garage door for the first time since last year to see if anything might show up. We live in a heavily wooded area of western St. Louis Co. featuring relatively intact mesic upland forest dominated by several oaks, hickories, and sugar maples that harbor a nice diversity of woodboring beetles and treehoppers (though I didn’t expect to see these on this night). The night was cool and clammy—nothing but a few moths and flies showing up. Some of the flies were quite small, and some were extraordinarily small—not more than 1 or 2 mm in length. Tiny little specks of life! I thought it might be fun to get in some practice time with the 65mm lens, and the sampling shown below represents a few of those taken with the lens maxed out at 5X (resulting in a frame width of ~5mm):
Male non-biting midge (Chironomidae) | St. Louis Co., Missouri
Female non-biting midge (Chironomidae) | St. Louis Co., Missouri
Moth fly (Psychodidae) | St. Louis Co., Missouri
Same individual as above, chased onto a finished wooden table to highlight its dense pilosity
Copyright © Ted C. MacRae 2011