Friday, December 21, 2012

Spring Comes Early to the Doyles River: The Small Minnow Mayfly, Heterocloeon amplum -- even a Spiny Crawler

Spring insects already?  Yes indeed.  I not only found several H. amplum small minnow mayflies at the Doyles River this morning, I also found this little beauty --

a spiny crawler mayfly, genus Ephemerella (probably E. invaria)!  H. amplum is one of three small minnow mayflies that we typically see in the winter and early spring.  We're more likely to see it in January through March -- but it's only December.  Still, these insects were tiny (H. amplum nymph, 5 mm; E. invaria nymph, 2.5 mm): the wing pads are hardly visible at this stage of the game.   On February the 6th of this year, I found this H. amplum nymph and this E. invaria nymph at this very same spot in the Doyles.

They grow up in a hurry!  We'll be seeing a lot more of both of these nymphs in the months ahead, but it's always neat to find the first of the season.


But it is still winter, and winter insects were plentiful in my findings this morning.  Lots of small winter stoneflies and lots of Perlodid stoneflies, Clioperla clio (the "killer"!).   And, again, as I did two weeks ago, I found Glossosomatids (saddle-case makers), Uenoids (genus Neophylax), and Apataniids (genus Apatania) -- a real mix of caddisfly larvae.  I left the Glossosomatids alone, but I did take some photos of the Uenoids and Apataniids, photos that help us distinguish the two.



And, Unenoid and Apataniid side-by-side:

Since these families are found at the same time of year and make similar cases and can be found attached to the very same rocks, I'm not surprised that, in the past, I've thought all of these larvae were Uenoidae in family terms.  As you'll recall, it was not until 12 days ago (12/9) that I realized that some of the Uenoids I find every year are actually Apataniids!  You might also recall that the shape of the case is one thing that can help us distinguish the two: Uenoid cases tend to be rectangular, tube-shaped, Apataniid cases are tapered, "cornucopia" shaped.  (See Steven Beaty, "The Trichoptera of North Carolina," p. 85.)  But remember, we can only be sure of the family ID by looking at the meso and metanota.


The anterior, front edge, of the mesonotum is "emarginated," and while sclerites are lacking in the sa 1 position, there are two visible setae.


The leading edge of the mesonotum is not emarginated -- it's straight across -- and in place of the sa 1 sclerites on the metanotum, there is a transverse band formed by about 20 setae.

If you're out sampling streams and doing family level ID, be on the look out for both of these insects. But exact identification does require microscope work: these larvae do not abandon their cases until they're preserved.

Next on the agenda -- a check-up on those Strophopteryx large winter stoneflies.

Apataniidae larva; Apatania incerta.

And a spiny crawler and small minnow mayfly also found this morning, even smaller than those pictured above: 2 mm and 3.5 mm respectively.

No comments:

Post a Comment