Unidentified Sciarid Larvae and Pupae

Asked about the larvae that travel in large masses, sciarid specialist Rob Deady responded (9/23/2014):

"From what I gather there are several species that do this but the one I'm most familiar with is Sciara militaris (great species name) and S. thomae. See: http://www.diptera.info/forum/viewthread.php?thread_id=55348. As well as these species, apparently Cratyna perplexa, Ctenosciara hyalipennis, Bradysia bicolor and many other Sciara also may exhibit this behaviour. I wonder does Sciara humeralis exhibit this behaviour also. I found huge amounts of it in a boggy lakeside reed bed over the summer and apparently it always is found in extremely wet environments. It has to be a response to excess water logging I reckon, water is definitely the trigger but who knows.

"They generally crawl over a mucous that each larvae produces and they march in search of a drier area in which to pupate from little excerpts of work I have read and generally not to feed but this needs to be studied further. It has been suggested by some authorities that they migrate to avoid excess pressure from competition, another possibility perhaps."

In North America, so far only Sciara species are known to exhibit this behavior; see Pereira et al. (2023).

Fungus Gnats and Gall Midges:

Pereira, Thalles P. Lavinscky, Kai Heller, Mitsuaki Sutou, and Derek S. Sikes. 2023. Discovery of snakeworm gnats in Alaska: a new species of Sciara Meigen (Diptera: Sciaridae) based on morphological, molecular, and citizen science data. Integrative Systematics 6(2): 91–111. (online)