recently “rediscov-ered” in the SugarRiver in WinnebagoCounty, presents anopportunity to studythe biology of a rareand usually difficult-to-collect mayfly.

This speciesthrives in fast-flow-ing, sandy riversand can be foundfrom late June toearly September.Lying in fine sand,nymphs raise theirthorax, creating avortex that concentrates food particles inthe water. Hatching starts in August withmale nymphs rising to the surface of the

January 2007 OutdoorIllinois / 19

M ayflies are aquaticinsects classifiedin the orderEphemeroptera—aname of Greek origin,

with ephemeros, meaning living only aday, and pteron, for wing. Althoughmayflies have lived on the planet formore than 300 million years, they stilldisplay ancestral characteristics in theform of their upright and unfoldingwings. Illinois streams and lakes histori-cally have supported 107 mayfly speciesbut the current status of mayflies in Illi-nois is unknown.

The sand-filtering mayfly(Homoeoneuria ammophila), oncethought extirpated from Illinois but

stream before dawn—struggling fromthe nymphal skins while riding thewaves and searching for females just aninch above the water. By 7 a.m.,females leave the water, are grabbed bya male and they mate on the wing.Females then fly back to the stream,belly smacking the surface, and collec-tively expel millions of eggs. By 10 a.m.,all is done and only the carcasses, float-ing down the river, remain.

These behaviors are largely unknowneven to the scientific community. Fewothers, perhaps only fisherman, everwitness this brief event. Locating addi-tional populations and genetic analysesare needed to form protection strategiesso others can witness the amazingannual emergence.

—Dr. R. Edward DeWalt andMs. Dawn Dockter, Illinois Natural

History Survey, Champaign

Sand-InhabitingMayfliesPhotos By Dawn Dockter

Ongoing research providing information on an imperiledguild of aquatic insects.

AdultAdult

NymphsNymphs