Order Ephemeroptera (Mayflies)
 
 
 
 
 
 
 
 

Labrum (la) with medial notch on margin furthest
away from body; antennae long
er than 2-3 times the width of the head

Labrum (la) without medial notch on margin furthest
away from body, OR labrum with notch and maxillae (ma) with pectinate (comb-like) spines; antennae short
er than two times the width of the head