68 PLATE XXXI. 
of a moft fingular ftructure. This happens about the latter end of 
May, or beginning of June, if the weather proves favourable ; they 
will then be found in fhallow ftanding waters, crawling on the grafs or — 
plants which grow there, or they may be taken floating on the furface 
of the water. The Body confifts of twelve annular divifions, whereof 
- the Head and Tail are two; the Tail has a verge of hairs, which, 
' when entirely expanded, fupport the creature on the furface, with its 
head downwards. If it withes to defcend, it contracts the hairs in the 
form of a wine glafs, or entirely clofes them at the end; and when 
again it is rifing to the furface, it forces a bubble from a {mall aperture 
in the center, which immediately makes a paflage for its afcenfion.— 
Tt changes to the Pupa ftate, and about the middle of uly to the Fly. 
It fubfifts at this time on the neCtar and other juices it extracts from 
the bottom of the corolla in flowers. 
FIG. 
