AQUATIC INSECTS IN NEW YORK STATE 329 
tabulated in the form of keys, to enable any one having an ele- 
mentary knowledge of entomology to identify members of this 
interesting group of insects. 
The Simuliidae are treated at greater length than the others, 
more material being at hand for the study of this family. In 
the descriptions of the wings of the adult, the nomenclature of 
Comstock and Needham (1898) has been followed. 
The aquatic larvae of the Diptera may be distinguished from 
aquatic larvae of other insects by the absence of true, jointed 
thoracic legs; in having abdominal prolegs, or in being entirely 
legless; in the most degenerate forms the head is reduced and 
retracted within the pointed apex of the thorax, and no appen- 
dages of the imago are visible. Their pupae either have promi- 
nent prothoracic dorsal spiracles, often borne at the end of the 
antennaelike processes, or the pupa is formed in the hardened 
larval skin. The adults have but two wings, or in a few rare 
cases are apterous. The presence of the balancers and the 
absence of caudal filaments distinguish them from the males 
of the Coccidae. The most familiar examples are house flies 
and mosquitos. 
The Diptera in general are divided into two suborders: 
Larvae with a differentiated head; pupae free or inclosed 
in the larval skin; in either case the larval skin bursts 
for the extrication of the pupa or imago in a T-shaped 
opening on the back of the anterior end, or rarely in a 
transverse rent between the eighth and ninth abdominal 
rings. The imago lacks the frontal lunule and ptilinum. 
Examples are the gnats, midges, crane flies, horse 
flies, snipe flies, robber flies, ete. (Nematocera and Bra- 
RE Ee oe ora bose i 2 a ae y ix a, wide Sov dna Orthorrhapha 
Larvae without differentiated head; pupae always inclosed 
in the hardened larval skin (forming the so called pupa- 
rium); the imago always escaping from the anterior end 
through a circular orifice. Wrontal lunule present; ptil- 
inum usually present. Examples of this suborder are flesh 
and horse flies, bots, drone flies, ete. Among these are but 
few having aquatic larvae—a few Syrphidae, some of the 
Sciomyzidael and other Acalyptrate Muscids....Cyclorrhapha 
1See N. Y. State Mus. Bul. 47. 1901. p.577. 
