AQUATIC INSECTS IX 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 tliis 

 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 witii a differentiated bead; 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 arc the gnats, midges, crane flies, liovse 

 flies, buii)e flies, i-obber flies, etc. (iNematocera ana Bra- 



chycera) 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. Frontal lunule present; ptil- 

 inum usually present. Examples of this suborder are flesh 

 and horse flies, bots, drone flies, etc. Among these are but 

 few having aquatic larvae — a few Syi-phidae, some of the 

 Sciomyzidaei and other Acalj'ptrate Muscids ....Cyclorrhapha 



1 See N. Y. State Mus. Bui. 47. 1901. p.577. 



