882 DIPTERA. 



from transverse swellings on the under side of the body. 

 "The end of the body is truncated, and the two spiracles are 

 placed upon the truncature," from the edge of which part arise 

 usually four retractile processes. 



In the aquatic larva of Ptjxhoptera there is a long respira- 

 tory tube at the end of the body. The pupse (Fig. 299, under 

 \ I side, enlarged twice, represents a pupa of this family) 

 ^\ have usually on the thorax two horn-like processes, 

 MF/A J^'^Pi'esenting the thoracic spiracles, and in Ptj^choptera 

 uVr/l ^^^^ ^^ these processes acquires a great length, in order 

 I^Ji^ to allow the pupa to breath under water. 

 Xi^—^li The Tipulids, like other flies with soft bodies which 

 - ^^ contract in drying, should, as Osten Sacken suggests, 

 ^^S^ be studied from fresh specimens, especially when the 

 A/ thorax and abdomen, with the ovipositor, are to be ex- 

 Fig. 299. amined. The Tipulids of the United States, east of the 

 Mississippi river, closely represent those of Europe, while Os- 

 ten Sacken states that a few species are found to be common to 

 both countries ; and he farther states, with regard to the Tip- 

 uliclce, that "whenever the North American fauna differs from 

 the European in the occurrence of a peculiar generic form, or in 

 a marked prevalence of another, this difference is due, either to 

 an admixture of South American forms, or of forms peculiar 



to the amber fauna." 



y^l ^ ^ '^ — ^ — ^J^^^=^ The genus Tipula com- 



i^^.,,—,,;;;---^^^^^^^^ prises the largest individuals 



''vT^X^I^^^^^I^-'^'^/^ -'' of the family, and the species 



""" ^- ^— -" niav be seen earlj^ in May fl}- 



^'^' ^'^' ing over grassy fields. The 



larvjE live in garden mould and under moss in fields and woods. 

 T. trivittota Say is one of our most common species. 



In the genus Limnohia the body is very slender and delicate, 

 though stouter than in Dicranomyia, a closety allied genus, the 

 larvie of which are probably aquatic. "The larvae live in de- 

 caying vegetable matter, especially in wood and fungi." "Van 

 Roser discovered the larvae of the European L. annulns (closely 

 allied to L. cinctipes Sa}-) in decayed wood. Thej" are like an 

 earth-worm in size, as well as in color, and line their burrows 

 with a kind of silken web." (Osten Sacken.) 



