312' DIPTERA OF NORTH AMERICA. [PART IV. 



second submarginal cell ; it is much weaker in P. contaminata 

 and in the North American P. rufocincta. 



The venation of the three species which I have seen (P. albi- 

 mana, contaminata, rufocincta) is pretty much the same ; only 

 in P. albimana the praefurca is shorter and the first submarginal 

 cell is not sessile, but has a short petiole. The American P. 

 rufocincta has also a very short praefurca. 



Mr. Westwood (Introd. II, p. 526) was the first to call atten- 

 tion to a singular organ in the shape of a membranaceous, spatu- 

 late, small appendage, ciliated on the margin (Westw., 1. c, 

 fig. 126, 1), and inserted at the foot of the halteres of Ptychop- 

 iera. I notice the same appendage in Bittacomorpha, but none 

 in Protoplasa. Its use or homology is unknown ; it has nothing 

 in common with the tegulse, which are usually inserted more in 

 front of the halteres. 



Five European species are known ; a sixth, P. pectinata Macq. 

 (Hist. Nat. Dipt. I, It), from the North of France, is distinguished 

 by the antennae being pectinated, as in Ctenophora. It seems 

 to be very rare ; Mr. Rondani introduced for it the new genus 

 Ctenoceria. The American species, P. rufocincta, is quite 

 common. I have never found P. i-fasciata Say (Long's Exped. 

 etc. p. 359), also described by Wiedemann ; nor P. metallica 

 Walker (List, etc. I, p. 80), from Hudson's Bay. No Pty chop- 

 terse from any other part of the world seem to have been 

 published. 



The insects of this genus are found in the vicinity of stagnant 

 waters, where their larvae live. The larvae and pupae have very 

 early attracted the attention of naturalists, and have been often 

 figured (Reaumur, Mem. Yol. V ; Lyonnet, (Euvres posthumes, 

 Tab. XVIII, fig. 1-1 ; Van der Wulp, Handel. Nederl. Entom. 

 Ver. I, 1, p. 31 ; Lacordaire, Introd. a VEntom. Tab. II, fig. 5 ; 

 Tab. V, fig. 20, gives a copy of Lyonnet's figure). The larvae 

 have a long tube at the end of the body, which they raise to the 

 surface of the water for breathing. In the pupae, one of the 

 horny processes, which distinguish the thorax of all the pupae of 

 Tipulidse, is enormously prolonged, likewise for the purpose of 

 breathing under water (compare p. 10). 



The genus Ptychoptera (from ntvx^ fold, and rtttpbv, wing) has 

 been introduced by Meigen, in 1803 (IUiger's Magazin, II, p. 

 262). 



