768 Charles Paul Alexander 



erected, to include the generalized Tanyderina which have hitherto been 

 placed with the Ptychopteridae. 



The immature stages of the four families of the Tipuloidea are readily 

 separable. The larvae of the Tipulidae can be confused only with those 

 of certain low brachyccrous forms, as, for example, the Leptidae. In the 

 Brachycera the mandibles work vertically and parallel to each other; 

 in the Nematocera, including the Tipuloidea, they operate transversely 

 or obliquely against the teeth of the mentura and the hypopharynx. 

 The presence of fleshy lobes surrounding the spiracular disk is a character 

 possessed by almost all Tipulidae. The larvae of a few groups of brachyc- 

 erous Diptera, such as certain Leptidae, Sciomyzidae, and other families, 

 possess entirely similar caudal lobes but are readily recognized by the 

 small and very reduced head capsule. 



The eucephalous famiUes of the Tipuloidea may be distinguished by 

 means of the characters indicated in the following keys: 



Larvae 



1. Body eucephalous, head non-retractile; amphipneustic or metapneustic 2 



Head incomplete behind, retractile; not amphipneustic Tipulidae (p. 791) 



2. Caudal end of body prolonged into a slender breathing tube; metapneustic 3 



Caudal end of body not prolonged into a breathing tube; amphipneustic. 



Rhyphidae (p. 787) 



3. Breathing tube stouter, non-retractile; gills large, pinnately branched; punctures of head 



multisetose; found in wet decaying wood Tanyderidae, supp. (p. 769) 



Breathing tube slender, completely or partly retractile; gills slender, cylindrical, 

 unbranched; punctures of head with simple or plumose hairs; found in wet earth. 



Ptychoptebidae (p. 772) 



Pv-pae 



L One of the pronotal breathing horns greatly elongated, much longer than the body, the 



other breathing horn very short, abortive. (Family Ptychopteridae, p. 772) 2 



Breathing horns short, or, if elongated (some Tipulinae), not longer than the body 

 and the difference in size not so apparent 3 



2. Tarsal sheaths lying side by side, parallel Ptychopterinae (p. 773) 



The fore tarsal sheaths overlying the middle pair, the four middle and hind tarsi the 



longest, parallel Bittacomorphinae (p. 779) 



3. Tarsal sheaths overlying one another in pairs Rhyphidae (p. 787) 



Tarsal sheaths lying side by side Tipulidae (p. 791) 



The pupae of the Tanyderidae are still unknown. 



It is possible that Bittacomorphella (page 779) has short breathing 

 horns; in this case this genus would run down to couplet 3 above, but 

 by the arrangement of the tarsal sheaths it runs out as indicated in 

 couplet 2. 



