2 DIPTERA OP NORTH AMERICA. [PART IV. 



lipes and Toxorrhina (Tab. I, f. 6) have only nine veins, the 

 obliteration of a vein is in both cases evident). The Culicidse 

 and Psychodidse come next to the Tipulidse with regard to the 

 completeness of the venation ; but they have no discal cell ; among 

 all the other Diptera nemocera, this cell occurs only in Rhyphus. 

 The size and structure of the ovipositor, with its two pairs of 

 long, horny, pointed valves, is common, with very rare exceptions, 

 to all the Tipulidse (the ovipositor of the other Diptera nemocera 

 generally consists of two hardly projecting inconspicuous valvules). 

 The only genera exceptional in this respect are Cryptolabis and 

 Bittacomorpha ; their ovipositors do not show any horny append- 

 ages. 1 



These three leading characters of the Tipulidse — thoracic suture, 

 venation, and the structure of the ovipositor — sufficiently isolate 

 this family among the other Diptera nemocera ; but we render 

 the contrast still more striking, if we direct our attention to the 

 different parts of the organization of the Tipulidse, and compare 

 them with the corresponding parts in other families. Thus the eyes 

 here are rounded or oval, and never excised on the inside (reni- 

 form or lunate), like those of most Culicidse, Chironomidse, 

 Psychodidse, Simulidse, and some Mycetophilidse. The ocelli 

 are, with rare exceptions {Trichocera and perhaps Pedicia), 

 wanting, or, at least, imperceptible ; and this character the Tipu- 

 lidse share with the Culicidse, Chironomidse, Psychodidse, Simu- 

 lidse, and a part of the Cecidomyidse. The joints of the antennal 

 flagellum are, with rare exceptions, well marked in their divisions, 

 the shape of the whole antenna being in most cases setaceous, 

 that is, gradually attenuated towards the tip. The joints are 

 never absolutely cylindrical, as in some Cecidomyise (Asfthon- 

 dylia, Spaniocera), or of the compressed disciform shape, so 

 common among the Mycetophilidse ; only Rhipidia has them 

 pedicelled (a character common among the Cecidomyise). The 

 antennal joints are in most cases verticillate (a character very 

 rare among the Mycetophilidse) ; never bushy (a character of 

 general occurrence among the males of the Chironomidse and 

 Culicidse). With regard to the number of antennal joints, the 

 Tipulidse do not differ much from the other Nemocera; the 



1 I have neglected the opportunities I have had to examine the ovipositor 

 of Bittacomorpha on fresh specimens ; in dry ones, I perceive only a pair 

 of short, coriaceous appendages. 



