The Crane-Flies of New York — Part I 857 



almost vertical in position. The dorsal part of the postnotum lies between 

 the halteres, and the lateral part between the wings and the sciitellum 

 in front and the halteres and the metapleura behind. This region is 

 often erroneously considered as being the metanotum. 



The pleuron of the mesothorax (fig. 126, a) consists of the mesepister- 

 num and the mesepimeron. The mesepisternum is the plate making up 

 the anterior part of the pleuron. It is bounded caudad by the mesepim- 

 eron and ventrad by the mesosternum. Its dorso-cephalic angle is close 

 to the mesothoracic spiracle. The mesepimeron is the plate making up the 

 posterior part of the pleuron. It is a long sclerite, lying underneath 

 the wing base and bordered behind by the mesonotal postnotum and 

 the metepisternum. 



The sternum of the mesothorax is usually prominent, lying beneath 

 the pleura and bearing the middle legs. 



The mesothorax bears the wings of the insect, as well as the middle 

 legs. The details of the wing venation are discussed under a separate 

 caption (page 860). The wings are always present in crane-flies, but 

 they are very tiny and reduced in the genus Chionea, and in many genera 

 and species they are so reduced as to be useless for flight. This atrophy 

 of the wing may consist of a reduction in width only, the length being 

 unaffected and the organ taking on a straplike appearance (as in Tipula 

 pribilofensis) ; or there may be a reduction in both the length and the 

 width, the wing in extreme cases (such as Tipula chionoides, Platylimnobia, 

 and others) being a mere pad which is shorter than the halteres. As 

 a result of the distortion of the wing shape there is a corresponding reduction 

 and atrophy of the venation. In the northeastern United States and 

 eastern Canada, all the crane-flies are full-winged except the nearly wing- 

 less Chionea, mentioned above. 



The wing surface is usually provided with a microscopic pubescence, 

 to which are due many of the opalescent reflections in crane-flies (as in 

 Antocha, Dicranoptycha, and other genera). In addition to this micro- 

 scopic pubescence there is also found, in many scattered groups of genera, 

 a strong pubescence, which is apparent with a hand lens. The writer 

 regards the retention of this coarse pubescence as being a primitive char- 

 acter. Its nature varies. In some genera it covers the whole surface of 

 the wing — as in Ormosia, Ula, and Ulomorpha; in many species it is 

 confined to certain of the apical cells of the wings — as in Dicranomyia 



