VESTITURE. 



43 



Sixth longitudinal . 



Humeral cross-vein 



Anterior cross-vein . 



Posterior cross-vein 



Anterior basal or discal cross-vein 



Costal cell .... 



Subcostal cell .... 



Marginal cell .... 



First submarginal cell 



Second submarginal cell 



First basal cell . . , 



Second basal cell 



Anal cell ..... 



Axillary cell .... 



First posterior cell . 



Second posterior cell 



Third posterior cell 



Fourth posterior cell 



Fifth posterior cell . 



Discal cell 



IX Anal .... Anal 



(v) Basal cross-vein 



(w] Median cross-vein 



(x] Posterior cross-vein 



(y] Discoidal cross-vein 



2ndl Costal 



II .... Mediastinal 



III .... Subcostal 



1113 . . . First cubital 



1114 . . . Second cubital 

 2ndIII . . . First basal 



V ... Second basal 



VIII . . . . Third basal 



IX ... Axillary 



1115 . . . First posterior 



VI . . . Second posterior 

 2ndV2 . . Third posterior 

 \~3 . . . Fourth posterior 

 VIII . . . Fifth posterior 

 ist V2 Discoidal 



VESTITURE. 



Flies differ much in the nature of their vestiture. 

 Many are nearly or quite bare; others have a thick, 

 woolly covering of closely set, fine hair; while others 

 still are covered abundantly with a long, stout and heavy 

 bristles or macrochaetae. Doubtless the vestiture has an 

 intimate relation with the habits of the mature insect; 

 just what the relations of the different kinds are, is 

 not yet well understood. Osten Sacken has observed that 

 the eremochaetous kinds (that is those diptera in which 

 there is a general absence of bristles, as, for example, 

 the Stratiomyidae, Leptidae and Tabanidae) are, for the 

 most part, holoptic in the male sex, and at the same time 

 are chiefly aerial in habit, flying swiftly and often hov- 

 ering, using the legs only for alighting and resting. On 

 the contrary, the chaetophorous flies (as the Muscidae in 

 the wide sense, Phoridae, Dolichopodidae, Asilidae, etc.) 



