HARDWICKE'S SCIENCE-GOSSIP. 



157 



mouth alone, as mentioned before, it may be deter- 

 mined whether or no a fly belongs to the family 

 Asilidce. 



Besides the joining of the sub-costal and 

 radial veins already noticed, there is in the 

 wings of the genus Asilus another and con- 

 spicuous feature by which an asilus may be 

 known almost at a glance, namely, that one 

 of the externo-medial veins {em, fig. 87) 

 instead of going straight to the margin, 

 turns backwards and joins the post-brachial 

 (po). 



The legs of all the AsUidce are extremely Fi &- 9° 



caught. Except in the genus Leptogaster, the pads 

 are largely developed. The tenent hairs 



are 



Antennae : a of L. cylindricus, and//, of A. sestivus, x 50 diam. 

 Side view (seen from above the third of each is thin). 



long and straight; and if any one 

 still doubts whether in walking the 

 pads of a fly's foot adhere by suction 

 or by means of a viscous secretion, 



Fig. 88. Mouth of Asilus <pstivus, x 45 diams. Ibr, labrum ; I, lingua ; 

 la, labium ; mx, maxillae. The maxillary palpi are not lettered. 



Fig. 91, Tarsus of Zeptogaster cylindricus, 

 x 16 diam. 



he may be convinced that the latter is 

 the case, both by a microscopical'exa- 

 mination of the tenent hairs on the 

 pads of A. crabroniformis, and by 

 applying a needle to the foot of a 

 freshly - killed specimen, when they 



Fig.: 



Leptogaster cylindricus, male, clinging to a 

 stem. Magnified 2j diameters. 



Fig. 92. Head of Dioctria rufipes, x 14 diams. a, side view ; 

 b, top view j e, great eyes ; oc, ocelli. 



stout and muscular, being adapted for the seizure of 

 prey. They are covered with stiff bristles, probably for 

 the purpose of giving a firm hold of the prey when 



will immediately adhere. Suction would require a 

 muscular effort, which could not occur after death. 

 Asili, in fact if not in appearance, have three pads, 



