1920] Seamans: Anatomy of Anthomyia 211 



Though they appear to be rudimentary wings they are far 

 from being vestigial organs. There are three parts, the scabel- 

 lum (scm), or base, the scape or stalk (see), and the head (hd) 

 or the apical end (Fig. 11). The halteres are considered to be 

 auditory organs and they carry a fluid in canals similar to the 

 semi-circular canal of the higher animals, giving them the 

 function of maintaining equilibrium. 



The three pairs of legs are similar in structure and show 

 slight sex differences. The main difference, which appears in all 

 the legs, is that the bristles and spines of the male are stronger 

 than those of the female. For the purposes of this paper, the 

 legs will be spoken of as if they were drawn out at right angles 

 to the body (Fig. 30). The surface which is then directed for- 

 ward will be the anterior surface and opposite to it, the posterior 

 surface. That surface which is above will be the dorsal surface 

 and that opposite, the ventral surface. 



In the prothoracic legs (Fig. 30A) the coxa (ex) in both 

 sexes is longer than wide, of a somewhat irregular shape, and 

 equipped with five stout spines on the dorsal or flexor surface. 

 (Fig. 21 A). The trochanter is small, somewhat triangular, and 

 has no spines, and only one or two small hairs. (Fig. 24A and B). 

 The femur (fm) of the male differs from that of the female in 

 being strongly bowed. In both sexes this segment tapers 

 slightly towards each end, and is armed with rows of strong 

 ■ spines on the posterior surface, two rows especially on the 

 dorsal and ventral margins of the posterior surface (Fig. 28A). 

 The anterior Surface of the femur has a few irregular rows of 

 small hairs. The tibia (ti) is as long as the femur, small at the 

 base and slightly enlarged at the apex. (Fig. 31). In both sexes 

 the tibia is armed with a pre-apical bristle and an apical spur. 

 The tarsi (ts) are five-jointed (Fig. 36), the first being the 

 longest and equipped with a distinct spine at its base and 

 smaller ones below that on the ventral surface. (Fig. 36B). 

 All the tarsal joints are pubescent and each of the first four 

 has a weak apical spur (Fig. 36B). The fifth tarsal joint bears 

 two stout, simple claws (clw), tw^o pulvilli (pv), which are 

 larger in the male than in the female (Fig. 34A and B), and a 

 fine hair-Hke empodium (emp) (Figs. 35 and 36B and C). The 

 tarsi of all three pairs of legs are similar, having no distinct 

 differences. The pulvilli are membranous and covered with 

 long, fine hairs which arise from conical protuberances on the 



