DIASPIN^ : MALE. 77 



hairs, the latter on the apical joint being frequently 

 knobbed (PL XXV, figs. 4 and 5). Four large promi- 

 nent ocelli are usually present, the upper pair (Fig. 

 12, a) placed just within the margin behind the 

 antennae ; the second pair, on the ventral surface con- 

 siderably within the margin, are not very widely 

 separated (Fig. 12, 1). The true eyes (Fig. 12, c), minute 

 colourless organs often difficult to trace, are placed 

 between the anterior margin of the genae and the large 

 dorsal ocelli. The genae (Fig. 12, d) are large, lobe- 

 shaped organs extended backwards, and overlap and 

 constrict the anterior margin of the thorax. The latter 

 is very large and occupies about one half of the whole 

 body; of its three component parts the prothorax 

 (Fig. 12, e) is less defined than the others; dorsallythe 

 mesothorax (Fig. 12, /) bears a broad chitinous band 

 (apodema, Fig. 12, g) at its posterior extremity, which 

 forms a conspicuous feature, as it generally has a 

 highly polished surface, and is often coloured darker 

 than the rest of the thorax ; on its ventral surface is 

 a broad scute, with a central division, widest in front, 

 sides and posterior margin continuously rounded. The 

 metathorax bears a large rounded triangular or shield- 

 shaped scutellum (Fig. 12, h), having a delicate epi- 

 dermis not highly chitinised. 



The single pair of wings attached to the mesothorax 

 are very narrow at the base, but gradually widen out 

 and have broadly rounded tips; they usually extend 

 beyond the stylus, but in a few species they are more 

 or less rudimentary. The lower pair of wings are 

 represented by halteres (Fig. 12, j), consisting of an 

 elongated tubercle bearing a stout-hooked bristle which 

 fits into a little upturned portion of the wings (Fig. 

 12, k). The legs are usually long, slender, and hairy; 

 have a single-jointed tarsus, with a simple claw and 

 from two to four knobbed hairs (digitules) ; they are 

 attached respectively to the pro-, meso- and metathorax. 



The abdomen, of nine segments, is often longitu- 

 dinally furrowed just within the margins; the anal 



