ON A PARASITIC DROSOPHILA FROM TRINIDAD. 161 



The wings have the form and venation shown in fig. 4. The lower cross-vein is 

 broadly clouded as indicated by the dotted lines. A darkened area extends from 

 the costa across to the third vein, the approximate boundary of its darkest part 

 being shown by dots ; the darkening then quickly shades off into the greyish glassy 

 surface of the rest of the wing. The basal segment of the costa is well bristled, the 

 last bristle at the costal break being the strongest. 



The abdomen is yellow and slightly shining, the last two segments being darkened 

 with ill-defined borders extending broadly along the hind margins of the segments. 

 The dorsum is covered with small bristles somewhat converging towards the 

 axial line ; the marginal bristles, about 4 on each side, are considerably longer 

 and stouter and more regularly spaced. The hypopygial segments are somewhat 

 darkened and hairy ; all that is externally visible is a small terminal knob and what 

 are possibly the tips of the side appendages ; the whole apparatus gives one the 

 impression of its being a small edition of the type of thing seen in Leucophenga 

 maculata. 



Fig. 4. Wing of Drosophila paradoxa, x 30. 



?. A very careful comparison was made by viewing the specimen in conjunction 

 with the camera lucida drawings made of the male. There is practically no 

 structural difference of any weight to be found. The lower hind quadrant of the 

 eye boundary in side view is somewhat less rounded, but that is a matter that varies 

 to some extent in a single species, giving a more or less pointed appearance to the 

 lower part of the eye. A long series of D. melanogaster will show quite perceptible 

 differences in this respect. The chaetotaxy, both cephalic and thoracic, and the 

 relative size of the bristles are the same, as are the legs. The wings have exactly the 

 same venation and relative positions of all the veins, but are very slightly shorter. 

 The main difference is in the colour of the wings ; the suffusion is almost absent, but 

 can just be seen in a proper light. The peculiar structure of the abdomen has been 

 described on p. 157. The central hairy ridge is pale yellow on its base. The last 

 segments are more darkened, and the terminal one bears a crown of regularly 

 spaced bordering bristles, which are stout and very nearly as long as the previous 

 segment. 



Length, just under 2 mm. ; wing, the same. 



Trinidad : St. Joseph, 3 specimens, xii. 1917 (C. B. Williams). 



The single female from Panama is superficially very like that of the last species. 

 The side view of the head is much the same, but it is not quite so high in proportion 

 to its breadth, and the jowls are a little narrower. The inner row of aristal rays 

 is very evident. The thorax was spoiled in pinning, but as far as can be seen the 

 chaetotaxy is the same, as is that of the head, though the bristles are less stout. 



