326 PERCY SLADEN TRUST EXPEDITION 
24. Drosophila sericea, n. sp. (Fig. 14 and Plate 19, fig. 12). 
A very handsome species in which the male has a very silvery thorax. 
$ Head. Eyes bare, red. Top view :—Frons nearly parallel-sided from the vertex 
downwards, a little over one-fifth of maximum axial breadth from eye to eye: creamy 
white; the area within the ocelli is grey with silvery reflections: ocelli bright red. The 
pair of lower f. 0. are inserted nearly midway on the frons and point forward: the first 
pair of outer backwards-pointing f. o. are inserted nearly level with the former, the second 
pair roughly midway between them and the vertical bristles. These f. 0. bristles are lower 
down the eye-margins than in the European species L. maculata: approximated 1. v., diy. 
o. v.; a small pair of deeply crossed p. v. b., stout oc. ; a row of minute crossed bristles on the 
centre of the frons; a row of similar bristles below front f. 0., so that it can be looked on as 
a continuous row of fine orbitals. Front view :—Face coloured as frons, slightly diverging 
to insertion of vibrissze, practically flat in section, a strong pair of vibrisse. Side view 
(Plate 19, fig. 12) :—Back of head darkish grey ; the post orb. continuous round mouth- 
margin; a stout bristle on lower hind angle of jowl. Antenne with the just visible 
first joint and the second joint coloured like the frons, slightly bristled, second with one 
longer outer dorsal b.; third joint parallel-sided with rounded tip, finely pubescent, 
slightly darkened ; arista pale for first half, then darker: six upper rays, three lower rays 
(1st near middle), terminal ray: on the under face of the plane of the arista is a row 
of tiny rays, denser for the proximal third and then extending more sparsely to nearly 
the end*. 
Palpi blackened and shining, tongue yellow, rugose at the tip: the mouth opening in 
vertical view is long and narrow, and the margin is blackened laterally. 
The thorax and scutellum are both brilliantly silvery in good specimens, the 
ground colour beneath being orange; the dorsal surface is covered with small bristles. 
There are two d.c., the front pair the smaller, small prescut., one h. and a few smaller 
bristles on humeri, two n. p., three bristles over wing, the p. a. large. The small 
thoracic bristles can be looked on as forming 8 or 10 acr. rows between the d. «. 
lines. Scutellum slightly arched, almost circular in profile, quite bare, with two large 
side bristles on large grey ill-defined spots, and two stout crossed terminals. Pleura 
somewhat orange-yellow with a darkened irregular stripe from the metanotum to the 
sternopleura. Two large st. p. Wings as Fig. 14, veins brown, the costa darker: the latter 
extends to 38rd: a fine dense black short bristly ciliation extends to about half-way 
between the ends of 2 and 3; it here becomes sparser, and between that termination 
and the end of 3 are four or five minute black tubercles inserted just on the lower 
edge of the costa. In macroscopic view the costal margin is distinctly infuscate. 
Halters with white knobs, and yellowed stalks. Legs entirely pale yellow-white 
except that the mid and hind knees are narrowly darkened. The usual preapicals 
* This inner row of small rays is a useful character: it varies in strength of ray, and in number, and 
is occasionally quite absent. It is plainly visible in Z. maculata. It will likewise be found in other insects: 
for example, in Lonchea plumata (see last paper, Trans. Linn. Soc., Vol. xv, Part 3, 1912, p. 303) it is 
almost as strong and evident as the upper and lower rows and is complete from end to end. 
