136 DIPTEEA. 



27. Anthrax faustina, sp. n., <s ? . 



Male. Ground-colour of the whole body black. Face, cheeks, front immediately above the antennae and occipital 

 orbits densely beset with snow-white scaly hairs ; some scattered yellowish appressed hairs a little higher up 

 on the front ; the rest of the head with the usual black, erect pubescence ; antennae black ; face very little pro- 

 minent. The collar of hairs in front of the thorax and the long hair on the pleurae and chest of a pale whitish- 

 yellow; a short stripe of hairs above the root of the wings, and a tuft in front of them, whitish; a 

 cross-band of golden tomentum before the scutellar suture, but only a trace of such a tomentum at the 

 tip of the scutellum ; the tomentose covering of the surface of the thorax and of the scutellum consisting 

 of very delicate scales (very little conspicuous and perceptible under a lens only) of a dark metallic 

 brownish or greenish hue. Knob of the halteres infuscated. Abdomen : second segment with a narrow 

 cross-band of white hairs ; the following segments each with a narrow cross-band of fulvous scales, that 

 on the third segment occupying its anterior margin, those on the following segments being nearer the 

 posterior margins ; seventh segment entirely concealed under a thick covering of silvery scales. 

 Sides of the abdomen fringed with white hair, except on segments 3, 5, 6, which have tufts of black hairs 

 or rather scales. Venter with dense white pile, interrupted by narrow black stripes at the base of the 

 segments (these are less visible when the segments are contracted) ; the hairs or scales on the third and 

 the following segments sometimes pale yellowish or fulvous ; anus with a tuft of black hair. Legs 

 pale rufous, with the usual scaly covering ; knees and tarsi dark brown ; tips of the tibiae often infuscated. 

 Wings hyaline, including the costal cell ; the root only, before the basal cross-veins, yellowish-brown ; 

 costal enlargement clothed with bright fulvous scales, mixed with black ones. 



Female. Differs from the male in having the fringe of golden yellow appressed tomentum along the posterior 

 margin of the scutellum more distinct ; on the abdomen the second segment has a cross-band (narrower 

 in the middle than on the sides) of pale, almost whitish-yellow, tomentum anteriorly ; nearly the whole 

 of the fourth and sixth segments covered with a tomentum of the same shade of yellow ; a narrow 

 cross-band on the anterior part of the third segment, and another on the fifth, of a more saturate 

 yellow ; no silvery scales on the seventh segment, 



Length 10-11 millim. 



Hab. Mexico, Northern Sonora (Morrison). 



The description is drawn from unabraded specimens ; 1 had perhaps four or five such 

 out of twenty-six. In most of the examples the yellow cross-bands were more or less 

 abraded ; the white cross-band on the second segment of the male and the silvery scales 

 at the tip of the abdomen are, however, more persistent. The absence of a distinct border 

 of golden tomentum from the posterior margin of the scutellum of the male will also help 

 to distinguish this species ; in fresh specimens there is a trace of such a tomentum at the 

 tip of the scutellum only. The females are more difficult to separate from those A. sabina : 

 the cross-bands on segments 2 and 4 in the latter are narrower and of a purer white ; the 

 fringes of hair on the sides of segments 4-7, and especially the tufts of white hair on 

 segment 7, are shorter and less conspicuous. But both sexes of A. faustina will be 

 distinguishable from A. sabina by the infuscated knob of the halteres. 



The sides of the second segment of the abdomen are, as usual, rufous, as may be 

 seen in abraded specimens ; sometimes this colour extends to the first and third 

 segments. The legs are variable in colour ; black femora often occur ; as a rule, the 

 smaller the specimens, the darker the legs. 



The size given is taken from normal specimens; smaller ones sometimes occur. 

 Fifteen males and eleven females were sent by Mr, Morrison. 



