DIDYMA. 159 
the lateral portions; frontal bristles on each side in a curved row, descending as far as the end of the 
second antennal joint; the bristles on the vertex and two lateral ones more robust; central part of the 
face blackish, with white reflections; cheeks ochraceous, with brown reflections; eyes densely clothed 
with yellowish pile; bristles on the facial ridges mounting to half the face. Antenne black, shorter 
than the face; second joint with short bristles; third joint four times as long as the second; arista 
thickened at the base. Proboscis black, its terminal lips and the palpi dark rufous. Thorax and 
scutellum black; thoracic dorsum before the transverse suture with cinereous tomentum and four black 
stripes. Abdomen elongate-oval ; first segment black, shorter than the following segments, which are 
brownish-black with whitish front margins, the whitish colour interrupted in the middle and sometimes 
having the appearance of larger or smaller spots; discal and marginal macrochete are present, but the 
discal ones are shorter than the others. Legs black; middle tibiae with some long bristles; hind tibie 
outwardly with bristles of unequal length. Tegule yellowish. Wings greyish-hyaline ; small cross-vein 
distinctly before the middle of the discal cell ; apical cell very narrowly opened just before the wing's 
tip ; apical cross-vein straight ; posterior cross-vein curved. 
Hab. Mexico, Sierra de las Aguas Escondidas in Guerrero 9500 feet (H. H. Smith). 
One male example. 
A female specimen from Amula, 6000 feet, in Guerrero (H. H. Smith), agrees with 
the above description ; but it has the front broader, the tomentum on the thorax more 
extended posteriorly, the black stripes more distinct, the abdomen shorter and broader 
and with (in addition to the whitish front borders to the segments) irregular cinereous 
and black reflections, and the opening of the apical cell less narrow. It is probably 
the other sex. of D. ambulatriz. 
4, Didyma otiosa, sp. n., ¢. 
Blackish ; front and cheeks ochraceous ; thorax cinereous, with four black stripes; abdominal segments with 
whitish front borders ; macrochsete short. 
Length 6°5 millim. 
Allied to the preceding species (D. ambulatria), but differing from it in the following respects :—The pilosity 
of the eyes is much shorter and only conspicuous under a strong lens; the cinereous tomentum and the 
black stripes on the thorax are extended to behind the transverse suture ; the whitish front borders of 
the abdominal segments are more sharply delineated and there is a more distinct black dorsal stripe ; 
the discal and marginal macrochste are very short and but little conspicuous among the black hairs ; the 
apical cell is more broadly opened at its end. 
Hab. Mexico, Amula in Guerrero 6000 feet (H. H. Smith). 
A single female specimen. 
5. Didyma basilaris, sp. n., ¢. 
Black; head ochraceous; frontal band narrow; thoracic stripes indistinct; abdomen with whitish reflecting 
spots and with discal and marginal macrochete ; base of the wings infuscated. 
Length 5°5 millim. 
Front ochraceous, slightly prominent ; narrowed behind and there narrower than the eyes; frontal band black, 
linear ; frontal bristles descending as far as the end of the second antennal joint; face and cheeks 
ochraceous ; eyes densely clothed with yellowish pile; bristles on the facial ridges stout. Antenne black, 
nearly as long as the face; second joint with short bristly hairs; third joint five times as long as the 
second; arista thickened to its proximal half. Proboscis black; palpirufous. Thorax blackish, anteriorly 
with some cinereous tomentum and obsolete black stripes ; scutellum black. Abdomen ovate, black, with 
