160 DIPTERA. 
whitish reflecting spots on the front borders of the second and following segments; densely beset with 
black hairs and armed with rather long discal and marginal macrochete. Legs black; middle tibie 
with some long bristles ; hind tibie outwardly with bristles of unequal length. Tegule yellowish-white. 
Wings greyish-hyaline ; the brownish tint at the base extended to the end of the first vein and over the 
three basal cells; at the base of the mediastinal cell is a hyaline point; small cross-vein a little before 
the middle of the discal cell; apical cross-vein oblique and straight; posterior cross-vein slightly 
curved. 
Hab. Mzxico, Omilteme in Guerrero 8000 feet (H. H. Smith). 
A single male specimen. 
6. Didyma modesta, sp. n., 2. 
Blackish ; head yellowish ; thorax cinereous, with four black stripes ; abdomen with whitish reflecting spots 
and with discal and marginal macrochete ; palpi rufous. 
Length 5°5 millim, 
Front a little broader than the eyes, with parallel sides; frontal band black, narrower than the lateral 
portions ; frontal bristles descending as far as the end of the second antennal joint; face and cheeks 
yellowish; eyes thinly pilose. Antenne black; second joint bristly ; third joint four times as long as 
the second ; arista thickened at the base. Proboscis black ; palpi pale rufous, slightly thickened towards 
the tip. Thorax and scutellum greyish-cinereous; thoracic dorsum with four distinct, rather broad, 
black stripes, the outer stripes interrupted at the transverse suture. Abdomen ovate, black, with whitish 
reflecting spots on the front borders of the second and following segments; discal and marginal macro- 
cheetes are present. Legs black; front tibie with a row of short bristles; middle tibie with some long 
bristles ; hind tibie outwardly with short bristles and a longer one below the middle. Tegule whitish. 
Wings greyish-hyaline ; small cross-vein a little before the middle of the discal cell; apical cross-vein 
straight ; posterior cross-vein very slightly curved. 
Hab. Mextco, Sierra de las Aguas Escondidas in Guerrero 9500 feet (H. H. Smith). 
A single female specimen. 
7. Didyma exigua, sp. n. (<2). 
Blackish ; thorax with indistinct stripes; abdomen with whitish front borders to the segments, laterally 
yellowish ; discal and marginal macrochete present. 
Length 4°5 millim. 
Front narrower than the eyes, almost wholly occupied by the black frontal band, the lateral portions linear 
and with a greyish reflection ; frontal bristles descending as far as the end of the second antennal joint ; 
face and cheeks blackish, the cheeks narrow; the inner orbits of the eyes grey; eyes thinly pilose. 
Antenne black; third joint four times as long as the second; arista thickened to its proximal third. 
Proboscis and palpi retracted in the oral cavity, apparently black. Thorax and scutellum black; thoracic 
dorsum anteriorly with some greyish tomentum and obsolete stripes. Abdomen obconical, shining black, 
the front borders of the second and following segments whitish, the second and third segments laterally 
yellow and somewhat transparent; ventral surface yellowish, with black hind borders to the segments and 
a black median stripe. Legs black; middle tibie with some long bristles; hind tibis outwardly with a 
row of shorter bristles. Tegule yellowish-white. Wings greyish-hyaline; small cross-vein on the 
middle of the discal cell; third vein curved upwards before its end; apical cell very narrowly opened 
just before the wing’s tip ; apical cross-vein slightly concave; posterior cross-vein distinctly curved. 
Hab. Muxico, La Venta in Guerrero 300 feet (H. H. Smith). 
A single specimen, which, owing to the narrow front, seems to be a male. 
