Gastrophilus. 77 



Vibrissal ridges bending angularly in below antennal fovea and 

 about meeting in the middle; then bending angularly down and 

 running close to each other to the mouth aperture, the middle part 

 of epistoma thiis forming a narrow keel between the ridges; the 

 whole epistoma broad, below the fovea confluent towards the sides 

 with jowls and intermediate triangle. The antennal fovea is placed 

 above, sharply bordered below, divided by a carina. No vibrissæ. 

 Eyes bare. Mouth parts rudimentary; small globular palpi are seen, 

 and between them a quite minute proboscis. Antennæ inserted at 

 the lower margin of the eye, more or less small, third joint globular 

 or somewhat lenticular; arista bare, thickened just at base. Thorax 

 quadratic, the transverse suture placed behind middle and inter- 

 rupted in the middle. No bristles on thorax and scutellum, no 

 sternopleural bristles either, and hypopleura bare. Abdomen shows 

 the first segment distinctly, it is triangularly produced backwards 

 in the middle; in the male abdomen is elongated oval, curved down- 

 wards towards apex. Genitalia small or larger, placed at the end; 

 arms of lower forceps more or less finger-like, curved towards each 

 other. Abdomen in female more elongate, sixth segment narrowed, 

 more or less elongated, seventh forming a shorter or longer ovi- 

 positor, with a pair of generally triangular lamellæ at end, an upper 

 and a lower; the ovipositor is bent forwards in under abdomen, 

 reaching to its base; in pecorum it is less bent in. Abdomen has no 

 bristles. Legs somewhat slender, without bristles; femora with long 

 hairs below and on posterior side, hind femora sometimes sparingly or 

 with none; tibiæ short-haired. Claws and pulvilli strong, of the same 

 or about the same size in both sexes. Wings with discai vein going 

 straight to the margin, thus no apical cross-vein; costa continued 

 only to cubital vein or a little beyond; posterior cross-vein placed 

 below or a little before medial cross-vein, or considerably behind it, 

 in some species wanting; anal vein reaching the margin; no bristles 

 at base of cubital vein; the wing-membrane corrugated. Squamulæ 

 rather small, the thoracai fringed at margin. 



The full-grown larva is cylindrical, somewhat flattened, pointed 

 anteriorly but cut behind. It has girdles of strong spines all round 

 on the segments except on the last or two last. On the head there 

 are two strong mouth hooks and between them a pair of small 

 triangular chitinous processes. The species are parasitic on horse, 

 living in the stomach, nasalis in duodenum; one species is recorded 

 from the ass. The eggs (pale in egui and nasalis, dark in pecorum 



