GASTROrHILTTS. 397 



Genotypk, (Estrns equi, Clark ; by designation of Curtis. 



Head rnthev short, sometimes distinctly narrower than thorax, 

 seniiglol)ul:ir, vessiculose; cheeks putted up, thinly haired; eyes 

 rather .small, hare, wide apart in both sexes : t'rons generally with 

 a median impresstd line ; three distinct ocelli ; antenna? seated in 

 a single heart-sh;iped cavity, bisected by a median ridge; first two 

 joints very small, 3rd oval, compressed, projecting heyond the 

 cavity, arista dorsal, bare; mouth-opening small, rounded; pro- 

 boscis A-ery rudimentary ; palpi small, short, globular; a median 

 impressed line extends from the antenual cavity to the mouth- 

 opening. Thorax oval, short, gently curved ; thoracal squan)a3 

 small, long-liaired. Abdomen variously shaped, genei'ally oval or 

 subconical ; in some species much broader than thorax. Genitalia 

 in J inc()nspicuou8, in $ sometimes small, generally prominent, 

 elongate, often conspicuously so, curved under the alxlomen, 

 differing in shape and size according to the species ; apical part of 

 ovipositor cylindrical, grooved on upper side. Legs moderately 

 long, comparatively slender ; pnlvilli large, claws slender. Wings 

 with characteristic venation ; 4th longitudinal vein nearly reaching 

 border of wing, quite straight; 1st posterior cell widely open; 

 discal cell as long as or hardly longer than anterior basal cell, in 

 some species open ; anal cell short. 



liani/e. Europe, Asia, Africa and America. 



Life-histor)/. The larva lives in the stomach of the horse or other 

 EQUiD.i:, passing out with the dung when mature and pupating in 

 the ground, under stones or in holes in the earth ; the insects live 

 some months in the larval stage; the pupa takes the form of a 

 contracted larva. The larva is pointed at the front eiul ; the 1st 

 (cephalic') segment is provided with two large moutli-hooks ; the 

 3rd to the 12th segments possess rows of spines or hristles on 

 the front borders. The perfect insects are sometiuu^s found in 

 mnnhers on bare mountain-tops, or in high towers or trees, but 

 are usually unconimon ; they are usually moderately or densely 

 pubescent, furry species and are, especially in the hot sun, very 

 rapid on tlie wing. 



(J. tqui is easily known by the smoky band, sometimes in- 

 distinct, across the middle of the wings, which in G. nasalis are 

 quite clear. G. pecorum may be distinguished by having the discal 

 cell wide open, this cell being closed in tlie other two species. 



308. Gastrophilus equi, cJarl-. (PI. VI, (ig. 14.) 



Q^dnts equi, Clark, Trans. Liim. Soc. Lond. iii, p. l.'2(i, pl. xxiii, 



tips. 7-!) (1797). 

 CEKh-iis hovis, LinnaRus, Faun. 8hhc. ii, p. 1730 (17fil). 

 (Estruii {utestinalis. He (Jeer, Ins. vi, p. 291.1)1. xv,li^.s. l.'^-19 (1770). 

 Giatrns hfcmorvJwidalis, Gnielin (nee Linnajus), Sv.st. Nat. v, p. L'HIO 



(1788). 

 (lutnis giisfn'ctis, Srlnvnl), Die (Ivstrnciden, p. .31 (1840). 

 ^ (E^tnis tnitifo/x's, Palhis, Itin. i, App. p. 47o (1779). 

 Ct^trics bewjalensis, Macqnart, Dipt. Exol. ii, i)ait 3, p. L'5 (1843). 



