62 GROUSE. ["1899 



H. equina, will be much better conveyed by comparison of the two 

 plates than by description. The pads, or puhilli, and the very long 

 hairy bristle {enipoiliKm),* are present in each case ; but from differ- 

 ences in microscopic setting the details are in some respects more 

 clearly displayed in the figure of Ondthomijia. In regard to the pads, 

 of which both are well shown in Omithomyia, although from an un- 

 avoidable circumstance one only is given in Hippohosca, and also the 

 bristly empoillitm, I believe there can be no doubt ; but besides these, 

 both in the Grouse and the Horse Forest Fly, there is a sort of flat 

 flap placed apparently above and between the two claws, with lines 

 radiating from the centre to each side, — this is largest in the Forest 

 Fly's foot, — and there appears to be clearly connected with a bulb-like 

 process (see plates). Probably dipterists may be perfectly well acquainted 

 with this organ, but, as I have not been able to find any description 

 which seems to correspond with it, I merely give the figures.! 



The Grouse Fly [Omithomyia avicularia, Linn.) belongs, as above 

 mentioned, to the family HippohuscidcB, of the great division of Pupipara, 

 of which some are known as Leathery Flies [Corincea, Meig.), and some 

 (popularly with us) as Forest Flies. This genus may be distinguished 

 by the following characteristics from the others of the Hippoboscidm. 

 It possesses three ocelli ; it has on each foot two claws, of which each 

 claw is three-parted ; and also the wings, which are of the ordinary 

 proportion of ividth, are longer than the abdomen. 



Thus Omithomyia is distlntjuishable : — 



From Hippobosca (parasitical on horses and cattle), which has 

 no ocelli. 



From Otfersia (parasitical on birds), which has also no ocelli. 



From Stenopteryx (parasitical on swallows), of which the wings are 

 very narrow, being scarcely more in width than one-sixth of 

 their length, and are pointed at the extremity. 



From Oxypterum (parasitical on swallows), which much resembles 

 Stenopteryx, but has no ocelli. 



From Lipoptera { = Lipo2)tcna) (parasitical on deer), which has tivo- 

 parted claws. 



From Melophagus (parasitical on sheep), which is wingless, and 

 has no ocelli. 



From Braula (parasitical on bees), a very small kind, which is 

 wingless and also eyeless, and without perceptible ocelli. 



* " Pulvilli . . . are membranous pads, one beneath each tarsal claw; . . . 

 the empodium often exists between the two pulvilli of each tarsus. The empodia 

 may be bristle-like, or tapering, or membranous, resembling the pulvilli inform." — 

 ' Manual for Study of Insects,' p. 420, chap. xix. (Diptera), by John Henry and 

 Anna Botsford Comstrock. Ithaca, N.Y., U.S.A. 



t In my Nineteenth Annual Eeport I have entered in much detail on the life- 

 history and peculiarities of structure of various species of Hippoboscidce, with very 

 full references to the writers cited, pp. 95-118. 



