DIPTERA. — HIPPOBOSCIDZ. 583 
organs, and I recollect no instance in the Diptera in which mandibles 
exist without maxillz, or maxilla without maxillary palpi. If we 
look at the usages of these organs, a very material variation must 
exist in the manner of taking the food; the rostriform plates must 
perform the office of the palpi in the other Dipterous families, to clear 
away the hair or feathers from the spot in which the long sete are to 
be thrust; the largest of which seta forms a canal for the ascent 
of the nutritive fluids into the pharynx. In the other Diptera, this 
is effected by the assistance of the large fleshy labial lobes, acting as 
suckers to draw these fluids to the surface of the skin; but here these 
are wanting, and consequently there can be no suction; but this is 
easily accounted for, from the great length of the internal sete, which 
must penetrate far deeper than those of the other Diptera, excepting 
those of the Gnat, in which, owing to this peculiarity, the labial lobes 
are very slightly developed. 
These insects are of small size, and much clothed with bristles, and 
have been termed by French authors, Spider-flies; they reside upon 
quadrupeds and birds, running with great agility, and often sideways, 
and burying themselves amongst the hair or feathers. The body is 
short and depressed, covered with a tough leathery skin. Latreille 
lays it down as arule, that the Pupipara are destitute of ocelli, but 
this is not the case; none exist in Hippobosca ; in Craterina they are 
very obscure, and sunk in 3 minute foveolz, but in Ornithomyia they 
are quite distinct, as Dufour observed: the thorax is dilated behind, 
having 2 spiracles on each side ; Latreille has discovered the posterior 
pair in the forest fly (Hippobosca), which Dufour had overlooked, 
situated near the base of the balancers. Curtis, also observed 4 in 
Stenepteryx. Latreille described 10 spiracles in the abdomen of the 
sheep tick (Melophagus), but Lyonnett, with still greater precision, 
discovered two pairs of thoracic, and seven pairs of abdominal spiracles 
in the last named insect. ‘The wings, when present, are either in- 
cumbent, or divaricate, and are always accompanied by balancers ; 
the apical nervures of the former in some species are very indistinct, 
(fig. 133. 6. wing of Hipp. equina; 13. wing of Stenepteryx Hirun- 
trompe de la puce,” (R. An. tom. v. p. 539.); that is, the maxillw, in which view 
of the subject the large lateral lobes of the mouth in thege insects would neces- 
sarily represent maxillary palpi. Mr. Curtis has figured these “ petites piéces,” in 
Ornithomyia, as anterior lobes of the mentum, and Mr, Newport, in Ozypterum, as 
undeveloped mandibles, 
