OuDJui 12. DIPTERA. C37 



general tlie pupipara; are destitute of ocelli ; the thorax is furnished witli four spiracles, two anterior 

 and two posterior; J^he latter pair, overlooked by Dufour, are situated, as in other Diptera, near the 

 base of the bala:iC3rs. The abdomen of //. ovina is furnished with ten spiracles, in the shape of 

 small, round, corneous tubercles, the four posterior being close to the anus. The wings are always 

 apart, and accompanied by balancers ; their [fore-edge] is more or less margined with setae ; the supe- 

 rior nerves, which are nearest it, are strong and well defined ; but those which extend to the hinder 

 edge are weak, and not transversely united. In the terminal Diptera of this family these organs 

 are wanting, or simply rudimental ; the balancers are also obsolete. The legs are terminated by two 

 robust claws, which have one or two teeth on the under side, which makes their appearance double 

 or triple. The covering of the abdomen is continuous, so that this part of the body can be distended, 

 and acquire a considerable volume, as becomes necessary in the body of the female Hippohosc<p, for 

 their larva; are hatched and are nourished therein until the period of their transformation into pupa;. 

 They are then discharged under the form of a soft, white egg, nearly as large as the abdomen of the 

 female ; the skin hardens, and becomes a solid cocoon, brown at first, but subsequently black ; round, 

 and often notched at one end, exhibiting a shiny plate or operculum, wliicli becomes detached like a 

 cap at the period of t\c final transformation. This cocoon has neither rings nor transverse incisions 

 by which it is di«^.»iguished from those of other Diptera, especially the Athericera, which it most 

 resembles. It is in the fine works of Reaumur, De Geer, Leon Dufour [and Lyonnet], illustrated as 

 they are by figures in detail, that we must look for a complete account of these transformations, and 

 of the changes which take place in the female at the period of her delivery. According to L. Dufour, 

 the ovaries in their configuration and position singularly resemble those of the human female. The 

 matrix, at first small, becomes enormously dilated, until it occupies the whole of the abdominal cavity. 



These Diptera are known under the name of Spider-flies, and live almost exclusively upon some 

 quadrupeds and birds. They run very quickly, and fly sideways. 



Some, or the Coriacea, Latr., have the head distinct, and articulated with the anterior extremity of 



the thorax. They form the genus 



Hippo BoscA, Linnaeus. 



Hippobosca proper, has wings, distinct eyes, and antenna: in the shape of tubercles, with three setJe on their 

 upper side. //. equina, Linn., the Horse- or Forest-fly, a species common in some places on Horses, which It 

 infests, especially fixin? itself in great numbers beneath the tail. 



OrnUhonvjia, Latr., has the antenuK in the shape of villose plates, and the nerves of the wings extending to 

 the liind edu;e. 



These insects form, in the monograph of Leach, four genera. 



Feronia {Nirmomyia, Nitzsch.), distinct by the antennae-like tubercles, and the claws of the tarsi double, atid 

 not treble. 



Ornithomyia, with ocelli and tridentate claws, pl.itc-like antennae, and wings of large size, and roimded. 



Stcnepteryx, similar to Feronia, but with very long acute wings. 



Oxi/plerum, with acute wings, but with the antenna; in the form of teeth, eyes small, ocelli wanting. Tliey live 

 on various species of Birds. Hippobosca avictdaiia, Linn. 



Strebla, Wied., has the wings incumbent on the body, with longitudinal nervures united by some transverse 

 nervures. The eyes are very small, and situated at the posterior angles of the head. Found on a South American 

 species of Bat. 



Melophagiis, Latr. (Melophila, Nitzsch.), destitute of wings, and with the eyes scarcely distinct. Hippobosca 

 ovina, [the common Sheep-tick]. 



A species of Melophagus, which lives on the Stag, exhibiting rudiments of wings, and with the thorax a little 

 larger than the head, forms the subgenus Lipoptciia, Xitzsch. Near jMclophagus ought also to come the genus 

 7ira«/ff, Nitzsch., of which the only known species lives on the Honey-bee, and is absolutely blind. Its thorax 

 is divided into two transverse parts, and the last joint of the tarsi is furnished with a row of small bristles. 

 Rdaumur had long ago figured this, or a closely-allied animal. 



The other Pupiparjc, Phthiromyiic, Latr., have the head vciT small, or almost obsolete, forming near 

 the anterior and dorsal extremity of the thorax a small body, which is elevated vertically. They 



compose the genus 



Nycterieia, Latr. (PMMridium, Hermann), — 

 And have neither wings nor balancers, and more nearly resemble Spiders than HippoboscK. They live on Bats. 

 Linnxus places the only species with wliich he was acquainted with the PedicuU. See the article Xyclcribia, in 

 the Enci/clopc'dic Meihodique, and in the Notiv. Diclionn. d'llist. NaltircUe, [and also my memoir in the Transac- 

 tions of l/ic Zoological f<ocic/j/ of London, in which I have described numerous species]. 



