DIPT ERA. 383 



comes a firm shell, at first brown, then black, round, and frequently 

 cmarginated at one end, and jtresenting a glossy plate or operculum 

 which is finally detached in the manner of a cap, to allow the egress 

 of the perfect Insect. This shell has no annuli or transverse inci- 

 sures, a character which distinguishes it from the other pupae of 

 Diptera, and from those of the Athericera particularly, to which it 

 approximates the most. 



It is to the splendid Memoirs relative to these Insects by Reau- 

 mur, De Geer, and M. Leon Dufour, all accompanied by detailed 

 figures, that we must recur, in order to obtain a profound knowledge 

 of tliese transformations, and an explanation of the changes which 

 take place in the female at the moment of depositing her larvae. 

 The latter, in particular, has surpassed his predecessors by anatomi- 

 cal investigations which have unveiled some highly interesting and 

 curious facts, such as the existence of salivary glands, of a sort of 

 matrix* consisting of a large, musculo- membranous pouch, adapted 

 for gestation and analogous to the uterus of woman, and of ovaries 

 entirely different from those of other Insects. These ovaries consist 

 of two obtuse, ovoid bodies filled with a white homogeneous pulp 

 free and rounded at one extremity and terminating at the other in 

 a peculiar duct. According to this anatomist these ovaries closely 

 approximate to those of woman in their form and position ; Reau- 

 mur had a glimpse of them. The matrix, which at first is very small, 

 by the progress of gestation becomes enormously dilated, pushes back 

 the viscera, and finally invades the whole cavity of the abdomen, 

 which is thus rendered very large. The memoir of this able obser- 

 ver presents other interesting facts, which, as they differ but little, if 

 at all, from the ordinary laws, we shall not stop to analyze. 



These Insects, which have been called by some authors Mouches- 

 Araignees, live exclusively on Quadrupeds or Birds, run very fast, 

 and frequently sideways. 



Some — Cortaces, Lat. f — have a very distinct head articulated 

 with the anterior extremity of the thorax. They form the genus 



HiPPOBOSCA, Lin., Fab. 

 HiPPOBoscA, proper. 

 Furnished with wings; very distinct eyes occupying all the sides 

 of the head ; antennse in the form of tubercles, with three setje on the 

 back. 



* Professor Nitzsch, who, in his Memoir on Epizoic Insects, treats of various 

 genera of Pupipara, mentions two ovaries and four biliary vessels in Hippobosca, 

 but he neither alludes to this matrix nor to the salivary glands. 



t Dr. Leach has published a Monograph of these Insects, enriched with excellent 

 figures, beautifully engraved. 



