43 ^^ \ ^■■ 



FOURTH SOIREE. 



Friday Febi!L'auy 10, 1882. — House-Flies — W. H. Hakringto.v. 



A Paper descriptive of the appearance and habits of the Common House-fly 

 (Musca domestica), in its various stages. 



Os Some Canadian Ectoparasitic Sarcoptidje — J. B. Tyrrell, B.A. 



The species described in the following paper were collected by my brother' 

 Mr. H. E. Tyrrell, and myself, from some of our common Canadian birds. 



M.M. Ch. Kobiu and Meguin give the following general characters for the 

 Sarcoptidre :• 



" Animals greyish or reddish, very small (varying in length from one-tenth 

 of a millimetre to about a millimetre), body soft, without a dorsal shield, and without 

 eyes or respiratory stigmata ; with a rostrum provided with very small unarmed 

 jaws, carrying lateral, often large maxillary palps with three joints, furnished 

 with from one to three hairs, joined along a part of the inner border to a mem- 

 branous lip, which is shorter than the mandibles and carries two hairs on its 

 lower surface, and a lance-like little tongue on its upper. The five-jointed feet 

 arranged in two groups of two pairs each, placed, the one near the head, the other 

 after a considerable intervening space near the abdomen, the tarsus terminated 

 by a cup-like cushion furnished with claws, or by a sucker with or without a claw, 

 at least on the anterior feet, and these (suckers) may be pedicelled or not, though 

 they are wanting in the adult females of some species." 



The family above described includes among others the ectoparasitic forms of 

 which we are treating. They were originally included by Koch in his genus Der- 

 maleichus, which now, however, ranks as a sub-family, including some ten or 

 twelve genera within its bounds. 



We might here run over shortly the structure of the animals belonging to 

 this group. 



The general outline of the body is oval or oblong, more or less elongated, 

 with the rostrum projecting from the anterior end. This latter, as has been lately 

 shown by Dr. G. Haller f is composed of the following parts : an epistome, which 

 is simply a prolongation of the skin of the dorsal surface stretching forwaid and 

 bending downwards on each side, thus covering the other mouth-parts above and 

 on the sides. Beneath this are situated the triangular unarmed mandibles, which 

 project a little beyond the front of the epistome. Under, and stretching behind 

 the mandibles into the body cavity, are seen the first pair of maxilL-B, bearing on 

 their outer and upper side the three jointed palps. The rudimentary second pair 

 of maxilla? lie under the first, and under them lies the lower lip, sometimes con- 

 siderably extended. The alimentary canal commencing at the mouth runs back- 

 wards for a short distance, then dilates into quite a wide stomach, again contracts 

 and runs backwards as a rather narrow tube to open by an anus at the posterior 

 end of the body. Salivary glands are situated on each side of the oesophagus 

 and open by ducts into the front ot the gullet between the mandibles. Dr. 

 Haller considers that some of the cells of the stomach serve the purpose of a 

 liver, but otherwise no distinct liver has been detected. The nervous system 

 consists of a ga"glion situated above the O'sophagus, but up to the present I 

 have not been able to make out any nerves coming from it, though no doubt such 

 exist. 



* Journal de VAnat, 1877, p. 21.3. 



t Zeit. fir Wissen. ZooL, Band xxxvi. 



