ENTOMOLOGY ACARI. 401 



consisting of a very delicate membrane, and under eacli a sort of globular 

 reservoir composed of a network like that of Trombidia. These observa- 

 tions deserve every attention. The author's inferences seem pushed too far, 

 when lie assigns the function of expiration alone to the trachea! system of 

 the Trombidia. A similar system exists also in a number of spiders, along 

 with pulmonary sacs, which can scarcely be the direct recipients of the air 

 inspired. In the Phalangia the structure is similar to that in Trombidium, 

 &c., the main trunks of the tracheae having only their single orifices ; and 

 even in insects where the spiracles are multiplied, as each supplies a deter- 

 minate portion of the body with air-vessels, the spiracle must serve both 

 for inspiration and expiration. 



The natural liistory of our indigenous mites has received important illus- 

 trations from Koch, who has figured a number of species in the continua- 

 tion of Panzer's Fauna (pts. 183, 187, 188, 189, corresponding to pts. 33, 37, 

 38, 39, of Koch's Deutschlands Crustaceen, Myriapodeu und Araclmideu). 

 As the species have been already given in systemat ic order by the author in 

 his concise Uebersicht des Arachnideusystems, I refer the reader to that 

 indispensable work. 



Miescher (Bericht. Verhandl. Naturf. Gesellsch. in Basel v, 1843, p. 

 183) has given some details respecting mites in living animals. Nitzsch 

 had previously described some cases of this nature, as Sarcoptes nidulans, 

 which lives under the skin of Friugilla chloris in nests forming little lumps 

 with a small opening from the outside, and Sarcoptes subcutaneus, which 

 lives in the air-cells under the skin of the gannet (Dysporus bassanus). 

 The author discovered also in the air-cells of the ventral cavity, of the 

 bronchiee and tracheae, of the swift (Cypselus apus), a species of mite, accord- 

 ing to his description clearly a Sarcoptes (Dermaleichus, Koch), and 

 another species in the air-pouches of the ventral and pectoral cavities, in the 

 lungs and windpipe, of the great Butcherbird (Lanius excubitor), and this in 

 such abundance in the lower part of the tracheae and the brouchise, that 

 they actually filled the bore of these. Also in the common mouse, having 

 stripped the skin off, he found on its inner surface little milk-white knots as 

 large as a pin's head, or larger, which under the microscope appeared to be 

 nests of mites, containing from twenty to thirty little mites, lying in a com- 

 mon cavity composed of a delicate membrane without any aperture. In the 

 cellular tissue under the skin of the fox also, he has several times met with 

 larger mites (!'" in length), of a flat shape like ticks, which, however, he 

 has not examined particularly. 



In connexion with this I refer to the observations by Creplin (Wiegm. 

 Arch. 1844, i, p. 118, note) on a mite like a Sarcoptes found in large nests, 

 on the extensor, about the rnetatarsal joint, in Strix flammea. 



Erasmus Wilson has laid before the Royal Society of London his 



26 



