314 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



marks that the "Eumcnes establish for their offspring sepa- 

 rate and distinct cells formed of earth. The Zethus build 

 their nests composed of aggregated cellules, established com- 

 monly in vegetable matters, and fixed upon little branches 

 of trees. The Odynerus nidificate in holes in walls, in the 

 stems of plants, etc. The Montezumia, finally, construct 

 their houses of many rooms, a little like those of Zethus, but 

 very much more massively built of earth and stuck 

 against walls or rocks, as are those of the Spheyides and 

 some of the mason bees." 



The Demodex folllculorum is a worm-shaped minute mite, 

 which lives in the sebaceous and hair-follicles of the skin in 

 man and some mammals. M. Megnin has lately published 

 a full account of it. It is said to be viviparous, the fe- 

 male producing small footless contractile larva?, without any 

 mouth organs, which shortly after their birth acquire three 

 pairs of short wart-like feet. After a change of skin a fourth 

 pair of legs appear, as well as traces of a beak. After a sec- 

 ond change the perfect Demodex is produced, but still with- 

 out the sexual organs, which appear later. Megnin distin- 

 guishes three if not four forms of these parasites, which, 

 however, he prefers to regard for the present as varieties of 

 a single species Demodex folllculorum. The commonest 

 of these appears to be that of the dog (var. caninus), which 

 inhabits the hair-follicles of all parts of the body of that ani- 

 mal; a smaller variety (D. catl) is found almost solely in the 

 sebaceous glands of the ear of the cat; and a larger one (var. 

 Jiominis) in the follicles of the human face. M. Simon also 

 met with similar parasites in the glands of the margin of the 

 eyelids in sheep (var. ovis) ; but no other writer has ever 

 seen them there. In the dog the presence of these parasites, 

 which occur in great numbers together in the hair-follicles, 

 produces a regular skin-disease or mange; but this does not 

 appear to be transmissible to the human subject. 



M. Megnin has studied certain mites {Kytodltes ylaber 

 Megnin) which live in the air- sacs and cellular tissue of 

 birds. They are of two kinds, one of perfect form (Sarcop- 

 tes cisticola), the others vermiform, which are the pupa? of an 

 external mite [Pterollchus fedciyerus Megnin). The subcu- 

 taneous life of this form tends to preserve the species from 

 complete annihilation resulting from the casting of the feath- 



