[The chief genera are Tyroglyphus, Rhizoglyphus, Glyciphagus, Aleurobius and Histiogaster. The first three have typical characters referred to, but are distinguished from each other by the two former having the hairs on the dorsum smooth, whilst in Glyciphagus they are hairy, plumose, or feathered. Rhizoglyphus can be told from Tyroglyphus by having claws on the tarsi without any suckers; Tyroglyphus has both claws and suckers. The larvæ are hexapod and may become adult in the usual way by repeated moults, or they enter the so-called hypopial stage. In this the eight-legged nymph becomes quiescent, and during this stage it fixes itself to some insect or other animal by a patch of suckers on the lower surface of the hind end of the body, and is so carried from place to place. The hypopus does not feed and has a hard shell and short legs. When it has reached a new home it moults and development proceeds in the normal way. Canestrini and Kramer treat the Tyroglyphidæ as a sub-family of the Sarcoptidæ, calling them sub-family Tyroglyphinæ, the other sub-families being Sarcoptinæ, Canestriniinæ and Analsinæ.—F. V. T.]
Sub-family. Tyroglyphinæ.
Genus. Aleurobius, Canestrini.
Aleurobius (Tyroglyphus) farinæ, de Geer (part), Koch.
The male measures 0·33 mm. in length by 0·16 mm. in breadth; the female 0·6 mm. in length by 0·3 mm. in breadth. These mites possess five pairs of suctorial organs of a light colour; the legs are reddish. Moniez observed them in Lille on the skin of labourers who had been unloading Russian corn. A few of the species generally mentioned under the designation of Tyroglyphus siro are probably the common flour-mite, which also occurs on dry cheese.
[The farinæ of de Geer is an Aleurobius described by him in 1778 (“Mém. Hist. Ins.,” vii, t. 5, f. 15, p. 97) as Acarus farinæ.—F. V. T.]
Genus. Tyroglyphus, Latreille.
Tyroglyphus siro, L., 1756.
(Defined by Gervais, 1844.)
Male 0·5 mm. in length by 0·25 mm. in breadth; female 0·53 mm. in length by 0·28 mm. in breadth; the males have two suckers on the tarsi of the fourth pair of legs. Penis straight, colour whitish or reddish.