THE ACAEINA OR MITES. 



109 



waitei Banks attacks the grovring terminal twigs of peach trees and turns them into 

 elongate, blackened, and distorted galls with many small lateral twigs and leaves 

 growing from them. But few remedies have been proposed for these mites. A mix- 

 ture of powdered sulphur in soap and water has been suggested for one on sugar cane. 

 Picking infested parts has also been recommended. 



The genus Tarsolarhus Thor is very similar to Tarsonemus, but has a pulvillus 

 between the tarsal claws, and the body is slender and clothed with bristles; it occurs 

 in moss in northern Europe. The curious genus Scutacarus (fig. 225) has a migratorial 

 nymphal stage much like the hypopus of the Tyroglyphidae. This stage has been 

 found on bees and ants. The adult occurs on plants and among dead leaves. Amer- 

 ican species have been taken from bees of the genus Apis, Halictus, and Nomia 

 Berlese describes several species from ants. 

 He has divided the genus into three genera, 

 as follows: 



1. Leg I without claw Diversipes. 



Leg I with a claw 2 



2. Leg IV without terminal caroncle. 



Scutacarus. 



Leg IV with terminal caroncle.. 



Imparipes. 



Most of the few known species remain in 

 Scutacarus. This genus was first described 

 by Gros in 1845, and renamed Disparipes by 

 Michael, who did not know of Gros's paper. 



The species of Imparipes (fig. 226) have Jf 4,. / ^ 



little resemblance to ordinary mites. 



Family TYROGLYPHID^. 



The T>Toglyphid8e ("Sarcoptides detri- /^a//"Vp /:.->?■/ 



coles" of Megnin) is not a large family of 

 mites, but many of them are of considerable 

 economic importance, since several affect 

 stored foods and the roots and bulbs of living 



plants. They have been known to natural- / / 11 \\ 



ists from the time of Linnaeus. In the adult / | j \ \ 



condition they are usually free, but during 

 one stage of their life, known as the hypopial. Fig. 227.— Tyroglyphus sp. (From Marlatt.) 

 they are attached to various insects and 



sometimes small mammals. This hypopial stage, or hypopus, is a migratorial condi- 

 tion; the mite during this period takes no food, so it is not a true parasite. However, 

 in some cases where they occur in enormous numbers they may injure the insect, 

 owing to their weight or position. 



The Tyroglyphidae (fig. 227) are pale-colored, soft-bodied mites, devoid of tracheae, 

 usually with prominent chelate mandibles, small palpi, and moderately long legs end- 

 ing in one claw and often a sucker. The body is about twice as long as broad, and broad- 

 est behind the middle. There is commonly a distinction between the cephalothorax 

 and abdomen. There are no eyes (unless certain organs in a few hypopi and in Car- 

 poglyphus are eyes). The dorsum bears a few, mostly long, hairs, and the legs have 

 scattered hairs. One hair near the end of the penultimate joint of legs I and II is 

 very long, and there is usually a clavate hair near the base of the tarsi of legs I and II, 

 which may be a sense organ. It is always in this position, although authors sometimes 

 figure it as arising from the preceding joint. On the venter are two apertures; the 

 genital is usually elongate, and situate between the hind coxae, and there are often two 

 U-shaped marks each side of it, known as the genital suckers. The anal opening is 



