78 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVIII. 



Fiiniily TYROGLYPHIL).^]. 



The Tyi'oglyphida' {Sa/x-optkl/s defr't'olcs of Meg-niii) are not a 

 large family of mites, but many of them are of considerable economic 



importance, since several of them 

 affect stored foods and the roots and 

 bulbs of living plants. They have 

 been known to naturalists from the 

 time of Linmeus. In the adult con- 

 dition they are usuall}^ free, but dur- 

 ing one stage of their life, known 

 as the h3'popial, they are attached 

 to various insects and sometimes 

 small mannnals. This hypopial 

 stage, or hypopus, is a migratorial 

 condition; the mite during this pe- 

 riod takes no food, so it is not a 

 true parasite. However, in some 

 cases where they occur in enormous 

 numbers thev may injure the insect, 

 owing to their weight or position. 



The Tyroglyphidffi are pale-col- 

 ored, soft-l)odied mites, devoid of 

 trachetv, usually with prominent 

 chelate mandiljles, small palpi, mod- 

 erately long legs, ending in one claw 

 and often a sucker. The body is about twice as long as broad, and 

 liroadest behind the middle. There is commonly a distinction between 

 the cephalothorax and abdomen. 

 There are no eyes (unless certain 

 organs in a few Hypopi are eyes). 

 The dorsum bears a few, mostly 

 long hairs, and the legs have scat- 

 tered hairs. One hair near the end 

 of the penultimate joint of legs land 

 II is very long, and there is usually 

 a clavate hair near the base of the 

 tarsi of legs I and II. It may be a 

 sense organ. It is always in this 

 position although authors sometimes 

 figure it as arising from the preced- 

 ing joint. On the venter are the 

 usual apertures. The genital is usu- 

 ally elongate, and situate between 



the hind coxaj; there are often two U-shaped marks each side of it, 

 known as the genital suckers. The anal opening is usually nnich 



•TYKOGLYPHCS SP. (PERGANDEj. 



Fig. 154.— Hypopus of a tykoglyphus, from 



BELOW. 



