OP THE STATE ENTOMOLOGIST. 53^ 



A singular feature in the life-history of many of the species of the 

 genus Tyroglyphns is the fact that under certain conditions an en- 

 tirely different form, with a hard brown chitinous covering or shield^ 

 and characterized by Duges as a new genus by the name of H'ypopus^ 

 develops within the softer body and finally issues from it by splitting 

 open the softer skin. Claparede,* who believed this form to be the 

 male, has carefully described and figured (he process of change in the 

 European Hypo2)us Dujardinii^ and that Tyroglyj^hus phylloxerce has 

 its Ilypoptis form was independently proved by Prof. Flanchon and 

 myself — the letters announcing the observations on either side having 

 crossed en route. 



Hypopus^ as already stated, has been found preying upon living 

 animals. Tyroglyphus is a slow traveler, and with its soft body can 

 not endure exposure to the air, or resist the attacks of other minute 

 animals. Yet it is ubiquitous, living both above and below ground 

 and swarming on decomposing animal and vegetal substances. When 

 these have once been consumed or reduced to dry powder, what 

 becomes of the swarming mites? M. Maguin has, I think, rightly 

 answered the question. All adult and old mites, together with the 

 young hexapod larvae, perish; but those in the adolescent stage, the 

 octopod pupae, are preserved by their power of putting on a coat of 

 mail which protects them against external influences until they can 

 attach themselves to some living and moving animal, (Hies, beetles, 

 spiders, millipeds and larger animals), which become their carriers 

 and transport them to places which they could otherwise never reach, 

 and where, finding appropriate food, they throw off the disguise and 

 breed as Tyroglyphs, with their well-known fecundity. 



Associated with this predaceous mite, I have found another 



{Hoplophora arctata Riley, Fig. 17), of very curious form, reminding 



[Fig. 17.] one strongly of a mussel •; 



and I refer to it in this con- 



^y' nection because I once 



i strongly suspected it like- 



] Jj wise to be, in some way, re- 



/ V lated to the soft-bodied Tv- 



roglyphs. In studying these 



HOPLOPHORA arctata: a, &, c, rf, p, (liflerciit attitudes a.ssunied .. i xi • i i -i. t 



by it;/, strongly magnified leg. mitOS and their hablts, 1 



had frequently filled vessels with grape roots from which all but Tyro- 

 glyphs and Phylloxera^liad, to all appearance, been carefully excluded ; 

 only to find, on subsequent examination, a number of these mussel-like 

 Hoplophoras and a corresponding decrease in the number of Tyro- 



"Siudien an Acariden, Leipzig, ISCS. 



