82 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvni. 



4. Venter behind witli a siibmarginal crescentic plate; tarsi ratlier long Ilericia 



No such creseentic plate 5 



5. Legs very slender, especially the tarsi; himl legs nfteu bent forward ..H'lMhjxtoma 

 Legs much shorter, the tarsi not slenc ler 6 



6. Four pairs of suckers in the plate arranged 2-2-2-2 xileurobius 



i^uckers not in such arrangement llliizogliiphua and Tyroglyphus 



Of the oenii.s lllstuMoma we have ut least two species. The hypo- 

 pial sta^'e of one (//. muscd/'ani) is often attached to liouse flies; the 

 other species, IL aiiwricnimu)^ was taken under bark, which was also 

 infested with a Rliizoijlyphvx. This species has a number of humps 

 on the dorsum of the body, and upon the summit of each is a small 

 hair. \\\ Europe one species lives 

 in mushrooms, and spreads a dis- 

 ease that causes the decav of the 



Fi<;. l.")N. — (.;].vripiiA(.ri 



Fi(,. 159.— Carpoglyphcs passulakim, .male. 



pileus. Nearly all the species occur in decajdng materials, biit Jensen 

 has recorded that one .species {II. her<jhi) lives parasitical ly in the 

 egg-capsule of a horse-leech in Denmark. The eggs hatch into six- 

 legged larva?, which soon molt into the nymph. The latter devours 

 the embryonic leech and then passes into a Ili/jtojni.s. This escapes 

 from the capsule, attaches itself to an insect, and, on reaching suit- 

 able locality, molts into a full-g"rown njanph. The latter cuts through 

 the capsule, enters, and there transforms to the adult mite. Here 

 reproduction takes place, and the life-C3'cle begins anew. 



The genus (xhjciphagH>< does not appear to l)e as common in this, 

 coimtry as in P^urope, possil>ly owing to their minute size. Two 

 species are known to me, both of rather modest appearance. One has 

 long plumose hairs on the body, and was found in seeds. In Europe 

 several species appear to be connnon in houses and buildings. Some 

 species are provided with many broad scale-like hairs. In all the forms 



