Injurious to Man. 1 3 



found in birds' nests. Many other species of ticks have been 

 recorded as attacking man, including species like Dermaeentor 

 venustus and Ixodes ricinus, which are found on many hosts, and 

 others like Argas persicus (the fowl-tick) and A. reflexus (the 

 pigeon-tick), which are more restricted in habit. Some of the 

 little blood-sucking mites of the family Gamasidae also sometimes 

 leave their proper hosts and bite human beings, viz., Dcrmanyssus 

 gallinae (parasitic on the domestic fowl, cage-birds, etc.), Lipo- 

 nyssus bursa (parasitic on the domestic fowl), L. bacoti (parasitic 

 on the brown rat), and a few. others. 



2. Species parasitic during only part of their life (the 

 " harvest bugs "). — It is only during the larval stage that the 

 species of Microtrombidium and other similar forms suck blood. 

 The adult mites are predatory, feeding on minute insects, etc. 



3. Predatory species which occasionally become parasitic— 

 Pediculoides ventricosus can be placed here. Although normally 

 feeding on the larvae of various insects, this species can transfer 

 itself to man, causing serious trouble. The species might more 

 properly be considered to be a parasite rather than a predaceous 

 form, for it is very minute as compared with the bulk of the larva 

 it feeds upon, and the latter only succumbs if attacked by a 

 number of the mites. 



4. Species, normally feeding on detritus, which may become 

 parasitic. — The species belonging to the family Tyroglyphidae 

 feed on decaying vegetable or animal matter, but a number of 

 them are occasionally parasitic. 



5. Poisonous species. — Holothyrus coccinella, a mite which 

 secretes an irritant poisonous fluid. 



The more important human parasites are given below in their 

 proper systematic order. 



Sub-Order— VERMIFORMIA. 



Fa jiily— DEMODIGII) A E. 



Genus — Demodex, Owen. 



Demodex fol licit torn in, G. Simon. 



In general appearance the mites of the genus Demodex are 

 lather like gall-mites (Eriophyidae), but have four pairs of very 

 short legs, instead of only two pairs as in that family. They are 



