SPECIES OCCASIONALLY ANNOYING 341 



table feeders and may do much damage to cultivated plants. 

 One species especially, Tetranychus molestissimus, which lives 

 on the undersides of leaves of a species of cockle bur, Xanthium 

 macrocarpum, in Argentina and Uruguay, attacks man during 

 the winter months from December to February. It produces 

 symptoms similar to those of the louse-mite, with intense itching 

 and some fever. The common " red spider," T. telarius, an 

 almost cosmopolitan species, also is reported to attack man oc- 

 casionally. 



The common chicken mite, Dermanyssus gallinae, belonging 

 to the family Parasitidse (Gamasidae), frequently causes much 

 irritation and annoyance to those who come in contact with it. 

 Although it can thrive and multiply only on certain kinds of 

 birds, it sometimes remains on mammals for some time, causing 

 an eczema or rashlike breaking-out on the skin, attended, as in 

 other mite infections, by intense itching. Except in cases of 

 constant reinfection chicken mites are usually troublesome to 

 man for only a few days at most. Since these mites can live 

 for several weeks without feeding on their normal hosts, places 

 formerly frequented by fowls may be infective after the removal 

 of the birds. The mites normally remain on their hosts only long 

 enough to fill up on blood, usually at night, spending the rest of 

 the time in cracks and crevices in and about the coops. Various 

 sprays of sulphur, carbolic solutions and oils are used to destroy 

 them. An allied species, Holothyrus coccinella, living on geese and 

 other birds on Mauritius Island, attacks man, causing burning and 

 swelling of the skin, and frequently proves quite dangerous to 

 children by entering the mouth. 



A very small mite, Tydeus molestus, belonging to the family 

 Eupodidse, attacks man in much the same manner as do the 

 harvest mites. It is common on some estates in Belgium, ap- 

 parently having been imported many years ago with some Peru- 

 vian guano. It appears regularly each summer on grass plots, 

 bushes, etc., in great numbers, disappearing again with the first 

 frost. It causes great annoyance in red-bug fashion, not only to 

 man but to other mammals and birds as well. 



