NO. 13.^2. THE ACARINA OR MITES— BANKS. 19 



The eg'g's are deposited singl}' or in clusters, and by some species a 

 web is spun over them, or at least a few threads to hold tliem in place. 

 Ill a few species the mother remains to guard the cluster for some 

 time. The larva, upon hatching, has nuich resemblance to the adult, 

 but, of course, with only six legs. The nymph looks still more like 

 the parent, and there are but few differences between the sexes, save 

 that the male is smaller. Several authors have noted the existence of 

 parthenogenesis in some species. Cheyletida3 feed on animal life, 

 some being predaceous, others parasitic. A few may be said to belong 

 to l)oth groups, inasmuch as they occur upon certain animals only to 

 pre}' on the parasites of the host. 



Only a few genera are known, and of these ])ut four have been 

 recorded from this country. 



1. Anterior leg fitted to flanp hair; hind legs with hut one claw; palpi small. . . Mijohia 

 Anterior legs not so modified; hind legs with two claws, or else leg I with two 



claws 2 



2. Body elongate, at least tliree times as long as Ijroad, pal|)i not swollen at 1)ase, no 



distinct "thumh ' or papilla 8 



Body not twice as long as broad, the paj^illa usually jiresent 4 



3. Anterior legs much larger than posterior pairs, and ending in a long ])ifid jml- 



villus Picoliia 



Anterior legs barely longer than others, without such pulvillus Si/rimjiij)Jiilus 



4. Body about as broad as long; legs very sliort and stout; ]ialpi not swollen on 



outer side at base; parasitic forms 5 



Body plainly longer than broad; legs more slender; jialpi usually swollen on outer 

 side at base; hind legs with claws; not true jmrasites (3 



5. Hind legs each with two claws Psorergates 



Hind legs without claws; with several long hairs Harpi/rhi/ncJiufi 



6. Tul»ercle, or papilla, of palpus with one or two pectinate bristles ClicyJetus 



Tubercle, or papilla, of palpus Avith only simple hairs Cliei/k'tidld 



Cheyletus contains about one dozen species. The}^ are very small 

 (about one-half millimeter in length), live freel}', and prey upon other 

 mites and small insects. They seize the pre}' with their big palpi, 

 insert the mandibles, and suck it (Sxy. Some have thought that there 

 nmst l)e poison glands in the palpi, since the prey ceases movement 

 ver}- soon after capture. Several species have some fan- shaped hairs 

 or scales on the body and appendages. These constitute the subgenus 

 Cltcyhiln Haller. Two species, one of them, C. clarisp(ijiu>i Banks, 

 have been found attached, in adult condition, to Hemiptei-a of the 

 genus Aradus. They are evidently not parasitic, but use the insect 

 only for transportation. Another of our species, C. j>i/rtforin!s., was 

 found feeding on a scale insect on grapevine, another on Cicada eggs, 

 and a third, C. aadax, attacking T3'rogl3'phids among cabbage seed. 



Cheyh'tlella includes several species in which the palpi are not as 

 large as in CJieyletus. They usually occur on birds where they feed 

 on the other mites present. They have l>een called auxiliary parasites. 

 One species, C. parasitivorax^ uses the rabbit's fur as a hunting forest, 



