THE ACAEINA OR MITES. 



27 



But little is known of their habits. The free-living forms move slowly and are so 

 small that they have not often been watched by naturalists. Most of them are pale- 

 colored, unmarked, but a few have dai-ker 

 marks; some are clothed with ribbed, 

 scalelike hairs. The eggs are deposited 

 singly or in clusters, and by some species 

 a web is spun over them, or at least a few 

 threads to hold them in place. In a few 

 species the mother remains to guard the 

 cluster for some time. The larva, upon 

 hatching, has much resemblance to the 

 adult, but, of course, only six legs. The 

 nymph looks still more like the pai'ent, 

 and there ai-e but few differences between 

 the sexes save that the male is smaller. 

 Cheyletidse feed on animal life, some be- 

 ing predaceous, others pai-asitic. A few 

 may be said to belong to both groups, in- 

 asmuch as they occiu- upon certain ani- 

 mals only to prey upon the parasites of 

 the host. 

 Only a few genera are known, and of 



{ these but six have been recorded from 



! this country. 



2Q.— Cheylctus audax, from below, 

 illustration.) 



(Author's 



2 

 5 

 3 



1. Leg I fitted to clasp hair, with 



one large cui'vedclaw; hind -^^S- 



legs with one claw Myohia. 



Leg I not fitted to clasp hair; hind or front legs with two claws 



2. Palpi cur\T.ng toward each other to form a forceps 



Palpi not forming a forceps 



3. Body elongate; palpi simple; a plumose or forked pulvillus to tarsi Picohia. 



Body short and broad 4 



4. Hind legs with claws; palpi without recurrent hooks Psorergates. 



Hind legs without claws, very short and tipped with bristles; palpi with 



recurrent hooks Harpyrynchus. 



5. Tarsus (or papilla) of palpus with only simple hairs, no combs; body short 



and broad Cheyletiella. 



Tarsus (or papilla) with pectinate bristles 6 



6. Palpus with a comb 7 



Palpus without a comb; only the anterior dorsal shield present, which is 



acute behind; body elongate Cheletoides . 



7. Palpus with but one comb 8 



Palpus with two combs 9 



8. With two large dorsal shields, not far apart; body not very long Acaropsis. 



With but one (the anterior) shield; or a small one near tip of body; body 



elongate Cheletopsis. 



9. With broad, scalelike or fan-shaped hairs; an eye spot each side Cheletia. 



Without such broad scalelike hairs; usually no eye spots Cheyletus. 



Cheyletus (fig. 24) contains many species; a number have been found on the skins 

 of birds, where they doubtless feed on the parasitic analgesid mites. They are very 

 small (about 0.5 mm. in length), live freely, and prey upon other mites and small 

 insects. They seize the prey with their big palpi, insert the mandibles, and suck it 

 dr>'. Some have thought that there must be poison glands in the palpi, since the prey 

 ceases movement very soon after capture. Two species, one of them C. clavispinus 

 Banks, have been found attached, in adult condition, to Hemiptera of the genus 

 Aradus. They are evidently not parasitic, but use the insect only for transportation. 

 Another of our species, C. pyriformis Banks (fig. 25) was found feeding on a scale insect 

 on grapevine, another on Cicada eggs, and a third, C. audax Banks (fig. 2G) attacking 



