222 Annals .Entomological Society of America [Vol. XV, 



A New Classification of the Suborder Prostigmata. 



A. Chelicerse chelate; adapted for biting; palpi without thumb, 



Section Adactylognatha 

 B. Mouth-parts not formed into a beak; palpi neither geniculate or 



raptorial Eupodida 



BB. Mouth-parts formed into a conspicuous beak; palpi either geniculate or 



raptorial Bdellidcg 



AA.Chelicerae either falcate or needle-pointed, adapted for piercing. 

 B. Legs usually adapted for swimming. Acjuatic mites, 



Section Hydracarina 

 C. Mouth-parts not situated on a beak. Fresh water mites, 



Hydrachnida 

 CC. Mouth-parts situated on a more or less distinct beak. Marine 



mites HaJacarida 



BB. Legs not adapted for swimming. Mites not aquatic. 



C. Legs composed of more than three segments; palpi provided with a 

 thumb, except in degenerate forms, in which case they are fused 



with the maxillse Section Dactylognatha 



D. Chelicerse falcate; palpi free, five-segmented and with the last 

 segment always formed into a thumb. 

 E. First and second legs provided with processes bearing 

 large spines; integument with large chitinous shields, 



Caeculida 



EE. First and second legs without processes bearing spines; 



integument without any large chitinous shield. 



F. Cephalothorax with a rod-like structure at the bottom 



of a median dorsal groove; legs stouter and usually 



with swollen tarsi Trombidiida 



FF. Cephalothorax without rod-like structure and median 

 dorsal groove; legs more slender and tarsi never 



swollen Anystida 



DD. Chelicerag not falcate but either styletiform or needle-like; palpi 



frequently reduced in size and number of segments, and 



variously modified. 



E. Cephalothorax with a rod-like structure at the bottom of a 



median dorsal groove; tarsi not attenuated, but on the 



contrary frequently swollen; body well clothed with 



short set^ Erythraeida 



EE. Cephalothorax without rod-like structure and median dorsal 



groove; tarsi tapering from base to apex; body sparesly 



clothed with setae of varying lengths. 



F. Each tarsus provided with either a pectinate distal 



appendage or tenent hairs, or both of these; palpi 



moderate or small; phytophagous in habits. 



G. Adults with four pairs of legs; palpi free; never 



producing galls Tetranychida 



GG. Adults with less than four pair of legs; palpi greatly 



reduced and united ventrally to form a trough 



for the needle-like cheliceras; usually producing 



and inhabiting galls. 



H. Body not vermiform; adults with six legs; each 



tarsus provided with two claws and two 



"feather hairs;" gall makers. 



Phytoptipalpida 



HH. Body vermiform; adults with only four legs; 



each tarsus provided distally only with a 



single claw and "feather hair". Eriophyidce 



FF. Tarsus usually without pectinate appendages and always 



without tenent hairs; palpi usually large; predaceous 



or parasitic in habits Cheyletida 



CC. Legs stumpy and composed of only three segments; body vermiform. 



Parasitic mites Section Brachypoda 



One family Demodec'da 



