Trombidiformes 147 



superfamilies, but since this grouping is still in the formative stage no 

 attempt is here made to present categories other than families. 



Key to the Trombidiformes 



1. Body of normal shape, not wormlike (except in Demodicidae); 

 with normal four pairs of legs (except certain cases in Podapo- 

 lipodidae and Phytoptipalpidae) ; with or without well-developed 

 gnathosoma; with respiratory system 2 



Body wormlike, annulate; with only two pairs of anteriorly placed 

 legs; no respiratory system; gnathosoma greatly reduced; palpi 

 minute, lying close to rostrum; chelicerae stylet-like; minute plant- 

 feeding mites Tetrapodili (Eriophyidae) 



2. Chelicerae tiny, stylet-like; palpi minute, lying close to rostrum; 

 gnathosoma as a whole greatly reduced, inconspicuous; tiny mites 

 with or without usual number of legs; stigma of 2 behind max- 

 illae; i without stigma or tracheae Tarsonemini 



Chelicerae much larger, easily seen; palpi not minute nor lying 

 close to rostrum (except the wormlike Demodicidae which has 

 four pairs of legs); gnathosoma usually conspicuous; as a whole, 

 large mites with four pairs of legs (except in Phytoptipalpidae 

 where one genus possesses only three pairs of legs); stigma open- 

 ing at base of chelicerae {Demodex without stigma or tracheae) 



Prostigmata 



TETRAPODILI BREMI, 1872 



These are minute, w^ormlike, plant-feeding mites measuring up to 

 0.20 mm. in length. They possess two pairs of legs anteriorly which 

 lack tarsal claws but which have a "featherclaw." The body is ringed 

 and the genital opening is located just behind the legs and is covered 

 by a transverse plate. There are no eyes, no heart, no excretory sys- 

 tem, and no respiratory system. Only a few setae are present. The 

 Tetrapodili contains only a single family, the Eriophyidae. 



Eriophyidae Nalepa, 1898 



Figure 106 



Diagnosis: The eriophyids are minute, wormlike mites whose propo- 

 dosoma is shieldlike and has distinctive, specific patterns. The hys- 

 terosoma is elongated and annulate. These mites do not possess a 

 respiratory system. Two pairs of anterior legs are present in all stages 



