218 



Annals Entomological Society of America [Vol. XV, 



THE TARSAL ARMATURE IN THE ERIOPHYID.-E AND IN 

 PHYTOPTIPALPUS. 



The Tarsonemid theory of the origin of the Eriophyidas 

 fails utteriy to explain the presence of the peculiar tarsal 

 armature of the gall mites. In the Eriophyidas each tarsus 

 is armed at its tip with a simple claw and below it with the 

 pectinate structure known as the "feather hair" (Fig. 3, c). 

 The so-called "feather hair" is composed of an almost straight 

 central part from which branch off below four or five pairs of 

 barbs. 



Of all the groups of the Acarina no other group gives as 

 close an approximation to the Eriophyid type of tarsal armature 

 as the red spiders, or spider mites. Of the various genera of 



Fig. 3. Tarsal armatures oi Syncaligus, a; oi Phytoptipalpiis,h; 

 and of Eriophyes, c. 



the spider mites the genus Syncaligus, a genus showing many 

 relationships with Phytopti palpus, has a tarsal armature most 

 nearly like that of the Eriophyidae. In this genus there is 

 a ventral structure, the empodium (Fig. 3, a), which differs 

 from the "feather hair" of the Eriophyidas only in being stouter 

 and having one or two less barbs, or branches. In addition to 

 the empodium in Syncaligus, two tarsal claws are present. 

 It is from the Syncaligus type of tarsus that the tarsal armature 

 of both Phytoptipalpiis and the Eriophyidae have probably 

 been developed; in Phytoptipalpus by the splitting of the 

 empodium into two and an increasing of the number of its 

 branches, and in the Eriophyidae by the atrophy of one of the 

 tarsal claws. That one of the tarsal claws is easily lost is shown 

 repeatedly in the Acarina. Even in the Tetranychidas it is now 



