134 REPORT 108^ U. S. DEPAETMEXT OF AGRICULTURE. 



Superfamily DEMODICOIDEA. 



Family ERIOPHYID^. 



The members of this family, long known as Phytoptidae ^ are among the most curious 

 forms of the Acarina. They are extremely minute, but make up by their great num- 

 bers. They are strictly plant feeders, and many of them cause galls, fuzzy spots, or 

 other deformations on plants. These ^alls, unlike many insect galls, have an opening 

 through which the mites may pass. The adult mite (fig. 277) has but four legs, all 

 near the anterior part of the body, the posterior pairs being wholly lacking or repre- 

 sented by fine hairs. The body is divided into two parts — the anterior, short and 

 broad, is the cephalothorax; the posterior, long, tapering, and multianmilate, is the 

 abdomen. There are a pair of free three-jointed palpi, and between them the rostrum, 

 from which may project the needlelike mandibles. Near the base of the abdomen, 

 beneath, is the genital opening, the female epigynum being quite large and prominent; 

 the male epiandrum is much smaller. At the apex of the abdomen is a truncate piece, 



Fig. 277. — Eriophycs sp., side view. (Author's illustration.) 



the telson, from which arise two long hairs, the caudal setae, and sometimes other 

 shorter ones. There are also a few other hairs on the body arranged in pairs (usually 

 five) and useful in distinguishing species. At the tip of the abdomen is a sucker formed 

 of two semich'cular flaps which can be extended or retracted at the will of the animal. 

 The legs are five-jointed, short, and end in a single tarsal claw, beneath which is a 

 plumose hair, known as the "feather hair." The cephalothorax often shows A-arious 

 lines or ridges. The number of rings or annulatious on the abdomen varies^ccording 



to the species, and in some forms there are more divi- 

 sions above than below. In size few of the Eriophyida> 

 reach one one-hundredth of an inch, and many are not 

 half so long. 



Tlie Eriophyidss have had a checkered liistory. Tlie 

 early botanists, unable to see the miniite creatures, 

 _ _^ supposed that the galls and fuzzy spots were fungi and 



•^r-^W— -^-1 ~^— IIZrl,i_ so described them, the genus Cephaloneon being founded 

 ^— C_CllZC_IIXZI_IE_ on distinct galls, Volvolifex on rolled edges of leaves, and 

 Fig. 278.— Egg of an Eriophycs in Erineum and Phijllerium on the fuzzy patches, 

 gall. (Author's illustration.) In 1832 Duges, who was the first to look carefully 



into these galls, supposed that the mites were imma- 

 ture since they had but two pairs of legs. He saw the eggs (fig. 278), but sup- 

 posed that the adult mite had come into the gall to lay the eggs and then went 

 out to deposit eggs elsewhere. In 1851 Dujardin examined some galls, found 

 the mites, and noticed Avitliin some of them objects which he took to be eggs. 



1 The change of name of this well-known group of mites seems inevitable, although much 

 (o be deplored. PJriophi/Cfi Siebold hn.s <i year's priority over Phi/toptus Dujardin. But 

 {■Uel)old did not carefully sludy th(>se mites at all and supposed tlieni to be immature crea- 

 tures. Dujardin recognized their true nature and made many careful observations upon 

 them. European authors, however, have recently adopted Eriophyes. 



