682 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



barely equals trochanter I. Tip of tarsus bears a stout, sickle-shaped 

 claw, which is uncleft to its tip; arising from the under face of this 

 claw, near its base, are six weak spines, which are less than one- 

 fourth the length of the main claw. The usual series of four capitate 

 hairs arise by the sides of the base of the claw from the tip of the 

 short onychiimi. The egg is unknown to the writer. 



Type.— Cat. No. 20164, U.S.N.M. 



The type material was collected by Mr. E. W. Rust "along the line 

 of the Ferrocarril Central del Peru near La Legua (between Lima 

 and Callao), Peru, South America, January, 1913, from the under- 

 side of willow {Salix, species) leaves." The species is somewhat 

 intermediate between T. hicolor Banks and T. y other si McGregor, 

 but is in no wise closely allied to either species. 



Notes. — An ample series of measurements of mounted materia 

 in fair condition have yielded the following averages for adults of 

 both sexes. 



The relative lengths of the leg joints are as foUows: Coxa 9, tro- 

 chanter 10, femur 16, patella 9.5, tibia 9.5, tarsus 10. 



Mr. Rust states that the presence of tliis species causes the willow 

 leaves to turn yellow and drop, but did not appear to greatly injure 

 the trees. He says that the individuals live in restricted colonies 

 under small, compact webs which almost completely conceal them. 

 These webs, according to Mr. Rust, resemble very much the webs 

 under which many time spiders deposit their eggs. No predaceous 

 species were observed in the mite colonies. 



TETRANYCHUS RUSTI, new species. 



Color ranging from yellowish or greenish to red. Eyes (in mounted 

 material) translucent, directly over coxae II and between subfrontal 

 and posterior cephalo thoracic bristles. The dorsal epidermal append- 

 ages are not distributed to conform with the usual arrangement for 

 this genus, but a series of 26 shortish, nontapering, sparsely serrate, 

 rod-like appendages are distributed on the dorsal aspect of the body 

 as follows: One at either side of mandibular plate anteriorly, one 

 just anterior to each eye, one just posterior to each eye, six forming a 

 fringe at hind margin of body, three along each side of abdomen, a 

 series of four along the anterior margin of abdomen, one on either 

 side of median axis in Une with coxae III, and one on either side of 



