October, '17] ewing: economic mites 497 



NEW SPECIES OF ECONOMIC MITES 



H. E. Ewing, Iowa State College, Ames, la. 



In the following paper seven species of mites are described. Six of 

 these species are injurious, some being quite serious pests, and one 

 species is beneficial, being predaceous. Of the seven species described, 

 six are new, and the remaining species, Tarsonemus pallidus Banks (?), 

 may prove to be new in the future. This species, which is the one that 

 seriously injures cyclamens, does not agree with Mr. Bank's descrip- 

 tion of pallidus, but probably is the species described by Banks, as 

 specimens agree fairly well with material determined by Banks as T. 

 pallidus. 



Tetranychus uniunguis n. sp. 



A greenish yellow species. Palpi rather stout, reaching the tip of tibia of leg I. 

 Palpal claw rather short, strongly curved and not very sharp at its tip. Thumb of pal- 

 pus stout, as broad as long, reaching, but not surpassing, the palpal claw; finger of 

 thumb situated in the middle of the apex, about twice as long as broad, and rounded 

 at its tip. Hairs of thumb distributed as follows; two small ones on the inside of 

 thimib near its apex, one long hair, about as long as the thumb itself, on the inside 

 near the base, and another of about equal length on top not far from the base. Cheli- 

 cerae each arising near the base of plate, and making an evenly rounded loop posteri- 

 orly, and then passing forward for about two-thirds their length, then in a downward 

 direction to their tips. The only place that the cheUcerae are swollen is near their 

 bases. Tarsus of leg I considerably longer than the tibia. Tarsi each ending in a 

 single claw, which is not strongly curved, but is very sharp; two tenent hairs. Length, 

 0.59 mm. ; width, 0.42 mm. 



From Urbana, Illinois; on arbor vitae {Thuja occidentalis) ; by the 

 writer. 



Tetranychus multidigituli n. sp. 



Preserved specimens yellowish. Body somewhat depressed, skin more or less 

 wrinkled, and abdomen somewhat pointed behind. Palpi prominent; claw, strong 

 and much ciu-ved; thumb stout, almost as broad as long, and not surpassing the claw; 

 digit or finger about half as long as thumb and less than half as long as broad; digituU, 

 or spines, at least five near the tip of thumb, setae also present on thumb. Mandibles, 

 or chelicerse, slender, with a simple loop toward base, and of uniform diameter except 

 at base where they are slightly swollen. A single pair of eyes present, placed laterally; 

 cornea strongly curved. Abdomen clothed above with rather stout, simple, sUghtly 

 cm"ved setae. Legs moderate ; tarsus of leg I about one and a third times as long as 

 tibia, and truncate at its tip, from which springs a very long tactile seta. Tarsal 

 claws rather weak, strongly curved near their bases, beyond which they are divided 

 into six prongs. Onychium with four tenent hairs. Length, 0.30 mm.; width, 0.21 

 mm. 



From Wooster, Ohio; on bark of honey locust, Gleditsia triacanthos; 

 by J. S. Houser. Several specimens. This species differs from most 

 of the other species in the genus in having several digituli, or setae, to 



