NORTH AMERICAN TETRASTICHUS — BURKS 543 



obsolescent or wanting, paraspiracular carinae absent, a few vague 

 wrinkles present at posterior margin ; spiracles large, contiguous with 

 anterior margin, mesal length of propodeum one-third length of meso- 

 scutellum ; gaster and thorax equal in length. 



Male. — Length, 0.7-0.9 mm. Antennal scape broadened from base 

 to apex, twice as long as pedicel, each funicle segment bearing long 

 setae on a basal elevation, first segment shorter than others, all funicle 

 segments and club equal in width ; fringe at posterior margin of hind- 

 wing one-half as wide as wing at hamuli; gaster equal in length to 

 thorax ; male genitalia prominent, apparently never wholly retracted 

 into abdomen, sagittae elongate, acutely pointed, aedeagus long, nar- 

 row, acute at apex. 



Type locality. — Five miles northwest of Marinette, Ariz. 



Types.— V. S. N. M. No. 56243. 



Described from many male and female specimens, as follows : Fe- 

 male holotype, male allotype, and 5 female and 6 male paratypes, 

 reared from nymphs of Paratrioza cockerelli (Sulc), April 9, 1935, 

 by V. E. Komney; 17 female and 13 male paratypes, from 10 miles 

 north of Phoenix, Ariz., reared from nymphs of Paratrioza cockerelli, 

 April 1935, V. E. Romney; 3 females, Mesilla Valley, N. M., reared 

 from Paratrioza cockerelli (?), October 1923, Chittenden No. 6900; 

 1 male, Hollister, Idaho, June 2, 1931, D. E. Fox; 1 male, Hobbs* 

 Butte, Idaho, June 11, 1931, in wind-vane trap ; 2 females, Lawrence, 

 Kans., reared from (?) Calophya nigripennis Riley, 1930, P. B. Law- 

 son; 3 females, Spanaway, Wash., reared from infested Amelanchier- 

 berry material, August 26, 1933, W. Baker; 5 females and 4 males, 

 Billings, Mont., September 2-3, 1939, from Paratrioza cockerelli on 

 tomato, H. B. Mills; 23 females and 29 males, Billings, Mont., Sep- 

 tember 11, 1939, from Paratrioza cockerelli nymphs, D. J. Pletsch; 9 

 females and 6 males, Colorado, February 12, 1940, from Paratrioza 

 cockerelli on potato, Hill and Tate; 1 female and 5 males, Garden 

 Grove, Calif., September 17, 1928, A. C. Davis ; and 12 females and 2 

 males, Fort Collins, Colo., December 13, 1932, Colo. Agr. Coll. No. 

 5319. Many additional males and females, not included in the type 

 series, were reared at Billings and Bozeman, Mont., from nymphs of 

 Paratrioza cockerelli during September 1939 by D. J. Pletsch. Other 

 specimens, not included in the type series, are from Scottsbluff, Nebr., 

 reared from Paratrioza cockerelli on potato, August 20, 1939, by John 

 Standish. 



Remarks. — This species and T. dyrus evidently are closely related to 

 Tetrastichus dryi Waterston, which parasitizes "Trioza citri" in Kenya 

 Colony, Africa, and Tetrastichus radiatus Waterston, parasitic on 

 Euphalerus citri (Kuwayama) in the Punjab, British India. All four 

 species apparently possess the same general kind of remarkable male 

 genitalia. 



