A NEW WHEAT THRIPS 



By E. O. G. Kelly, 



Entomological Assistant, Cereal- and Forage-Insect Investigations, 



Bureau of Entomology 



INTRODUCTION 



A new wheat thrips, Prosopothrips cognatus Hood, was described by 

 Mr, J. D. Hood,* of the Biological Survey, from material collected by the 

 writer in 1908. As it is a new species without synonyms, there are, 

 up to this time, no records of its having been destructive. The data 

 contained in this paper have been collected during the last few years 

 whenever the insect occurred in numbers sufficient for study. This 

 species frequently becomes injurious to wheat {Triticum spp.) in localized 

 areas, but has not yet been found doing injury to oats {Avena saliva) or 

 other grain crops. 



DISTRIBUTION OF THE SPECIES 



This wheat thrips occurs in all parts of Kansas, even to the western 

 border; in Oklahoma; at two places in western Missouri; and in one 

 locality in extreme southern Nebraska. Careful search has been made 

 for it in northern Texas, eastern New Mexico, and western Nebraska, and 

 in Kentucky, Tennessee, and Georgia, with negative results. 



DESCRIPTION AND LIFE HISTORY 

 THE EGG (PL. XXX, FIG. l) 



The female deposits her eggs in the tissue of the young leaves, usually 

 on the ventral side, whether in wheat or grass, by first cutting the tissue 

 with her sharp mandibles, then thrusting the short ovipositor into the 

 lacerated leaf and placing a single, tiny e.gg in each puncture. 



The egg when first deposited is translucent and nearly colorless, taking 

 on a greenish tinge just before hatching. It is somewhat kidney-shaped, 

 about 0.35 mm. in length, and 0.125 mm. at its greatest diameter. 



The hatching period varies from 6 to 10 days and is about the same 

 in the laboratory as under natural conditions in the field. 



THE LARVA (PL. XXX, FIG. 2) 



The greenish tinge observed a few hours previous to the issuing of the 

 tiny, slender larva remains with the larva until after it begins to feed, 

 when the color changes to a deeper green as the juices of the plant are 

 imbibed. 



iHood, J. D. Prosopothrips cognatus, a new North Axnerican Thysanopteron. In Canad. Ent., v. 46, 

 no. 2, p. 57-59, fig. 13- 1914- 



Journal of Agricultural Research, Vol. IV, No. 3 



Dept. of Agriculture, Washington, D. C. June 15, 1915 



K-17 

 (219) 



