30 MISC. PUBLICATION 17 4, U.S. DEPT. OF AGRICULTURE 



IMPORTANCE 



Although Ditropinotus aureoviridis is said by Phillips to be one of 

 the most important parasites of the wheat jointworm, it cannot be 

 ranked as of much importance as a parasite of the hessian fly. Hill 

 and Smith record an average annual parasitization by it of approxi- 

 mately 1 percent of the spring generation of the fly in Virginia, 

 Maryland, and Pennsylvania. In only 2 out of the 10 years covered, 

 by their investigations did it appear at all as a parasite of the fly in 

 the region covered. 



PSEUDERIMERUS MAYETIOLAE Gahan 



(Fig. 7) 



Pseuderimerus mayetiolae Gahan, U.S. Natl. Mus. Proc. 55: 125, fig. 2, 1920; 

 Packard, U.S. Dept. Agr. Tech. Bui. 81 : 14, 1928. 



DESCRIPTION 



Pseuderimerus mayetiolae is more closely related to Ditropinotus 

 aureoviridis Crawford than to any of the other parasites of the hes- 

 sian fly, but it is readily distinguished from that species by its more 

 slender and differently shaped funicle joints, the shorter ovipositor 

 sheaths, the single spur on the hind tibiae, the nonserrated lower 

 margin of hind femora, the much finer and shallower sculpture, and 

 its distinctly different coloration. 



Female. — Length 1.5 to 2 mm. Head viewed from above transverse, a little 

 over twice as broad as thick antero-posteriorly, finely and nearly uniformly re- 

 ticulate-punctate ; ocellocular line equal to a little more than half the post- 

 ocellar line, a little longer than the diameter of an ocellus; temples receding, 

 about equal to half the width of eyes ; occiput slightly concave ; antennal 

 scrobe moderately deep, extending to the front ocellus, its lateral margins 

 rounded ; malar space equal to a little more than one fourth the eye height ; 

 eyes ovate, distinctly pilose ; both mandibles 3-toothed, the inner tooth short 

 and broadly rounded at apex ; labial palpi 3-jointed, short, the apical joint not 

 quite twice as long as broad ; maxillary palpi 4- jointed, the first 3 joints short 

 and subequal, the apical joint as long as the other 3 combined. Antennae in- 

 serted below the middle of head, about on a line with the lower extremities of 

 the eyes, 13-jointed, ciavate ; scape slender, cylindrical ; pedicel rather slender, 

 nearly as long as 5 following joints combined : third joint a true ring joint, 

 the fourth and fifth antennal joints very slightly broader than the ring and 

 no longer ; sixth, seventh, and eighth each broader than long and successively 

 increasing slightly in both length and breadth ; ninth and tenth joints subequal. 

 subquadrate, and a little broader than the preceding joints ; club 3-jointed, 

 distinctly broader than the funicle, about equal in length to the 4 preceding 

 funicle joints, the apical joint terminating in a very short process. Thorax 

 sculptured like the head ; prothorax conical, broader than long, mesoscutum 

 broader than long, the parapsidal grooves complete and distinct ; scutellum 

 nearly as long as mesoscutum, and nearly flat, with a delicate marginal carina 

 apically ; axillae broadly separated ; propodeum short, without lateral folds 

 or spiracular sulci and without a distinct median carina, its sculpture like 

 that of mesoscutum but usually a little stronger. Anterior and posterior 

 femora somewhat enlarged, the latter not serrated beneath ; hind tibiae straight, 

 with a single short apical spur. Wings fully developed, reaching to the apex 

 of abdomen, a little more than twice as long as broad (25:55), bare basally, 

 finely ciliated from base of marginal vein to apex of wing except that an- 

 teriorly the bare area is extended beneath the marginal vein ; stigmal and post- 

 marginal veins subequal, the marginal about twice as long as postmarginal. 

 Abdomen about as long as head and thorax, slightly conic-ovate, finely reticu- 

 lately sculptured, slightly flattened dorsally. the first two or three tergites 

 weakly emarginate medially at apex; ovipositor exserted approximately one 

 fourth the length of abdomen. Head and thorax very dark aeneous, or black 



