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



appearance of fine transverse rugulae; head apparently bare except for a few 

 hairs on clypeus and mandibles ; antennae 10-jointed ; scape extending above 

 the vertex, about as long as the following 61 antennal joints combined, reticu- 

 lately sculptured ; pedicel two to two and one half times as long as thick, 

 as long as the 2 following joints of the flagellum or slightly shorter ; first and 

 second flagellar joints subequal in length and very slender, cylindrical, closely 

 joined ; third and fourth flagellar joints very slightly thicker than the preced- 

 ing joints, distinctly separated, subequal, shorter than the other joints, usually 

 a little longer than broad, and more or less subtriangular in profile; club 

 4-jointed, the joints well separated, nearly pedicellate, each longer than broad, 

 much thicker than the preceding joints, the apical joint somewhat longer but 

 rarely thicker than the other club joints ; whole flagellum sparsely clothed with 

 rather short hairs. Thorax ovoid, about as broad at tegulae as thick dorso- 

 ventrally ; pronotum weakly reticulated, shining, bare ; mesoscutum bare, weakly 

 reticulated, and shining, the reticulation frequently appearing as longitudinal 

 lines ; parapsidal grooves absent ; scutellum shining, sparsely hairy, convex, 

 about as broad as long, more or less distinctly carinately margined laterally 

 at base but not at apex, the groove separating it from mesoscutum deep and 

 broadest laterally ; propodeum short, medially with two longitudinal carinae 

 which diverge posteriorly, the area between the carinae smooth and bare, laterad 

 of the carinae with moderately dense white pile ; mesopleura bare and mostly 

 smooth, but with some longitudinal rugulae beneath the wings ; metapleura 

 covered with dense whitish pile. Abdomen approximately as long as the thorax, 

 ovate ; first tergite much broader at apex than long down the middle, with a 

 smooth bare knob at base, otherwise covered with pile; second tergite com- 

 prising two thirds or more of the total length of abdomen, its extreme base 

 weakly sculptured and covered with white pile, elsewhere smooth and bare, 

 with the two basal sulci rather broad and short ; tergites beyond the second 

 short, smooth, and nearly bare; ovipositor concealed. Legs rather long and 

 slender, the tarsi all distinctly longer than their tibiae. Fore wings unusually 

 long, equal to about three times the length of abdomen, nearly uniformly 

 ciliated from base to apex, the marginal cilia equal to approximately one sixth 

 the wing width ; hind wings also long and rather narrow. Color shining black ; 

 mandibles, trochanters, and tarsi usually dark reddish ; antennal flagellum 

 black with a somewhat reddish cast ; wings with a distinct fuscous cast. 



Male. — Length 0.7 to 0.9 mm. Antenna a little longer and more hairy than 

 in the female, the pedicel not so long as first and second flagellar joints ; the 

 first flagellar joint distinctly shorter than the second, which is nearly as long 

 as the pedicel and usually thicker than either the preceding or the following 

 joint; third and fourth flagellar joints not equal, the fourth distinctly the 

 longer ; fifth, sixth, and seventh flagellar joints subequal, and each usually 

 fully twice as long as thick; apical joint longest of the flagellar joints, about 

 four times as long as thick, and usually a little narrower than the preceding 

 joint ; abdomen more broadly rounded than in the female. Otherwise like the 

 female. 



REVIEW OF LITERATURE 



Francis Walker described Platygaster zosine in 1836 from a male 

 specimen taken near London, England. Walker's description, al- 

 though short and incomplete, agrees in every particular with that of 

 the insect described above and includes the most striking characters 

 which differentiate it from related forms, viz the transversely rugu- 

 lose frons, the inconspicuous parapsidal grooves, and the infuscated 

 fore wings. 



In 1897 Paul Marchal recorded Polygnotus zosine and P. minutus 

 Lindeman as parasites of Phytophaga destructor in France. The 

 identifications were made for Marchal by Ashmead, who, during the 

 same year, published the results of his study of the material. Mar- 

 chal gave an account of the development of the so-called P. minutus, 

 and in 1903 and again in 1904 he further discussed the same subject, 

 showing clearly the polyembryonic nature of its development. Of 



