14 MISC. PUBLICATION 17 4. U.S. DEPT. OP AGRICULTURE 



HOSTS AND LITE HISTOEY 



Platygaster zosine is a primary, internal, gregarious parasite of 

 the hessian fly in North America and in Europe. It is also recorded 

 as a parasite in Europe of (G ecidomyia) Mayetiola avenae Marchal. 

 The egg of the parasite is laid in the egg of its host and development 

 of the germ is polyembryonic. The larvae develop in the mid intes- 

 tine of the host larvae and when fully grown pupate in individual 

 sacs or cells closely grouped together within the dead body of the 

 host larva or pupa. Adults emerge early in the spring and attack 

 the eggs of the spring generation of the fly. The larvae develop 

 rapidly, pupate in late July, according to Hill, and reach the adult 

 stage early in August. The adults normally do not emerge at this 

 time, however, but remain in their pupal cells during the fall and 

 winter and emerge the following spring. The species is said to be 

 capable of reproducing parthenogenetically. 



DISTRIBUTION 



In Europe Platygaster zosine is known only from London in 

 England and from the Department of Loir-et-Cher in France. In 

 all probability its distribution is much wider than these few records 

 indicate. In North America it is generally distributed throughout 

 the winter-wheat-growing region from Xew York to Missouri and 

 south at least to Staunton. Va. The writer has seen no specimens 

 from points west of Missouri. 



IMPORTANCE 



This species is probably the most important parasite of the spring 

 generation of the fly in North America. In the Middle Atlantic 

 States it is said by Hill to destroy an average of 23.89 percent of this 

 generation of the fly each year. In Europe very little seems to be 

 known of its effectiveness. 



PLATYGASTER HERRICKII Packard 



(Fig. 3) 



Platygaster herriekii Packard. Rpt. U.S. Ent. Comm.. Bui. 4: 21. 1880, and U.S. 

 Ent. Comm. Rpt. 3: 220, 1S83 ; Riley, U.S. Natl. Mns. Proc. (1885) 8: 420. 1886; 

 Packard, Amer. Nat. 19 : 1104, 1885 : Riley. Amer. Assoc. Adv. Sci. Proc. 34 : 333. 

 1886; Askniead. Canad. Ent. 19: 132, 1887; Cresson, Synopsis of tke families 

 and genera of tke Hymenoptera of America, nortk of Mexico . . ., p. 250. 1887 ; 

 Lindeman. Bui. Soc. Imp. Nat. Moscou (2) 1: 178, 192, 1887; Forbes. Psycke 5: 

 40. 1888 : Enock. Ent. Soc. London. Trans. 1888, proc. xxiii ; Riley, U.S.Dept.Agr.. 

 Div. Ent.. Insect Life 4 : 125. 1891 ; Askmead. U.S. Natl. Mus. Bui. 45 : 324. 1893 ; 

 Howard, U.S.Dept.Agr., Div. Ent.. Insect Life 7: 415. 1895: Marckal. Ann. Soc. 

 Ent. France 66 : 81, 1897 : Kulagin. Ztsckr. Wiss. Zool. 63 : 196-232. 1898 ; Osborn, 

 U.S.Dept.Agr. Div. Ent. Bui. (n. s.) 16: 28. 41, 35, fig. 6, 1898; Dalla Torre, 

 Catalogues kymenopterorum .... v. 5. 473, 1898; Felt. N.Y. State Ent. Rpt. 17 

 (Mus. Bui. 53) : 721, 1902: Stedman. Missouri State Bd. Agr. Rpt. 34: 83. 1902: 

 Webster, U.S.Dept.Agr.. Bur. Ent. Circ. 70: 12. 13. fig. 13. 1906; Webster. U.S. 

 Dept. Agr. Yearbook 1905 : 634. 1906 : Gossard and Houser, Okio Asr. Expt. Sta. 

 Bui. 177: 31, 33, 1906: Marckal. Arck. Zool. Expt. et Gen. (4) 4: 490, 1906: 

 Webster. U.S.Dept.Agr., Bur. Ent. Bui. 67: 96. 1907: Brunei* and Swenk, Nebr. 

 Agr. Expt. Sta. Bui. 96 : 16. fig. 3. 1907 ; Viereck. in Smitk. Insects of New Jersey 

 . . ., p. 2, 652. 1910; Felt, N.Y. State Ent. Rpt. 28 (Mus. Bui. 165) : 40. 1913: 

 Headlee and Parker, Kans. Agr. Expt. Sta. Bui. 188: 110. 1913; Webster, 

 U.S. Dept. Agr. Farmers' Bui. 640: 16. 19, 1915: Fyles, Ontario Ent. Soc. Rpt. 

 40 : 56, 1916 ; Viereck, Conn. State. Geol. and Nat. Hist. Survey Bui. 22 : 540, 1916 ; 



