SERPHOID AND CHALCIDOID PARASITES OF THE HESSIAN FLY 95 



The species is normally a solitary, primary, external parasite. Its 

 eggs are laid in the hessian-fly flaxseed and, according to Packard, 

 hatch in from iy 2 to 14 days, depending upon the temperature. 

 In his laboratory experiments Packard found that larvae reared 

 in glass cells required 7 to 11 days to complete their larval develop- 

 ment and that after completing their larval growth the majority 

 of these remained quiescent for months. Pupation takes place as a 

 naked pupa within the fly puparium, and the pupal period is said 

 to occupy from 7 to 14 days. 



The seasonal history of the species has not been thoroughly 

 worked out. According to Packard it was found in the larval stage 

 in Kansas in March. Forbes reports that the earliest emergence 

 observed by him was June 3. Dated specimens in the series studied 

 by the writer, however, indicate emergences as early as April 6 and 

 ranging from that date through all the following months to October. 

 In all probability there are at least 2 or 3 generations per year. 



DISTRIBUTION 



This species is recorded in Europe from England, France, and 

 Russia, the distribution in Russia, according to Lindeman, extend- 

 ing from the government of Vologda in the north to that of the 

 Don Cossacks on the shores of the Black Sea. These records indi- 

 cate the probable occurrence of the species over the entire wheat- 

 growing region of Europe, despite the fact that it has not been 

 recorded, so far as is known, from any of the central European 

 countries. 



In North America it is almost certainly present wherever the fly 

 occurs. Fletcher has recorded it from Manitoba and Prince Ed- 

 ward Island, Canada, and the writer has seen specimens from On- 

 tario, Canada, as well as from practically every wheat-growing State 

 in the United States from Vermont and North Carolina to Cali- 

 fornia, Oregon, and Washington. 



In the United States National Museum collection is a single male 

 specimen of this species, the label of which shows it to have been 

 reared from wheat straw from Tunis, Africa. Nothing further is 

 known of the history of this specimen. 



IMPORTANCE 



This is undoubtedly one of the most important of the hessian-fly 

 parasites. According to Hill and Smith it ranks fourth in effec- 

 tiveness among parasites of the fly in the eastern part of the United 

 States, being outranked by two of the Platygasters and Eupelmus 

 allynii. In California it is probably of more importance because 

 of the absence from that section of both Platygaster hieinalis and 

 P. zosine. 



MERISUS FEBRICULOSUS Girault 



(Fig. 21) 



Merisus isosomatis Webster, lLS.Dept.Agr., Div. Ent., Insect Life 5 : 90, 1892 ; 

 Viereck, in Smith, Insects of New Jersey . . ., p. 642, 1910; Viereck, Conn. 

 State Geol. and Nat. Hist. Survey Bui. 22 : 478, 1916. 



Stictonotus isosomatis Webster. U.S.Dept.Agr., Bur. Ent. Bui. (n.s.) 42:22. 

 1903; Ent. Soc. Wash. Proc. 7: 115, 1905; U.S.Dept. Agr., Bur. Ent. Circ. 66: 4, 

 1908 ; Kelly, Jour. Econ. Ent. 3 : 202-204, 1910. 



