SEKPHOID AXD CHALCIDOID PARASITES OF THE HESSIAX FLY 141 



REVIEW OF LITERATURE 



Tetrastichus carinatus was described by Forbes in 1885 from speci- 

 mens reared by him from wheat stems infested with the hessian fly 

 collected at Anna, 111. At nearly the same time Riley published 

 the description of T. productus Riley. In connection with his de- 

 scription, Riley mentioned the fact that he had received from Forbes 

 a single specimen of T. carinatus, and he pointed out several differ- 

 ences between his own species and the one of Forbes. Riley's re- 

 marks were reviewed later in the same year in the American Natu- 

 ralist and in the Proceedings of the American Association for the 

 Advancement of Science. Osborn reproduced Forbes' description 

 in his bulletin on the hessian fly in 1898. In 1901 Sanderson re- 

 corded T. carinatus as a parasite of Dasyneura leguminicola (Lintner ) 

 in Delaware. Ainslie published a short note in 1908, in which he 

 figured a puparium of the hessian fly parasitized by a Platyg aster 

 with one of the Platygaster pupation cells occupied by an unidenti- 

 fied species of Tetrastichus. This Tetrastichus is now believed to 

 have been T. carinatus. In 1909 Folsom recorded the rearing of 

 two unidentified species of Tetrastichus from Dasyneura legumini- 

 cola, the clover seed midge, in Illinois and incidentally mentioned 

 that Sanderson had reared T. carinatus in Delaware in 1900 from 

 the same midge. In 1913 Felt stated that T. carinatus was abundant 

 as a parasite of the hessian fly in Xew York, and in 1928 Hill and 

 Smith discussed the species in their paper on the relative abundance 

 of hessian-fly parasites in the eastern part of the United States. 



Two years after the description of T. carinatus and T. productus, 

 there appeared the description of Tetrastichus rileyi Lindeman, 

 based upon specimens reared from the hessian fly in Russia. Linde- 

 man compared this species with productus Riley, pointing out cer- 

 tain distinguishing characteristics. He did not separate it from 

 carinatus, although he mentioned that species in a footnote. Miss 

 Ormerod submitted to Lindeman specimens which she had reared 

 from the fly in England, and he identified them as T. rileyi. At 

 nearly the same time, Riley also studied material reared from the 

 fly in England, and in it he. too. found specimens which he iden- 

 tified as T. rileyi. Blunck has recently recorded T. rileyi as a para- 

 site of Mayetiola phalaris in Pomerania. German} 7 . 



In the Xational Museum collection are the remains of five speci- 

 mens mounted with minuten pins on a single piece of cork and bear- 

 ing the label " Tetrastichus rileyi Ldm." in what is believed to be 

 Lindeman's own handwriting. These specimens bear no locality or 

 other label except the name label, but L. O. Howard has assured the 

 writer that they were received from Lindeman and that in all proba- 

 bility they represent a part of the type material. Only parts of 

 these specimens now remain, but enough to permit the positive state- 

 ment that T. rileyi is identical with T. carinatus. This opinion is 

 confirmed by a single well-preserved specimen reared from the hes- 

 sian fly in Russia by T. Cheviroff , apparently at St. Petersburg 

 (now Leningrad), which is not only identical with what remains of 

 the Lindeman specimens Of T. rileyi but is also in every respect a typi- 

 cal representative of T . carinatus. Three additional specimens in 

 the collection which belong to the species carinatus are from Eng- 

 land, dated May 23, 1894. 



