110 PROC. ENT. SOC. WASH., VOL. 24, NO. 5, MAY, 1922 



the egg of the Hessian fly, and from his description of the habits 

 of the parasite under his observation it was evidently the species 

 Platygaster hiemalis. He briefly recorded observing it oviposit 

 in the egg of the Hessian fly in autumn, and mentioned that four 

 or five eggs were laid in a single egg of the fly, and that the host 

 continued its development but never reached the adult stage. 

 All of these habits conform identically to those of Platygaster 

 hiemalis. In 1847 (2) and again in 1862 (3 Asa Fitch reviewed 

 Herrick's account ot this insect but added no original observa- 

 tions. Herrick's account was again quoted by Packard both 

 in 1880 (4) and in 1883 (5). In these articles the statements 

 of Herrick were assumed to refer to the larger proctotrypoid 

 parasite Platygaster herrickii Pack. 



According to Ashmead (10) Platygaster hiemalis was first 

 reared by Riley in 1876 and again by Forbes in 1888, in which 

 year Forbes published the original description (7). The following 

 year, Riley (8) called att;ntion to Forbes' description, and in 

 1891, (9), he listed the species. Two years later Ashmead (10) 

 incorporated Forbes' description in his "Monograph of the 

 North American Proctotrypidae," and in 1897 the species was 

 again listed by Paul Marchal (11). Osborn (12), in 1898, cited 

 the original description, and in 1899 Lugger (13) recorded finding 

 six cocoons of this parasite in a Hessian fly pupanum. In an 

 article by Webster and Newell (14), published in 1902, this para- 

 site was mentioned as being reared in quantities in Ohio, and 

 in 1906 Tucker (16) discussed the economic importance of this 

 parasite, citing a letter by Webster in which was mentioned the 

 introduction of P. hiemalis from North Dakota into Kentucky, 

 Tennessee, and California. This same year Webster (17) gave 

 a brief discussion of P. hiemalis, and Gossard and Houser (15) 

 mentioned the abundance of P. hiemalis in Ohio. The' follow- 

 ing year Bruner and Swenk (18) referred to P hiemalis in 

 Nebraska, and Webster (19) recounted the great importance of 

 this parasite in control of the Hessian fly and discussed its 

 possible polyembryonic nature. In 1907 (21) he also gave a very 

 interesting economic account of this parasite and related various 

 attempts to introduce it from one part of the country to another. 

 He attributed two generations a year to Polygnotus, but more 

 recent observations have shown that each species normally has 

 but one generation a year. The erroneous conclusion was* 

 undoubtedly due to a confusion of the two species one of which 

 emerges in the spring, the other in the fall. In 1908 C. N. 

 Ainslie (20) gave an account of the parasitism of Polygnotus by 

 Tetrastichus. In so far as this material was taken from wheat 

 stubbles collected during July, the species involved was very 

 likely vernalis. In this same article Mr. Ainslie told of the at- 

 tempted introduction of Polygnotus into Sharpsburg, Md., con- 



