THE CANADIAN ENTOMOLOGIST. 81 



TRICHOGRAMMA PRETIOSA, RILEY: COLOUR VARIA- 

 TION IN THE ADULT, WITH DESCRIPTION OF 



A' NEW VARIETY. 



BY A. ARSENE GIRAULT, WASHINGTON, D. C. 



In the original description of tliis insect,* Dr. Riley says that on 



account of its uniform pale yellow colour it is easily distinguished from 



Trichogramma miniitinn, Riley, which is black. Unfortunately, this does 



not hold.t Out of the hundreds of specimens of pretiosa reared during 



the entire season of 1904, at Paris, Texas, from the eggs of Heliothis 



obsoleta, Fabricius, there appeared from a lot of host eggs on Sept. 20th 



a number of dark individuals, which could easily have been mistaken for 



a distinct species. Previous to this, all of the individuals had been 



normally coloured. 



The origin and subsequent history of this variety is as follows: 



On the loth, iith and 12th of September a generation of 11 males 



and 22 females, all normally coloured, emerged in confinement from the 



host eggs on tomato leaves brought in from the field. Sixty-four eggs 



from moths in confinement were then supplied them on Sept. iith, and 



freely parasitized. As a result, there emerged from these parasitized eggs 

 a second generation of 53 males and 58 females, plus 11. 



This second generation varied considerably, some of the individuals 

 were very dark, others wholly black. The variation consisted in very 

 light brown to a deep black, and gradations were present from one 

 to the other. In the latter, the black first appeared in the abdomen, and 

 as the variation became greater extended to the thorax and head, until 

 the whole body became black. In this generation the variety was present 

 in the proportion of i to 7. Both the typical specimens and the variety 

 were freely copulating with each other. 



The adults of this second generation were supplied with 48 fertile 

 host eggs from moths kept in confinement, on Sept. 21st. Oviposition 

 took place, and as a result a third generation began to appear on Sept. 

 30th. This generation consisted of 47 adults, of which 7 males and 7 

 females were the black variety. 



'Canadia.v Ent., 1879, XL, pp. 161-162. 



tDyar, 1893, 

 he dorsum of 



March, 1906 



tDyar, 1893, Canadian' Ent., XX\'., p. 256, mentioned that the males oi pretiosa are often black 

 on the dorsum of the abdomen. 



