1885.] PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 421 



her antennae, and when found intrudes the fatal egg, wliich I find takes three-fourths 

 of a minute, full three times as long as it takes the Hessian Fly. The little parasite 

 is much longer, too, in finding the eggs than the fly is in laying them. I find that 

 each egg receives one, two, or three of the parasite's eggs. The eggs of these latter 

 are tardy in hatching, so that the larva of the parasite may feed on the maggot of 

 the Hessian Fly, not her eggs. These pupate in the puparium of the fly."* 



Dr. Packard considers it probable that this insect is the same species 

 as Herrick mentions and speaks of as follows : 



"The insect is'abundaut in the autumn. I first saw it September 23, 1833, in the 

 act of deijositing its eggs in the eggs of the Hessian Fly.' From subsequent observa- 

 tions it appears that four or five eggs are laid in a single egg of the Hessian Fly. The 

 latter egg hatches, and the animal advances to the pupa state as usual, but from 

 the puparium no Hessian Fly ever comes forth. The parasite forms within the pupa- 

 rium a silky cocoon of a brownish color. "t 



There is probably some error in the above recorded observations. It 

 is contrary to all precedent, as remarked by Mr. Howard in a note to 

 page L'19 of Dr. Packard's article, just quoted, that a female Platygaster 

 should oviposit in an egg, and, even allowing such a possibility, it is 

 highly improbable that an Qgg so pierced would hatch and the Platy- 

 gaster imago issue only from the coarctate Cecidomyia larva, as para- 

 sitized eggs so far as we now know do not hatch. We should be slow to 

 reject asserted observation, however opposed to geiieral rule, but in 

 this case verification is very desirable on account of the soft nature of 

 the Cecidomyia egg and its general resemblance to the young larva. 



The twenty-two specimens of this species which I have studied were 

 all bred in March, 1884^ from the puparia of the Hessian Fly which were 

 received in August, 1883, from Mr. Barlow, of Cadet, Mo. 



The Hessian Fly in Europe is also parasited by one or more species of 

 the genus Platygaster^ and Dr. Packard has received specimens, which 

 I have examined, from Prof. Ferdinand Cohn, of Breslau. These are 

 so badl> mutilated, however, that nothing more than the genus could 

 be determined. It is evidently a different species from PI. lierricMi and 

 is considerably smaller. 



It will be unnecessary to give a detailed description of herricMi, as 

 ])r. Packard has already decribed it at length in Bulletin 4 of the United 

 States Entomological Commission, and also in the third report of the 

 commission. The description is recognizable, but the figure given in 

 both of these reports is taken from Fitch, and is so poor that I have 

 had a new figure made (PI. XXI, Fig. 6). 



A single female Tetrastichus was sent to me last June as a parasite 

 of the Hessian Fly, by Prof. S. A. Forbes. It differs from T, prodiictus, 

 and he has given it the indistinctive MS. name of carinatus, but there 

 js the same question as to whether it is a primary or secondary parasite 

 which I have raised in speaking of productus. It is smaller than pro- 



*Sixteenth Annual Report of the Secretary of the State Board of Agriculture of the 

 State of Michigan (1877), p. 375. 

 t American Journal of Science and Arts, xli, 153-158 (October, 1841). 



