226 PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 



This is one of the less striking of several examples of a species which 

 differs from another in biological rather than in structural charac- 

 teristics. Others are to be found in the European race of Tricho- 

 gramma, in the Japanese Apanteles parasitic upon Euproctis con- 

 spersa, which so resembles the brown-tail Apanteles of Europe, or in 

 Parexorista chelonix, examples which will be again referred to on 

 subsequent pages. 



The large, flattened, and conspicuous eggs characteristic of Tachina 

 and its allies are the most, and in fact the only familiar type of tachinid 

 eggs, and they are deposited before embryological development has 

 taken place in at least a part of the instances which have come under 

 direct observation. The larva issues through an irregular hole in one 

 end, and immediately forces an entrance through the skin of its host. 

 The life cycle is longer than in the case of Compsilura, but just how 

 much longer is not known. Sometimes the larva is carried over into 

 the pupa of its host, but not very often. Very frequently it kills the 

 host after it has prepared for pupation. Nearly always it leaves the 

 host remains before pupating, on its own account, but occasionally # 

 pup aria within the caterpillar skin or pupal shell are found. 



The puparium (PI. XX, fig. 2), unfortunately, is practically insepa- 

 rable from that of Tricholyga grandis or Parasetigena segregata in its 

 structural details, so that it is necessary to rear the fly before the spe- 

 cies can be determined. 



As a parasite of the gipsy moth, Tachina larvarum may and some- 

 times does take preeminent rank. Caterpillars from Holland have 

 been received from which more pup aria were secured than there were 

 hosts, and the same has occurred on at least one other occasion in the 

 instance of a box of caterpillars from Italy. When Tricholyga grandis 

 is common, Tachina larvarum is rare, or at least has been rare in each 

 instance in which the two species have been specifically determined 

 as they issued from the imported material. It has also been entirely 

 absent from some lots of caterpillars which did not produce Tricholyga. 



It was about the first, if not the very first, parasite to be received 

 alive in the course of the parasite-introduction work, and mention 

 will be found in Mr. Kirkland's first report as superintendent of moth 

 work, of .its having been reared from Italian material in 1905. It was 

 not secured in sufficient abundance to make colonization possible 

 until 1906, but in that year quite a number of small colonies was 

 planted in various localities in the infested territory. In 1907 it was 

 received, but in not such large numbers, and still smaller numbers 

 were secured and colonized in 1908. In 1909, for the first time, really 

 satisfactory colonies were planted, and one of these colonies was 

 strengthened by the liberation of more individuals in 1910. 



So far as it has been possible to determine, no results followed these 

 several attempts at colonization. Of all of the tachinids liberated in 



