PAEASITES HIBERNATING IN BROWN-TAIL WEBS. 275 



a very little as a rule, and the least motion was sufficient to dislodge 

 the egg or young larva of the parasite. 



Oviposition upon any other host was equally unsuccessful, provided 

 that the host was free to move about to any extent, but whenever 

 it was confined within the limits of a cocoon, and was not too large, 

 it usually fell a victim to the parasite. Especially was this true of 

 the hibernating larvae of hymenopterous parasites within their 

 cocoons, and from these the largest and finest Pteromalus were 

 reared. 



If the parasite or hymenopterous larva was very small, as in the 

 instance of the larva of Apanteles, it was very likely to be killed by 

 the Pteromalus in the process of oviposition and, as a common result, 

 her progeny would perish also. 



Evidence to indicate that the female parasite possesses discrimi- 

 native powers which enable her intelligently to select suitable hosts 

 for her young is wholly lacking, and in consequence, when several 

 individuals are given access to a single nest of the brown-tail moth, 

 the chances are that all of them will concentrate their attack upon 

 the few caterpillars which chance to be most readily accessible, to 

 the exclusion of all others. The outcome is one of the manifold 

 phases of superparasitism. The larvse hatching from the superabun- 

 dance of eggs are unable to reach their full development. They may 

 complete their transformations but the adults produced are small, 

 weak, and in extreme instances wholly unfit for further reproduction. 



In the work of rearing the parasite for colonization purposes, no 

 matter how many parent Pteromalus were used, the number of cater- 

 pillars which were parasitized by them would be a -small percentage 

 of those in the nests exposed to their attack, and invariably when 

 more than a few females were used as parents the nests had to be 

 torn open, so as to expose a large number of caterpillars equally. 

 Otherwise the progeny would be so small as to be practically- worth- 

 less for further reproduction, colonization, or anything else. This 

 in itself was sufficient to render Pteromalus of very much less value 

 from an economic standpoint, and the extraordinary avidity with 

 which it attacked the cocoons of other hymenopterous parasites was 

 anything but a point in its favor. Most especially was this true 

 when the life and habits of Apanteles lacteicolor Vier. were taken into 

 consideration. It soon became evident that Pteromalus was pecul- 

 iarly fitted to act as its most dangerous enemy, and since, between 

 the two, Apanteles was much the more promising parasite, it was 

 decided to abandon all further effort toward the introduction of 

 Pteromalus, and the work of rearing was discontinued. 



Some 250,000 larvae and pupae were on hand at the time when this 

 decision was reached, and these were placed in cold storage. It was 

 considered probable that the species was already introduced, if it 



