OF WASHINGTON, VOLUME XIV, 1912. 91 



the pinkish tinge of the healthy larvae. On May 11 a small 

 parasitic larva appeared on the surface of this individual, 

 having evidently emerged from its host just previously. This 

 was at about 8 o'clock in the morning. Chancing to observe 

 the parasite a few hours later I was amazed to find that it 

 had in that short period at least doubled in size. By 5 o'clock 

 the parasite larva had at least trebled in size since first ob- 

 served in the morning and the host had been reduced to a 

 pellet of skin pushed to one end of the cocoon. This rapid 

 enlargement seems to be more in the nature of engorgement 

 than of development. The parasite larva had begun its 

 cocoon on May 12, at 8 a. m., about 24 hours after emerging 

 as ;i small larva from its host, the adult appearing on the 24th. 

 It was determined by Mr. Viereck as Ascogaster carpocapsa 

 Yier., a braconid of the subfamily Cheloninae. 



A similar habit was a little later observed in the larvae 

 of a chalcid of the genus Crototcchns. On May 18 Dr. C. 

 \\'. Hooper handed me a living, but sluggish, full-grown cater- 

 pillar of I\rophila pyramidoidcs. This I kept in a vial on 

 my desk for observation. On May 23 the larva? of the para- 

 sites appeared, emerging through the skin of the host, mostly 

 along the sides. At first the parasitic larvae appeared like 

 very small, shiny, green papillae or drops, as though the host 

 larva had been repeatedly pricked with a fine point and the 

 juices were oozing out. This illusion was maintained if not 

 intensified as the parasites emerged slowly, and appeared to 

 flow down the sides of the host. From the caterpillar in 

 question about 90 parasitic larvae emerged. They were, how- 

 ever, very small, and the host remained in much the same 

 condition as a sphinx larva which is covered with the cocoons 

 of . \p(intt-l('t somewhat shrunken but still retaining its form. 

 But by the next morning, perhaps IS hours later, the chalcid 

 larva 1 had increased several times in si/e and the caterpillar 

 was a mere shriveled skin, only the head shield retaining its 

 original form. 



M will be noted that although the two species in which 

 this peculiar habit of engorgement was observed are widely 

 separated systematically, biologically I hey are alike in at 

 least one respect both are internal parasites which leave the 

 body of their hosts for pupation. In this feature of their life 

 may lie the explanation of the habit of engorging on the 

 fluids of their hosts, the possible reason being the greater 

 ease of escape from the host for the smaller larvae. 



Dr. Howard expressed great interest in Mr. Cushman's 

 observations. He had often seen the characteristic groups 



