THE CANADIAN ENTOMOLOGIST. 135 



back of 2nd and 3rd segments, near the junction, and at the second lar- 

 val stage), and as the grubs hatch they eat their way into the larva, to 

 emerge when both they and the larva are full grown — of course, destroying 

 the latter. Another is Hymenopterous and minute. Its egg is deposited 

 in the very young larva, probably at first stage. The grub eats out when 

 the larva is half grown, at once spins a silken cocoon, from which in a few 

 days the new parasite comes forth. The destruction of larvae by these, 

 and very likely, other similar parasites, is immense. Of about a dozen 

 mature larvae received from Prof. Comstock, but one reached chrysalis, 

 all the rest giving out one of the Diptera spoken of. If any parasite 

 attacked the mature larva, the grub of the former would live within and 

 destroy the chrysalis, and instead of a butterfly therefrom, the parasite 

 would emerge. Multitudes of chrysalids of other species of butterflies 

 are thus destroyed ; but in pseudargiolus there appears to be a singular 

 immunity from enemies at this stage. I have never yet seen a parasite 

 emerge from a chrysalis. Why this species, and doubtless many other 

 Lycaouc. are thus favored will perhaps in some degree appear from a little 

 incident to be related. On 20th June, in the woods, I saw a mature larva 

 on its food-plant, and on its back, facing towards the tail of the larva, stood 

 motionless one of the larger ants designated above as the third in size). 

 At less than two inches behind the larva, on the stem, was a large ichneu- 

 mon fly, watching its chance to thrust its ovipositor into the larva. I bent 

 down the stem and held it horizontally before me. without alarming either 

 of the parties. The fly crawled a little nearer and rested, and again 

 nearer, the ant making no sign. At length, after several advances, the 

 fly turned its abdomen under and forward, thrust out its ovipositor, and 

 strained itself to the utmost: to reach its prey. The sling was just about 

 to touch the extreme end of the larva, when the ant made a dash at the 

 fly, which flew away, and so long as I watched — at least live minutes — did 

 not return. The larva had been quiet all this time, its tubes out of sight 

 and head buried in a flower bud, but the moment the ant rushed and the 

 fly fled, it seemed to become aware of the danger, and thrashed about the 

 end of its body repeatedly in great alarm. But the tubes were not pro- 

 truded, as I wis clearly able to see with my lens. The ant saved the 

 larva, and it is probable that ichneumons would in no case get an oppor- 

 tunity to sting so long as such vigilant guards were about. It strikes me 

 that the larvae know their protectors, and are able and willing to reward 

 them. The advantage is mutual and the association is friendly always. 



