64 THE CANADIAN ENTOMOLOGIST. 



the shade of the encroaching wood, we find the Brakes tenanted by 

 inqucesita and pterisii, the Speedwell with its seiata, the Iron weed with 

 cerussata in its crown. In the deeper shadows Collinsonia Canadensis 

 shelters both astuta and duplicata. If fortunate in the locality, the 

 Heraclcum lanatum may contain Harrisii. A little farther up the bed of 

 the ancient stream, if a Sphagnum bog has formed, there may lurk in the 

 Pitcher plants the glorious appassionata. When such localities have 

 escaped the torch for a number of years, more Papaipcma species may be 

 found there to the square yard than in any other territory. 



In the perpetuation of species, "survival of the fittest" may have its 

 place among the higher animals and elsewhere, but among insects, and 

 with maritima in particular, we are impressed with what is rather a sur- 

 vival of the most fortunate. The casualties from parasitism, disease and 

 depredations of enemies of one sort and another bring the fatalities up to 

 an alarming percentage. But after all, if the progeny of a single pair 

 amounted to more than another pair in the genera! outcome, we should 

 soon have to do with pests rather than the elusive and long-overlooked 

 occurrences of our Papaipcma species. With the one under consideration 

 the mode of larval habit lends nicely to such study, and this question of a 

 balance in nature is admirably demonstrated. It, of all the congeners, 

 shows the least disposition to ever leave its burrow, and, as it is so easily 

 located in the conspicuous gall, it is not difficult to tell just how many of 

 a certain locality and brood attain maturity or fall to eventualities. The 

 question how many ova may have been deposited there and escaped the 

 mites, which destroy such numbers shortly after they are laid in the fall, 

 or have survived other vicissitudes of the winter period, to ultimately give 

 up their larvae, is only problematical. From the moment a larva locates 

 in a plant we know it, and it is easy to figure out the average which 

 mature, and this is surprisingly small. 



Of parasites, the most abundant is a Hymenopteron, a species of 

 Hemiteles, which attacks many of the other species as well, most notably, 

 perhaps, nitela And pterisii. Occurring with it is a wingless form of some 

 Pezomachus species, whose presence with the former was a surprise. The 

 Hemiteles larvae attain maturity as the host-larva reaches the last moult, 

 causing it to succumb before pupation. The parasites at maturity pierce 

 the skin of the host and immediately spin up a tough, brownish cocoon, 

 of elliptical form, longitudinally creased and about three millimetres in 

 length. From 30 to 40 usually infest one host, and all emerge and spin 



