TRANSPORTATION OF USEFUL PARASITIC INSECTS. 



The idea of rearing the useful parasitic insects, and of transporting 

 them, when necessary, from one part of the country to another, has 

 often presented itself to practical entomologists, and was a favorite 

 topic of speculation of my predecessor in office, B. D. Walsh. But the 

 very small size of most of these insects, many of them, indeed, being 

 so minute that they cannot be easily seen without the aid of a lens, and 

 the consequent difficulty of manipulating them, have always given a 

 somewhat chimerical aspect to the suggestion, and have caused it to be 

 regarded as more ingenious than practicable. 



In the course of our investigation of the Oyster-shell Bark-louse of 

 the apple tree, in the year 1870, we discovered a minute Chalcis fly, 

 wliich we designated as the Chalcideous iiarasite of the Oyster-shell 

 Bark-louse, f Chalcis [A2)heU'nufi\ mytilaspidisj which was found to be 

 extensively instrumental in extirpating that deadly enemy of the apple 

 tree, by boring into the scale and depositing her own egg in the body, 

 or in the midst of the eggs of the Bark-louse. The parasitic larvjie 

 which hatched from this egg lived at the expense of the Bark-lonse 

 and its eggs, and thus caused their destruction. It was found that in 

 several of the counties of this State where the examinations were made, 

 that more than half of the bark-lice had been destroyed by this jiara- 

 site, its operations being known, partly by the presence of the little 

 grubs beneath the scales, and partly by tlie miniTte roimd holes in the 

 scales, through which the Chalcis-liies had escaped. It was also found, 

 by examining the scales late in the fall, that one brood of the Chalcides 

 hibernated in the larva state beneath the scales. The idea, therefore, 

 readily occmred that this was a very favorable opportunity for testing 

 the i)racticability of transporting these friendly parasites to those parts 

 of the country in which their presence cannot now be detected. We 

 had previously received several packages of apple twigs from dif- 

 ferent localities in the northern i)art of Illinois and the southern part 

 of Wisconsin, heavily infested with the scales of the Bark-louse, but 



