162 PARASITES OF GIPSY AND BROWN-TAIL MOTHS. 



supposition that there were parasites which attacked them as soon 

 as they resumed activity in the spring, and left them before they 

 reached their last stage. There are, indeed, several species which 

 have such habits, but there is none amongst them which may not be 

 secured equally well from either the hibernating caterpillars or from 

 the full-fed and pupating caterpillars, or from both. In consequence 

 the importation of partly grown caterpillars in the spring has never 

 been attempted except experimentally. 



Of the considerable number which has been received, nearly all 

 have been packed in the same manner as are the full-fed caterpillars. 

 They are nearly always alive on receipt, and usually feed voraciously 

 when given an opportunity. Undoubtedly a considerable percentage 

 contains parasites of those species which only emerge after the cocoon 

 is spun, but every attempt to rear these parasites by feeding the cat- 

 erpillars has resulted in failure. They will feed once, at least, but 

 usually not more than a few times, and then die sooner than would 

 have been the case had they not fed at all. Some among them will 

 live for a long time, feeding a little but scarcely growing at all, and 

 sometimes a very small percentage will complete growth and pupate. 

 The percentage is so very small, however, and the labor and pain of 

 handling the caterpillars is so great, as to render the work of feeding 

 them of much more than doubtful economy, in every instance in 

 which it has been attempted. 



FULL-FED AND PUPATING CATERPILLARS OF THE BROWN-TAIL MOTH. 



The temptation is strong to use the present opportunity for the 

 purpose of giving vent to certain poorly suppressed and heartfelt 

 expressions of opinion concerning the infliction known euphemisti- 

 cally and very inadequately as the brown-tail "rash." It is a very 

 living subject of discussion during most of the year at the laboratory, 

 but never more so than while the boxes of full-fed and pupating 

 brown-tail caterpillars are being received from Europe. 



Aside from the fact that the handling of this sort of parasite mate- 

 rial has been productive of most acute physical anguish, it has been 

 altogether the most uniformly satisfactory of any received. No mod- 

 ifications in the methods of packing have been suggested during the 

 past five years, other than a slight modification in the form of the box 

 in order to alleviate the trouble to which reference is made above. 



Rather shallow boxes, having a capacity of about 50 cubic inches, 

 are used for the purpose. (See PI. VIII,^figs. 1,2.) The caterpillars 

 are collected, preferably just before they spin their cocoons, and 100 

 are placed in each box, together with a few twigs with foliage at- 

 tached, which serve less as food than as a support for the cocoons. 

 When collected at the proper time practically all will spin and pupate 



