February, '15] CHAPMAN AND GLASER: WILT DISEASE _ 145 



Distribution- — Group B 



The insects contained in this group are reported on the authority of 

 European investigators, who in the course of their studies of the 

 disease of the Nun moth and silkworm caterpillars, either found 

 a similar disease in these other species or by inoculation with the 

 virus of diseased Nun or silkworms produced a similar condition in 

 them. 



Though details are generally lacking, enough information, in case 

 of the majority of the caterpillars, is given to dispel any doubts one 

 may have that the observers were not dealing with true polyhedral 

 diseases. However, in regard to the production of the polyhedral- 

 sickness in the larvae of beetles and flies we do not feel so confident. 

 Without going into too minute detail w^e should like to know whether 

 the wilt ever occurs in these insects naturally. Also if all the typical 

 sj^mptoms are manifested in these individuals as in caterpillars. Until 

 this and other more detailed information is forthcoming, we cannot 

 come to any decision on the matter, further than to say all our own 

 efforts in this direction have resulted negatively. 



Distribution — Group C 



We believe the species in this group should be reported at this time 

 because they are all of more or less economic importance and particu- 

 larly because they have a caterpillar malady which has checked them 

 considerably, if not completely controlled them at some time or other. 

 The various observers who have worked on. the life histories and habits 

 of these pests or have studied some special outbreak of them have 

 made special mention of these maladies and their possible importance 

 as factors in controlling these pests. 



In looking over the histories of these diseases and in some instances 

 getting the information at first hand from the investigators themselves, 

 we were impressed with the similarity of many of them to wilt. With 

 the exception of Colias philodice, we have not examined any diseased 

 caterpillars of this group. A few Colias caterpillars which we tried 

 to infect by feeding them army worm wilt died. They did not 

 show the typical wilt symptoms. However, on examination a few 

 polyhedra were found. We are incKned to believe that their presence 

 in the Colias caterpillars was due to the unsatisfactory manner of 

 feeding. Some of the material may have dried on the skin of the 

 caterpillars. It was then washed off when the caterpillars were crushed 

 for examination. Until this experiment is repeated several times or 

 the wilt is found naturally in this species we cannot accept these results 

 ■3iS final. 

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