ENTOMOLOGICAL SOCIETY OF ONTARIO. 89 



In percentages the result may be expressed as follows : 



Per cent. 



Moths 21 07 



Dipterous parasites „ 22.02 



Hymenopterous parasites 1 1 02 



Disease. 3.58 



Total 57.69 



This leaves about 2,000 chrysalids dead from causes not yet ascertained. From 

 careful examination of a small proportion of them it seems probable that from 400 to 

 500 have been killed by parasites which have died without emerging. There still remain 

 also about 200 dipterous puparia in the rearing cage?, from which the adults may still 

 emerge. That the majority of the remainder have died from disease seems probable. 

 The mortality ratio was, therefore, 79 per cent., as against 98.2 per cent, at a corres- 

 ponding time last year ; and, while last year hymenopterous parasites were responsible 

 for nearly the whole of the mortality, this year they brought about not more than 15 per 

 cent. 



These additional observations only accentuate the extraordinary features of the 

 parasitism of this lepidopterous insect. The multiplicity of factors upon which its 

 increase and decrease depend and the important interrelations of the species concerned 

 are astonishing to one who has not especially studied this phase of insect life. 



TEMPERATURE EXPERIMENTS AS AFFECTING RECEIVED IDEAS ON 

 THE HIBERNATION OF INJURIOUS INSECTS. 



It is a well-known fact among agriculturists and horticulturists that winter weather 

 of a steadv degree of severity is more favorable to plant growth than an open winter with 

 alternating freezes and thaws. With regard to certain injurious insects it has become an 

 accepted idea among economic entomologists that this same principle will hold, yet the 

 question comes to all of us from farmers and others with a considerable degree of fre- 

 quency as to whether a given winter which has been unusually severe will not have resulted 

 in the destruction of injurious insects to such an extent as to promise comparative immu- 

 nity the coming season. We have been obliged, or at least the writer has been obliged, 

 to answer such questions theoretically. There has been no exact experimentation, so far 

 as he is aware, along this line. It is, therefore, with pleasure that he calls attention 

 to the results of recent experimentation by Dr. Albert M. Read, of Washington, the 

 manager of the cold storage department of the American Security and Trust Company, 

 and the same gentleman who conducted the experiments on the effect of cold storage 

 upon household insects referred to in a paper read by the writer before the last meeting 

 of this association. Dr. Read has found in the course of his experiments, which have 

 now extended over two years, that a constant temperature in the neighborhood of 18° F. 

 will not destroy the larvee of Tineola biselliella or of Attagenus piceus, but that an alter- 

 nation of a low temperature with a comparatively high one invariably results in the 

 death of the larvae of these two insects. For example, if larvae of either which have been 

 kept at a temperature of 18° F. are removed to a temperature of from 40° to 50° F. they 

 will become slightly active, and when returned to the lower temperature and kept there 

 for a little time will not revive upon a transfer to the warmer temperature. 



It is thus rather satisfactory to have experimental proof in support of previously 

 accepted but more or less theoretical ideas. 



Mr. Rolfs had noticed that after severe frosts and cold in Florida there was an 

 abundance of northern insects, especially Orthoptera. 



