74 THE REPORT OF THE No. 19 



Curiously enough, despite the attack of these mites, one of my assistants, Mr. Newell, took a 

 quantity of this mass of powdered meal and mites and with this was enabled to get a fine culture 

 in a bottle of the sterilized meal and broth dough. 



The mite attacks not only cheese but sugar, tl mr, cured hams, wool, seeds and many other 

 articles of food and commerce. Evidently it is in this case the dough that attracts them, but as 

 against them this species of entomogenous fungi is clearly harmless. 



THE HIBERNATION OF INSECTS. 



By Prof. VV. Lochhead, Ontario Agricultural College. 



A very puzzling question, yet a very important one, is frequently asked : " Why do some 

 insects pass the winter as aduhs ; some as pupae ; some as larvae ; and others in the egg 

 stage ? " 



To answer this question the entire history of the development of insects would require to 

 be known, for there seems to be but little doubt that the particular hibernation form is the 

 visible expression of the influence of many factors, such as change of environment, nature and 

 abundance of food, and change of habit. The question of hibernation is clearly closely 

 associated with that of metamorphosis, and any intelligent discussion of hibernation must 

 necessarily deal with the causes of metamorphosis. When this connection is realized, it is 

 plain that in dealing with hibernation forms of insects we are dealing with one of the most 

 difficult problems in biology. No attempt will be made here to solve the difficulty, but, perhaps, 

 the presentation of a few facts regarding hibernation forms may be useful and interesting. 



The members of the order Orthoptera, almost without exception, hibernate in the egg stage; 

 the Hemiptera mainly in the egg, or adult condition ; the Neuroptera as larvae ; the Lepidoptera 

 in the egg, larval, pupal, or adult condition ; the Coleoptera as pupae or adults ; the Hymenoptem 

 as larvae or pupae ; the Diptera as larvae, pupae, or adults. 



According to the foregoing, it would appear that the insects that pass through an incomplete 

 metamorphosis have but one, or at most two, forms of hibernation, while the insects which 

 pass through a complete metamorphosis have several forms of hibernation. 



When we remember that the modifications in the stages of metamorphosis are modifications 

 in the form and functions of organs in adaptation to a changed environment, it becomes evident 

 that the insect may winter over in any one of the four stages. That stage will be chosen which 

 will suff'er least by the change of environment. For example, in those forms whose larval 

 existence is spent in semi-liquid decomposing matter, it would be practically disastrous for them 

 to remain as larvae, when intense cold sets in and changes the condition of the medium. They 

 are more likely to survive as pupae, or adults, in a dry medium. 



With reference to metamorphosis, insects are divided into the Hemimetahola, or those with 

 an incomplete metamorphosis, and the Holometabola, or those with a complete metamorphosis. 

 In the former there is a gradual change from the larva to the perfect insect, while in the latter 

 the insects pass through a resting pupal stage. 



VS'ith regard to the stages of development, some of them show better adaptation t() 

 hibernation than others, although it is impossible at present to explain why some buttertlies 

 winter over in the adult state and others in the chrysalis ; or why some flies winter over in the 

 larval state, some in the pupal, and others in the adult. 



Brief notes of the stages will be given here beginning with the Egg, dwelling chiefly on 

 characters which enable the insect to hibernate. 



The Eggs. Eggs of insects are protected by two coats or membranes, an inner vitelline 

 membrane, and an outer chorion, composed of two layers. When eggs are laid in situations 

 exposed to the weather and cold, the shell, or chorion, is very solid, and sometimes strengthened 



