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ON THE IRREGULARITY IN THE APPEARANCE OF INSECTS, 

 AND ON THE UTILITY OF CALENDARS. 



BY SOLITARIUS. 



Experience soon teaches the young naturalist, that what in one 

 county, or even in one village, may be the usual time of an insect's 

 appearance, is at variance with the usual time in another. Though 

 we have much to learn before we can positively assert the causes 

 of these irregularities, yet when we consider the influence all created 

 things have upon one another, and how the life of one being depends 

 upon the existence of another, sufficient grounds present themselves 

 upon which we may at least attempt an explanation. In my pre- 

 sent paper I express my opinion that the time at which an insect 

 shall appear in its perfect state, depends primarily upon the adaptability 

 of the soil which is to nourish the plant upon which the young feeds. 

 We know that if the soil fails, the plant thrives not, and then the growth 

 and transformation of the caterpillar which feeds thereon is retarded by 

 the scantiness, or the unwholesomeness of the food, and consequently 

 the perfect insect makes a late appearance. But, on the contrary, 

 should the plant grow in a very favourable soil, it thrives well, and the 

 insect eggs, or other embryos, deposited in that soil, partaking of the 

 warmth, are hatched before their usual times, the caterpillar comes forth, 

 feeds upon the leaves, and soon assumes its perfect state. In both these 

 cases, we see that the soil is the main cause of both the late and early 

 appearance. It would, however, be hasty to conclude, that soil exerted 

 the only influence over the periodical appearance of insects ; for there 

 are certainly other causes, such as the prevalence of rain, frost, or sun- 

 shine. Besides the irregularity in the primary appearance of an insect 

 in its perfect state, there is also another circumstance to be observed, 

 which is, that when an insect makes its appearance, whether it be before 

 or after the usual time, it is rarely a general one all over the country. 

 In explanation of this let me suppose what is in point of fact the real 

 cause, the unequal distribution of temperature over the surface of the 

 country. The suburbs of London, for instance, during this month, may 

 be visited by rain or frost, which would retard the transformation of 

 embryos ; while, during the same time, the warm rays of the sun may 

 be throwing an exciting warmth over Bath, or any other place, and 

 accelerate their evolution. There being so many causes instrumental 

 in producing these anomalies, it renders it exceedingly difficult to form 

 a calendar of insects free from inaccuracies, though it may, in most 



