INSECTS AND TEMPERATURE. 139 



circumstances favourable to them. Seasonable 

 weather is always favourable to insect life.* A mild 

 winter will tend to destroy the ensuing season's 

 general supply, by causing premature activity, fol- 

 lowed often by premature death, or at best by a 

 relapse into a state of torpor. These changes in- 

 variably prove prejudicial to the existence of insects. 

 Steady and severe cold, when seasonable, upon the 

 other hand, is not only favourable to insect life, by 

 causing a continued state of torpor, from which they 

 emerge in due season, but also by indirectly preserv- 

 ing them from the attacks of their numerous enemies. 

 It sometimes happens that, from a variety of causes, 

 running water is of a higher temperature than the 

 atmosphere, in dry frosty weather ; and as the aquatic 

 insect, prior to leaving its native element, is wholly 

 influenced by it, an uprising of them when the air 

 is too cold for them to live in it, is not by any 

 means an infrequent occurrence. We have observed 

 them rise to live but a few hours, and sometimes 

 only minutes, in the event of there being no sun 

 temporarily to counteract the effects of the keen air. 



* We remember ourselves witnessing, one very hot summer, which 

 had succeeded a hard winter, some forty years ago, a rising of iron 

 blues upon the Dovedale length of the Dove, that completely enveloped 

 the summits of the surrounding rocks, which appeared to be clouded 

 by a thick blue mist. There are instances on record of church spires 

 being taken to be on fire from a similar phenomenon. 



