106 MEANS CONTRIVED BY NATURE TO LIMIT 



injury to the fruit-trees, dying by thousands, as if of a dropsy. The cater- 

 pillars swelled, became weak, and died. If they did attain the pupa state, 

 they suffered from the same evil, and the perfect insect was very rarely 

 developed, on which account the gardens in the following years were entirely 

 spared. 



337. Late frosts are also very beneficial, as they entirely destroy many 

 insects in their larva state. Kollar had an opportunity early in the summer 

 of 1833 of observing great devastations on the fir-trees in the neighbourhood 

 of Vienna, by a species of saw-fly ( Tenthredo rufa King). The larva of 

 this insect had attacked certain parts of a young forest of Scotch pine, and 

 the question was how their ravages were to be prevented from increasing- 

 next year. Fortunately, in the month of May, a moderate frost set in, and 

 thousands, of these larvae were seen hanging to the twigs, as if scorched. In 

 this manner their increase was limited for the future. 



338. A multitude of insects are also destroyed by inundations, particu- 

 larly such as undergo their transformations in the earth, or live upon it in 

 all their stages, more especially if the inundation happens when they are 

 near their final transformation. In meadows the different species of May- 

 bugs ( Jfelolonthidae) suffer by this means ; in kitchen gardens, the mole- 

 cricket; in orchards, the pupa of the small winter-moth (Geometra bru- 

 mata), when the water overflows the gardens late in the autumn, at the 

 time when the moth is usually developed from the pupa lying in the earth. 

 Besides the means of preserving an equilibrium by storms, and the effects 

 of the elements, nature employs a multitude of others, although not so 

 speedy and efficient, to the same end. 



339. To these belong the enemies of the destructive insects, which we meet 

 with in all classes of the animal kingdom. Among the mammiferous ani- 

 mals the bats hold a conspicuous place for their destruction of insects. We 

 only see them flying about in the twilight, precisely at the time when many 

 moths leave their hiding-places and hover round the flowers. As they live 

 almost entirely on insects, they no doubt devour great numbers of the 

 hurtful sorts ; and perhaps it is to be ascribed to this circumstance that 

 fruit-trees standing near houses, churches, barns, &c., suffer less from insects 

 than isolated trees. Bats do not confine themselves to moths, but eat 

 the beetles which fly about in the evening ; and, among others, some of the 

 weevils injurious to the flowers and buds of fruit-trees, as the Curculio 

 (Anthonomus) pomorum, and pyri. These creatures, as they do no injury, 

 should therefore be carefully preserved. 



340. To the insectivorous mammalia also belong various sorts of mice, the 

 mole, badger, hedgehog, squirrel, fox, and wild swine. Whether the 

 benefits derived from them hi this way counterbalance the mischief which 

 many of these creatures cause, it is difficult to determine. At all events, 

 the squirrel and the hedgehog deserve to be spared. 



341. Birds contribute much more than the mammiferous animals to the 

 destruction of injurious insects. Many caterpillars know instinctively how to 

 conceal themselves from the birds which prey on them ; in many their 

 covering of stiff hair acts as a protection against their enemies ; others 

 remain all day between rolled-up or flatly-united leaves, and only go out to 

 feed at night ; others find sufficient protection in the buds, into which they 

 soon penetrate. Gregarious caterpillars live while they are changing their 

 skin, and when they are going into the pupa state, in webs, in which they 



