58 MEANS CONTRIVED BY NATURE TO LIMIT 



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, 

 Klug). The larvae 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 time. 



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 (Melolonthidae) suffer by this means ; in kitchen 

 gardens, the mole- cricket; in orchards, the pupa of the small winter-moth 

 (Geometra brumata), 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. 



To these belong the enemies of the destructive insects, which we 

 meet with in all classes of the animal kingdom. Among the mammi- 

 ferous animals 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 inju- 

 rious to the flowers and buds of fruit-trees, as the Curculio (Antho- 

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

 should therefore be carefully preserved. 



To the insectivorous mammalia also belong various sorts of mice, 

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



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 protec- 

 tion in the buds, into which they soon penetrate. Gregarious cater- 

 pillars live while they are changing their skin, and when they are 

 going into the pupa state, in webs, in which they are inaccessible to 

 birds. Others live under the bark of trees, and even deep in the 

 wood. Notwithstanding these and other obstacles, a great number 

 are yearly devoured by the birds, particularly during the breeding 



