114 AMPHIBIOUS ANIMALS CONSIDERED. 



time, the fruit not falling until the grub has arrived at its full size. The 

 larvse of some kinds of saw-flies envelop themselves in a kind of web in 

 the day-time, and only go abroad to feed during the night. Webs of this 

 sort may be seen in great numbers, in the early part of summer, on thorn 

 hedges, fruit-trees, spindle-trees, and a great many others ; and they might 

 readily be collected by children or infirm persons, and thus myriads of 

 insects destroyed. The larva may be destroyed, both in its infant and adult 

 state, by dashing against it water in which some caustic substance has been 

 dissolved, such as quicklime or potass ; or a bitter or poisonous infusion may 

 be made, such as tobacco-water. While the larvae are not numerous, or the 

 plants infested by them are tender and highly valued, they ought to be collected 

 by hand ; and in the case of the larvse of mining insects, in which the larva 

 is concealed within the epidermis of the leaf, there is no way of destroying 

 them but by gathering the leaves, or crushing the insects between the finger 

 and thumb. 



SGI. Collecting the Pupa or Chrysalids. Insects may be destroyed in the 

 pupa state by collecting their chrysalids or cocoons, when these are placed 

 above ground, as is most commonly the case with those of moths and butter- 

 flies. These are commonly deposited in crevices in the old bark of trees, or 

 in sheltered parts of walls or buildings ; rarely on young shoots or in the 

 tender parts of plants, because, when the perfect insect comes forth, it no 

 longer requires such food. Often the larva descends into the soil, there to 

 undergo its pupa state ; and in some cases it may be destroyed by water- 

 ing the soil with boiling water, or by deep trenching ; the surface soil, con- 

 taining the insects, being placed in the bottom of the trench. As the eggs 

 and chrysalids require the presence of air for their vivification and maturity 

 no less than the seeds of vegetables, they are consequently, when deposited 

 in the soil, always placed near the surface ; and hence they may be destroyed 

 either by heaping earth on the surface, or by trenching or digging down the 

 surface soil, so that the eggs or pupae may be covered at least to the depth 

 of six inches. How long vitality will be retained under such circum- 

 stances is uncertain. In destroying the cocoons of insects, care should be 

 taken not to destroy those of the insect's enemies, such as the cocoons of the 

 spider, or those of the ichneumon flies. These are sometimes deposited in 

 heaps on the bark of trees, and are individually not larger than the egg of a 

 butterfly. The gardener ought to be able to recognise them, because they 

 are his best friends. 



This general outline will be sufficient to show the necessity of every gar- 

 dener, who would be a master of his profession, studying the natural history 

 of insects, and more especially of those which are known to be injurious or 

 useful to him, whether in the open garden or in plant-structures. It is only 

 by such a study that he can be prepared to encounter an insect which he 

 has never heard of before, and that he will be able to devise new modes of 

 counteracting the progress of, or destroying, already known insects. For 

 this purpose we recommend to his study the work of Kollar already men- 

 tioned, and next Mr. Westwood's Introduction to the modern Classification 

 of Insects. 



SECT. IV. Amphibious Animals, considered with reference to Horticulture. 



362. The frog, TJana temporaria L., and the toad, Bufo vulgaris Fleni,, 



are found useful in gardens, because they live upon worms, snails, slugs, and 



