INSECTS, OR DESTROYING THEM. 67 



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 sub- 

 stance has been dissolved, such as quicklime or potass ; or a bitter 

 or poisonous infusion may be made, such as quassia or 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 larvae of mining insects, in which the larva is 

 concealed within the epidermis of the leaf, there is no way of destroy- 

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

 the finger and thumb. 



Collecting the Pupcs 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 butterflies. 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 pass through its pupa state ; and 

 in some cases it may be destroyed by watering the soil with boiling 

 water, or by deep trenching ; the surface soil, containing 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 circumstances 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 butter- 

 fly. 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 

 gardener, 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 pre- 

 pared 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, insects already known. 



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