340 NATURAL THEOLOGY. 



tails of various species of flies ; and with which 

 they pierce, in some cases, plants ; in others, 

 wood ; in others,^^ the skin and flesh of animals ; 

 in others, the coat of the chrysalis of insects of a 

 different species from their own ; and in others, 

 even lime, mortar, and stone /^ I need not add, 

 that having pierced the substance, they deposit 



are slothful, and very strong, and burrow in the grovuid by means 

 of their fore legs. 



A great analogical resemblance al^o exists between an insect 

 called the mole-cricket and. the mole, their habits also being 

 similar. 



82 Almost every caterpillar (perhaps, without exception) has its 

 peculiar parasites among the ichneumonidse, a difterent tribe of 

 insects : the same ichneumon almost invariably choosing the 

 same caterpillar to deposit its eggs upon or in ; and as the situa- 

 tions in which difterent caterpillars feed are very various, so is 

 the structure of their parasites. The ichneumons which infest 

 internal feeding caterpillars (i. c, such as feed in the trunk of a 

 tree, or the stein of a plant) are furnished with long ovipositors to 

 enable them to reach the caterpillar through some hole or chink 

 where they themselves cannot get. 



Even the ichneumons are not free from parasites. There are 

 instances where four or five different parasitical insects have been 

 found in the same chrysalis, (as that of the Trichiosoma leucorum, 

 a saw-fly,) each one feeding upon the other. Thus several larvce 

 of an ichneumon may be found feeding upon the inside of a chry^ 

 salis ; and when these larvte turn into pupa? or chrysalides, some 

 of the chalcidida?, a different tribe of flics, will feed upon them, 

 and even some of the last may in their turn be eaten up. 



*^ There is not any accredited instance of any insects perfora- 

 ting so hard a substance as stone, with the * awl or borer' fixed at 

 the tail. This instrument, technically called ovipositor, is exces* 

 sively variable in its structure, being scarcely alike in any two 

 species : the description given will answer for that of the saw-fly, 

 {Ter.tredo.) 



