A HISTORY OF DEVONSHIRE 



The eggs of the Ichneumonidae vary greatly in shape, size, and colour ; the great majority, 

 about 95 per cent., cannot be seen, from their being deposited beneath the skin ; an indication 

 when recently pierced is often observed by a black dot on the caterpillar : should it change its skin 

 the mark is removed. Eggs laid on the surface of the caterpillar before the last moult are removed 

 with the change of skin, and leave no ill effect. Those laid after the last moult are carried by the 

 larva into its resting place ; the larva is then consumed. Notwithstanding the aggressive nature 

 of the work allotted in nature to these parasites, it is worthy of remark that in their earlier stages 

 of existence they are exceedingly delicate and cannot stand the slightest injury ; an abrasion of the 

 surface of the skin sufficient to allow the least portion of the fluid to escape would prove fatal ; yet 

 these very larvae, 'having passed unhurt through this scarcely other than foetal condition, acquire a 

 perfection of organization, a degree of activity and power, and an acuteness of instinct fully equal, 

 or perhaps superior, to the organic and the functional endowments of other tribes of insects.' One 

 egg only of the larger species is usually deposited in each caterpillar. If, howrcver, two should be 

 laid either by the same parent, or by a separate female of the same or of an allied species, both eggs 

 may be hatched, but the weaker would fall a victim to the stronger, that is, supposing the food to be 

 only sufficient for one; but with the smaller parasites of the Braconidae group, i8o have been 

 known to emerge from one caterpillar, Arctia caia, Linn., whereas the same larva would only 

 sustain one of the larger species (Pimpla instigator, Fab.). The larvae of the Ichneumonidae without 

 exception are legless and entomophagous, and when they leave the egg are quite incapable of 

 locomotion. 



The eggs deposited in the body of the caterpillar soon mature ; the larvae finding plenty of 

 food do not move, but lie perfectly motionless, embedded in the fatty tissue between them and the 

 alimentary canal, always on the dorsal surface, and usually with their heads in the direction of the 

 head of the caterpillar, and are nourished entirely by suction. 



The general form of the body and the construction of the digestive organs at the earlier periods 

 of the growth, are almost, if not precisely, the same in most of these parasites. The special 

 development of each is regulated by the same laws ; they cast their skins at succeeding stages of 

 growth as certainly as do the larvae of butterflies and moths. 



The protection of the larva during its change to the pupa stage, and from that to the perfect 

 fly, is very variable. Many make cocoons after the manner of ordinary silkworms ; but in the 

 genus Ichneumon and many others, they do not make cocoons in any form, but remain in the 

 pupa-case of their host for final transformation to the perfect insect. 



In the genus Ophion and many others, the parasitic larvae construct cocoons for them- 

 selves. Ophion on or below the surface of the earth. The Limneria, however, remain on 

 the twig, leaf, or branch, on which the caterpillar was resting, the parasitic larva issuing 

 from its host on the underside ; the empty skin of the caterpillar is often found attached 

 to the cocoon {Limneria ruficincta, (jravenhorst). Others do not leave the body of their 

 victim, but make use of the skin of the caterpillar as an outer covering ; the commonest met with 

 is that of Limneria vulgaris, Tschek., a parasite on the Brimstone butterfly larva {Gonopteryx rhamni, 

 Linn.). One of the most wonderful forms of protection is that manifested by the larva of Limneria 

 Kriechhaumeri, Bridgman. It makes a very curious oval cocoon about the size of a large hempseed 

 on its leaving its host, the common quaker {Taeniocampa stabilis, Vieweg.). Directly after leaving, 

 the maggot-like form suspends itself by a silken thread, about two inches in length, previously 

 attached to the tree on which the caterpillar was feeding, and commences to make its future abode, 

 in which it has to pass the winter. The form is that of an oblong sphere 6 mm. by 4, chocolate 

 colour, with a whity-brown zone in the middle. It is after the cocoon is made that the wonder and 

 agility of the larva, within the cocoon, must be looked upon by all who have seen it with the greatest 

 astonishment. Shortly after the aSrial cocoon is finished it is blown down by the wind ; but sup- 

 posing there is no wind, or but little, not sufficiently strong to blow it down, it begins to bound 

 about with a view to breaking the suspending cord. When that is accomplished, and it feels itself 

 on the ground, the cocoon begins to jump about, making leaps 300 times its own length, until it 

 has jumped or bounded into a place whence it cannot extricate itself. It then commences to roll, 

 first on one side and then on the other, until it finds itself fixed, unable to move any way. It is 

 then satisfied, and no further attempt is made ; but remove it from the spot after some days, and it 

 will again go through the same performance, and repeat it, as often as it is removed, until it is 

 exhausted. The manner of jumping at least 300 times its own length, when confined within the 

 walls of its cocoon, is one of the greatest curiosities in nature ; yet it is done by the larva within the 

 cocoon bringing its head and tail together and suddenly straightening itself out, as would a piece of 

 steel, if the two ends were brought together and suddenly released. The maggot of the dipterous 

 fly often found in old cheese does the same, and it is generally known by the name of cheese- 

 hopper {Piophila casei, Linn.) from its hopping propensity ; but this larva has no impediment ; the 

 other is enclosed in its cocoon. 



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