THE PARENTAL FORESIGHT OF INSECTS. 695 



having discovered a caterpillar or grub which her instinct informs her 

 has not been previously attacked, at once proceeds to thrust her ovi- 

 positor into the writhing body of her victim, depositing one or more 

 eggs, according to the size of the living food-supply. When hatched, 

 the larvae devour and live upon their fostei'-parent, avoiding in a mar- 

 velous way the vital parts of their victim, whose life is most accurately 

 timed to last until its young tormentors are full grown, and not be- 

 yond. At one time, we were led to believe in occasional instances of 

 the instinct of female ichneumons being at fault, by observing them 

 apparently ovipositing upon the dry shells of pupae from which the 

 butterflies had escaped. This, however, we subsequently found to be 

 an erroneous idea, the fact of the matter being that the caterpillar upon 

 which the parent ichneumon had laid her fatal egg had had time, be- 

 fore the full development of the young ichneumon grub, to turn to the 

 pupal stage. What, then, we saw was the young ichneumon-fly just 

 emerged from the dry pupal case, the contents of which it had first 

 devoured in its own larval stage, then, itself turning to a pupa, it had 

 lain, thus doubly incased, until, having broken forth a perfect fly, it 

 rested upon its late prison, awaiting suflicient strength to come to its 

 wings. What a wooden horse of Troy such a chrysalis would prove, 

 if introduced into the breeding establishment of a collector ! 



Other members of the ichneumon tribe do not actually insert their 

 •eggs into the destined food-supply of their young ; but, as it were, 

 going deeper into calculation of future events, content themselves 

 with laying them in close proximity to the eggs of some member of 

 the tribe upon which it is their mission to prey. 



There is an old saying : 



" Big fleas have little fleas 



Upon their backs to bite 'em ; 

 Little fleas have smaller fleas. 

 So on ad infiniUim " — 



which is very true, inasmuch as from the gi-eat humble-bee down to 

 the tiniest corn-thrips — a mere speck of dust to the naked eye — all in- 

 sects have their parasites, and generally their own special species of 

 ichneumon, to prevent their over-increase and to preserve the due bal- 

 ance of nature. There is a species of longicorn beetle, found in Penn- 

 sylvania, which feeds upon the tender bark of young hickory- shoots. 

 When laying-time arrives, the female, having deposited her eggs in 

 cavities perforated in the bark, carefully cuts a groove, about one- 

 tenth of an inch wide and deep, round the shoot just below where her 

 treasures lie. The object, or rather we suppose we ought to say the 

 •consequence, of this act is the withering and decay of the shoot, a 

 provision for the sustenance of her young, which, when in their larval 

 ^tate, live upon dead wood ! This remarkable insect is called the 

 hickory-girder from the above-mentioned habit, which, we think, is one 



