62 OF THE LARVA STATE. 



black colour, except the legs, which are yellow. By 

 breeding these flies in a state of confinement, and 

 introducing to them some Cabbage Caterpillars, 

 their proceedings in depositing their eggs may be 

 observed. We have more than once se on one of 

 these little flies select a Caterpillar, and perch upon 

 its back, holding her ovipositor ready brandished to 

 plunge between the rings, which she seems to prefer. 

 When she has thus begun laying her eggs, she does 

 not readily take alarm ; but, as Reaumur justly 

 remarks, will permit an observer to approach her 

 with a magnifying glass of a very short focus. 

 Having deposited one egg, she withdraws her ovi- 

 positor, and again plunges it, with another egg, into 

 a different part of the body of the caterpillar, till 

 she has laid in all about thirty eggs. It is not a 

 little remarkable, that the poor caterpillar, whose 

 body is thus pierced with so many wounds, seems to 

 bear it very patiently, and does not turn upon the 

 fly, as he would be certain to do upon another 

 caterpillar, should it venture to pinch him, a cir- 

 cumstance by no means unusual. Sometimes, indeed, 

 he gives a slight jerk ; but the fly does not appear 

 to be at all incommoded by the intimation that her 

 presence is disagreeable. 



" The eggs, it may be remarked, are thrust suffi- 

 ciently deep to prevent their being thrown off when 

 the caterpillar changes its skin; and being in due 

 time hatched, the grubs feed in concert on the living 

 body of the caterpillar. The most wonderful cir- 

 cumstance, indeed, of the whole phenomenon, is the 

 instinct with which the grubs are evidently guided to 



