346 Mr. Newport on the Natural History 



imperfect respiratory organs, of the nature of branchiae. A branchial form of 

 respiratory organs we know exists in the aquatic larvae of insects which, in 

 their perfect state, respire atmospheric air, and it is not improbable that alike 

 condition of the respiratory organs exists in the early states of this parasite. 

 The larva of Ichneumon atropos, however, in which I have found that there 

 certainly is no outlet to the alimentary canal, and which, as before stated, 

 subsists on the adipose tissue and fluids of the caterpillar, has true, but ex- 

 tremely minute spiracles and air-vessels, and although completely inclosed in 

 the body of the caterpillar, seems to respire the air directly, perhaps from the 

 injured air-vessels of its victim. 



Development of the Larva of Stylops. 



When the young Stylops has penetrated the body of the bee-larva, shut up 

 in its cell in the earth in the spring, it grows as rapidly as the larva itself is 

 nourished. It certainly changes its skin once, and perhaps oftener, like other 

 insects. Its need for organs of locomotion, and for the perception of surround- 

 ing objects, is then reduced to a minimum. Accordingly, as I shall presently 

 show takes place also in Meloe, inclosed in the cell of Anthophora, the legs 

 with which the young Stylops was provided when it issued from the body of 

 its parent become atrophied, and their further development is so completely 

 arrested in every part, owing, perhaps, to the excess of growth which is taking 

 place in its other structures, that they entirely disappear, being first reduced 

 to their merest possible rudiments, pedal papillae, which are more and more 

 reduced in size as the growth of the body proceeds. On the other hand the 

 body of the Stylops becomes so enlarged by the nourishment ingorged from 

 the substance of the body of the bee-larva, that its entire form and propor- 

 tions are completely changed. 



During the period of its growth, the parasite, as found by Dr. Peck * in 

 Xenos, lies with its head in the direction of that of the insect preyed upon, — 

 that probably in vv-hich it entered the body. But when it has arrived at its 

 full growth, and is about to change to a nymph, its position in the body is 

 reversed, and adapted to its future exit backwards between the rings of the 

 abdomen of the hymenopterous insect. Its change to a nymph takes place in 



* Trans. Linn. Soc. vol. xi. 



