of the Oil Beetle, Meloe, and of the Strepsiptera. 'Mb 



it. The mass was brought into view precisely in the middle line, between the 

 caudal setse, at the instant when the larva was in the act of carrying its poste- 

 rior segments forward, so that the fact could hardly be mistaken. This appears 

 to be sufficient evidence of the existence of an anal outlet to the digestive 

 canal. That this may become closed at a subsequent period, when the Sty- 

 lops larva has penetrated into the interior of the body of its victim, is highly 

 probable, although it is most certainly permeable in the male imago, which 

 Mr. Pickering saw void a whitish fluid immediately after it came forth, analo- 

 gous probably to that passed at a similar period after evolution from the pupa 

 state by the Lepidoptera and other insects. The Stylops larva, near the end of 

 its period of nutrition, in its apodal state, has been found by Peck, Jurine and 

 Dufour completely inclosed in the body of the hymenopterous insect, feeding, 

 according toDufour's observations, on the adipose tissue only, and not on the 



vital structures. 



Respiratory Organs of Stylops. 



The complete occlusion of Stylops within the body of another insect ren- 

 ders the consideration of the manner in which the function of respiration is 

 performed, or the aeration of the fluids in the parasite is effected, — a condition 

 essential to life, — a matter of interest equal with that of the closure of the 

 outlet to the digestive canal. It can hardly be imagined that an insect, the 

 male sex of which in its perfect state is one of the most active and fully deve- 

 loped of the winged tribes, does not possess, in its larva state, organs in some 

 form or other fitted for an extensive aeration of its fluids. The existence of 

 a large spiracle in the thorax of the female Stylops communicating with large 

 tracheae extensively ramifying through its tissues, shows that while it is pass- 

 ing the greater portion of its existence surrounded by delicate organs in the 

 body of another animal, and as it were bathed in its fluids, it yet maintains 

 for itself a free and perfectly independent respiratory function of its own. 



In all the larvae I have examined there have appeared to be eight pairs of 

 bag-shaped dark-looking bodies within the abdomen, one pair at the sides of 

 each segment, from {h&Jifth, or second abdominal segment to the eleventh 

 inclusive, situated in the exact place of the respiratory organs of other insects. 

 From their darkened appearance, and from their resemblance to branchial 

 sacs, these may perhaps be regarded, at this period of the larva's existence, as 



