Hugh Scott 105 



against its puparium and killed by the invading Necrobia-larva. Gallois, 

 however, says nothing about the Necrobia-laiva actually eating the 

 nymph of the fly. Taschenberg(25) apparently made no observation of 

 the Necrobia eating into intact puparia. 



On 11. iv. 1917 I placed four partly grown iVecro6j'a-larvae in a 

 vessel with a number of sound puparia of Musca domestica and no other 

 food; I failed to examine them again till 2. v. 1917, by which time two 

 of the Necrobia had pupated and the other two had disappeared, but 

 five puparia had been broken into, one in two places, and cleaned out. 



In the two following cases the iVecro6m- larva was watched in the 

 act of boring its way into an intact puparium of Musca domestica. My 

 attention was drawn to one of them by Mr LI. Lloyd, who discovered 

 the larva in the act. Li one of these cases the contained nymph may 

 have been dead, though the puparium was intact. The first of these 

 two Necrobia-lavvsie looked about two-thirds grown, and was found — 

 not in one of the small vessels, but in a big vessel containing a mass of 

 fly-maggots, food, and debris — entering the puparium (which was a 

 small one) through a small hole on the left side of the 2nd and 3rd 

 segments, dorso-lateral in position. Being disturbed, the larva backed 

 out of the hole, but soon started in again, and got its whole body inside, 

 the terminal segment and brown chitinous hooks disappearing after a 

 few moments. During the next two hours it could be seen through the 

 hole, moving about inside. For the next 3 days it remained in the 

 puparium, the hole being blocked by a projecting mass of pellets of moist 

 brown frass. When next looked at, 6 days later, the larva had come 

 out again, having about doubled the size of the hole by eating away 

 the substance of the puparium irregularly towards the anterior end. 

 The puparium was absolutely cleaned out, no trace of nymphal sub- 

 stance being left in it. The Necrobia-lsLrva, was found dead a fortnight 

 later, having refused several other kinds of food. The second larva was 

 found (21. ii. 1917) entering a larger puparium by a hole much further 

 back, in the 4th and 5th segments. At intervals up to 2. iii it could 

 be seen moving about inside, the hole not being blocked; on 15. iii the 

 hole was found blocked, and by 17. iii it was covered with the screen 

 of hardened white secretion made by the Necrobia before pupation. 



(iii) Eating dead adult flies. Several houseflies emerged from 

 puparia in the small vessels with the Necrobia-\a,Tva,e, and died in the 

 vessels. Their remains were found with the soft parts of thorax and 

 abdomen eaten out, and heads, wings and legs scattered about. [Adult 

 Necrobia also ate dead flies; see below.] 



Ann. BioL vi 8 



