and Relations of the Wasp and Rhipiphorus. 353 



and to spin it equally well with its tail as its head. I do not 

 say that it does not ; but it seems a very unusual aggregation 

 of gifts, an accumidatio munerutn for which there is no pre- 

 cedent. Nature never provides for unnatural or exceptional 

 events, but leaves the unhappy victim of them to meet its fate 

 and die. 



The explanation which has occun-ed to me is this — a little 

 far-fetched, perhaps ; but the difficulty seems to warrant a 

 stretch. There are two difficulties, the supply of the material 

 and the spinning. As to the first, it must be remembered that 

 the position of the cell is mouth downwards ; so that if the 

 fluid silk or glue was ejected in quantity from the mouth of 

 the larva, it would naturally flow down its body or along the 

 walls to the mouth of the cell. I suppose that the grub at 

 that stage of its existence is constantly expectorating some of 

 this glue (if we touch its head at that period, it may be seen 

 to eject from its mouth a bell of clear liquid like water, which 

 I have no doubt is liquid silk), and that the slimy-looking 

 stuff on the walls of the cell is part of it which has adhered to 

 them. When the grub is ready to pass into the pupa-state, it 

 spins it into the lid ; and its weight, elasticity, and adhesive 

 qualities make it take the cup-shaped form the lid bears. If we 

 examine one half finished, we see the threads crossing the out- 

 side rough and somewhatwoolly; but I suppose aquantity of glue 

 poured out on it from within, after it has reached this stage, 

 penetrates the interstices and gives the outside the glossy look 

 which the finished lid bears. Suppose, then, the larva reversed, 

 no change will take place so far as regards the glue on the walls ; 

 it flows down them and coats them as before ; but when the 

 larva begins to spin, the head being now uppermost (the mouth 

 of the cell being downmost), the glue will fall back and flow 

 past the grub to the moutli of the cell. This would explain 

 why there is no lid in the middle between the two pupse ; 

 the movement of the other larva would be sufficient to pre- 

 vent its settling, and the matter would then by gravitation 

 find its way downwards. If the larva then is restless and 

 moves its tail (which, although used as a sucker, it can de- 

 tach and move as it likes) from side to side, it would imitate 

 the motion of spinning and prepare a sieve of sufficient fine- 

 ness to retain any more liquid that flows down, and so com- 

 plete the lid. The only diflbrence from the usual process 

 would then be, that, instead of the material being supplied 

 from the pendent mouth, it streams backwards down its 

 body. That the larva has enough of this glue streaming 

 from its mouth to cover the whole body will be apparent to 



