292 AFFECTION OF INSECTS FOR THEIR YOUNG. 



returned and took it up again. But for the ensuing twenty 

 or twenty-five feet it never stopped, but proceeded in a direct 

 line for its burrow with the utmost speed. When opposite 

 the hole, which was in a sand bank by the way side, it made 

 a sharp turn, as evidently aware of being in the neighbourhood 

 of its abode, but when advanced a little further laid down its 

 burthen and went to reconnoitre. At first it climbed up the 

 bank, but, as if discovering that this was not the direction, 

 soon returned, and after another survey perceiving the hole, 

 took up the spider and dragged it in after it. 



In the two instances above given, one dead caterpillar or 

 spider only was deposited in each hole. But an insect 

 described by Reaumur under the name of the mason-wasp 

 {Epipone spinipes\ very common in some parts of England, 

 after having excavated a burrow, with an ingenuity to which 

 on a future occasion I shall draw your attention, places along 

 with its egg as food for the future young, about twelve little 

 green grubs without feet, which it has carefully selected full 

 grown and conveyed without injuring them. You will inquire. 

 Why this difierence of procedure ? With regard to the choice 

 of a number of small grubs rather than of one large cater- 

 pillar, what I have said in a former letter on the subject of 

 different species of this tribe being appointed to prey upon 

 and thus keep within due limits the larvas of different kinds of 

 insects, will be a sufficient answer. But one circumstance 

 creditable to the talents of the mason-wasp as a skilful pur- 

 veyor should not be omitted, namely, that the number of 

 grubs laid up is not always the same, but is exactly propor- 

 tioned to their size, eleven or twelve being stored when they 

 are small, but only eight or nine when larger. With respect 

 however to the caution of the wasp in selecting full-grown 

 grubs and conveying them uninjured to her hole, a satisfactory 

 explanation may be given. If those that are but partly grown 

 were chosen, they would die in a short time for want of food, 

 and putrefying would destroy the enclosed egg, or the young 

 one which springs from it. But when larvae of any kind have 

 attained their full size, and are about to pass into the pupa 

 state, they can exist for a long period without any further 

 supply. By selecting these, therefore, and placing them un- 



