104 HYMENOPTERA CHAP. 



immediately to the second spot, where it had last left the spider, 

 thus showing that it possessed an accurate memory for locality ; 

 the wasp was very much surprised at the absence of the valued 

 prize and persisted in seeking it in the immediate vicinity with- 

 out once returning to the place where it had been first located. 

 Fabre repeated this manoeuvre five times, and the Pompilus 

 invariably returned at once to the spot where it had last left its 

 prey. The acute memory for localities displayed by this Insect 

 seems to be more or less general throughout the Aculeate 

 Hymenoptera, and is of very great importance to them. The 

 power of finding the object appears to depend on sight, for when 

 Fabre, after removing the spider to a fresh spot, made a slight 

 depression in the ground, placed the spider in it and covered it 

 over with a leaf, the wasp did not find it. At the same time, the 

 Insect's sight must be a very different sense from our own, for the 

 wasp, when seeking its lost booty, frequently passed within a couple 

 of inches of it without perceiving it, though it was not concealed. 



Belt gives an example of the habits of the Mexican Pompilus 

 polistoides. He noticed it, when hunting for spiders, make a dart 

 at a web in the centre of which a spider was stationed ; by this 

 movement the creature was frightened and fell to the ground, 

 where it was seized by the wasp and stung. The Pompilus then 

 dragged its prisoner up a tree and afterwards flew off with it, 

 the burden being probably too heavy for conveyance to the nest 

 without the vantage of an elevation to start from. 



Several modifications adopted by Pompilidae in their mode of 

 stinging their spider-victims have been recorded by Ferton ; these 

 we cannot allude to in detail, but will nevertheless mention that 

 one species stings the body of its spider-prey at random, and 

 that in other cases it would appear that the paralysis of the 

 spider is evanescent. In short, there are various degrees of 

 perfection in the details of the art of stinging. 



The most remarkable of the forms of Pompilidae are the 

 numerous species of Pepsis, a genus peculiar to America, whence 

 upwards of 200 species are already known. 1 Some of them 

 attain a length of two inches or more, and are able to conquer 

 the largest spiders ; even the formidable Mygale avicularis 

 succumbs to their agility and skill. Some of these Pepsis have 

 beautifully coloured wings ; according to Cameron, this may be 



1 Monograph by Lucas, Berlin ent. Zeitsclir. xxxix. 1894. 



