THE MUD-DAUBERS. 179 



six years, or, to be more exact, five hundred and forty-six nests 

 out of five hundred and seventy-three, had their openings at the 

 top, the longitudinal axis being nearly vertical, while twenty- 

 seven were placed horizontally, with the opening at the side, 

 (PL X., figs. 2-3.) Eabre found chat in France, Pelopaeiis 

 always gave the cell a horizontal or slightly oblique direction 

 with the opening out or a little up. With our wasps the vari- 

 ation in the position of the cells was an individual affair, sinc3 

 one would sometimes change the direction of the cells she was 

 making. One fickle-minded worker built two with their open- 

 ings directly up, and then placed a third cell at right angles to 

 these with the opening out. Another made sixteen vertical 

 cells and then, changing her plan, placed two horizontally. 

 "We found another group of six, of which four opened up and 

 two out, and still another with five up and four out. So far as 

 we could see the one direction possessed no advantage over the 

 other. Maindron, in describing the habits of Pelopaetis in the 

 Indian Archipelago, says that what strikes him most in the 

 aispect of their nests is their great variability. He has nevsr 

 found two alike in exterior form, in volume, or in the number 

 of cells, and these also vary greatly, although they are almost 

 always oblong.* 



So soon as the cell is done, even if it be late in the afternoon, 

 the wasp begins to lay in the food supply for her offspring. In 

 this she differs from most of her relatives, as few of them wiU 

 work after four o'clock. In favorable weather the blue wasp 

 often builds and stores a nest in a single day. The prey that 

 she seeks is spiders, and this- seems to be true of Pelopaeus all 

 over the world. They take spiders of many different kinds but 

 always spiders. If a wasp begins to put a coramon species into 

 lier nest she is very likely to continue with it until the cell is 

 full, but she exercises a wise eclecticism in her choice and saves 

 herself all the trouble that she can. In spring and through 

 mid-summer our wasps most frequently take Epeira strix, vul- 



*Ann. Soc. Entom. de France, Tome VIII., p. 338. 



