THE EUMENIDAE 351 



fashion they were neatly suspended from the walls by a 

 short silken thread. The egg was 5 mm. long, and the 

 thread about one-half of that length. The two bee cells 

 used for this nest had originally been built at right angles to 

 each other, and had been utilized by M. quadndens without 

 alteration. One of the eggs, deposited between 10 a. m. 

 and 4 p. m. on July 16, was placed in a vial together with its 

 portion of the caterpillars, eighteen in number. The larva 

 devoured all of them, pupated, and on August 19 emerged 

 as an adult male, after a period of one month and three 

 days for the three stages. It left no evidence of having spun 

 a cocoon. This would indicate two generations per year. 



In another cell which was opened, the empty egg-shell 

 was still hanging from the wall, thus showing that the larva 

 had crawled out of the egg-shell, instead of behaving as 

 some Hymenoptera do, where the egg merely assumes form 

 and eventually imbibes at one end. Most of the caterpillars, 

 when the larva is done with them, are merely sucked dry. 

 but a few bear marks where the chitin has been eaten. 

 Obviously, where so enormous an amount of food is sup- 

 plied, there is no necessity for the larva to consume the un- 

 desirable parts of the carcass. 



Once, when digging up some burrows in the clay bank, 

 we accidentally broke into the nest of a M. quadridens, 

 which was in course of construction. The wasp returned and 

 spent a long time evidently either looking for a lost hole or 

 prospecting for one, poking her head into many holes, 

 deep and shallow. The next morning at 10 o'clock, she was 

 busy enlarging a shallow opening by carrying out wet 

 pellets of dirt. Her trip for each mouthful of water took 

 four minutes. While the hole was yet shallow, she carried 

 out the pellets by flying backwards ; later she usually walked 

 to the orifice backwards, released the pellet at the brink 

 where it would roll down the steep surface of the bank, and 



