AUSTRALIAN HTMENOPTEEA ACtTLEATA. 319 



produces quite a different sound. It has now an exceedingly high 

 pitch ; and from my observations of the wasp at work, I believe it is 

 the result of the vertical motion of the abdomen from the pedicle. 



a-e. Outlines, nests of PelojocBUS latus, nat. size. 



The work which the wasp undertakes in building her nest may 

 be judged from the number of times she takes to go to and from 

 the wet earth. On Oct. 13, 1883, I timed a wasp at her work. 

 In the course of 22 minutes she fetched mud at a distance of 5 

 yards ; 13 times at the following intervals — at 14|-, 12^, 10|, 91, 

 7g, 6|, 4, 1| minutes to 3 o'clock in the afternoon ; then at 3 p.m., 

 1, 3|, 5|, 7| minutes past 3, when I ceased my observations. 



When one cell is completed the wasp goes in search of spiders, 

 of which she generally collects from 15 to 22 specimens of three 

 moderate-sized species. It is very seldom that any other species 

 of spiders are collected. She takes them one by one and packs 

 them half dead in the cell, being very particular as to the 

 way in which they fit in. "When the cell is full she deposits 

 an egg, somewhat smaller than that of JEumenes Latreillii, and 

 the egg is laid on one of the benumbed spiders. She then 

 closes the top of the cell with mud and commences a fresh 

 cell at its side. She builds the cells in a row side by side, but 

 the row is seldom straight, and she lacks that exactitude and 

 neatness which characterizes the work of Eumenes. Sometimes, 

 if disturbed, she will close a cell without putting in any spiders 

 at all, and at other times she will only half fill the cell. The cell- 

 wall attains a thickness of § inch. The wasp constructs from 10 

 to 20 of these cells in two rows one above the other, fills the 

 interstices between the cells with mud, and smears the whole over 

 with mud likewise, until it resembles along lump of clay, and at 

 this stage the nest is undistinguishable in outward appearance 

 from that of the Uumenes. But if allowed to continue her work 



