386 Trans. Acad. Sci. of St. Louis 
The size of the cells within each twig varied consider- 
ably; no one mother made all of the cells in her nest the 
same size; two of these mothers had two sizes of cells, 
five of them had three sizes, and two had cells of five 
different sizes. They varied from 44 to % inch. The 
thickness of the partitions varied from 1% to 15/16 inch, 
and the heavy plugs above the top cell in seven nests 
measured 3/16, 36, 14, 1, 114, 234 and 2% inches, while 
the vestibules were from 1 to 7 inches long. 
This wasp uses a large number of flies. One cell con- 
tained twenty-seven, by actual count; another with a 
half-grown larva still had seventeen. The great ma- 
jority were Agromyza parvicornis Loew. [J. M. Ald- 
rich]; a very few were the yellow Chiromeyia sp. One 
larva pupated June 19 and emerged as adult on July 4. 
The emergence of the young adults from their tiers 
of cells was watched whenever the opportunity was dis- 
covered. On April 1, one struggled upward and out of 
its twig. This was the top one in the stem, and from the 
last egg deposited. No others appeared until ‘April 29, 
when the next one emerged. From that date on to May 
11, six others arrived at their maturity and emerged in 
direct order of the sequence of the cells, from the upper- 
most downward, and in the inverse order of the deposi- 
tion of the eggs. On the first of May another nest was 
observed which, up to that time, had given forth no 
adults because all were dead excepting the occupants of 
the two lower cells. At this date one of these struggled 
upward through the entire mass of filling material and 
plugs and worked its way out to freedom; the other was 
not so successful, but was found dead where it had trav- 
ersed only part of the journey. Nevertheless, these did 
better than did their sisters of the species Odynerus con- 
formis which perforated their own partitions only and 
