CHAPTER III 

 SOME FLY-CATCHING WASPS 



Hypocrabro stirpicolus Pack. [S. A. Rohwer]. 



An old railroad tie lay half buried in a heap of dirt. 

 Under the protruding rotten end was a miniature hill of 

 sawdust, or rather particles of wood bitten out, and above 

 this a clean-cut hole pierced the log. We found after we 

 began digging into it that only a small portion of this was 

 rotten, and under the surface the wood was very hard. The 

 long tunnels leading in from the surface aperture were 

 made in the softer, decayed part of the wood. This tunnel 

 led to a series of three cells which were five mm. in diam- 

 eter and were partitioned to make neat cells fifteen to eigh- 

 teen mm. long. Another tunnel branched off from the main 

 channel, and, going into a lower stratum of wood, there 

 branched into four similar cells as shown in fig. 21 (slightly 

 enlarged), each containing a definite successive stage in the 

 development of the young. The material used for partitions 

 was the sawdust tightly packed to a thickness of ten mm., 

 so it made a remarkably strong wall. 



The prey in these cells was two-winged flies of several 

 species. Two cells that were filled and had very small larvae 

 had four flies each, and another had four flies plus one head. 

 In some cells were many heads, wings and thoraces of flies. 

 One cocoon was of a dark brown color, and all the debris 

 in the cell had been shoved to one end before spinning (fig. 

 22). Two adults emerged on July I and 3. 



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