THE BIOLOGY OF THE MUD-DAUBING WASPS 33 



This nest that I was so fortunate to discover in course of con- 

 struction was in an accessible position so one could easily watch 

 the methods of building. It contained two complete tiers and 

 the third was being added. The wasp returned with a mouthful 

 of mud, but our presence disturbed her and she flew away. 

 Only on her fourth return was she content to settle down to 

 her work without heeding our presence. She would remove 

 the load of mud from her mandibles to her front legs and apply 

 it to the structure in its proper place and then smooth and 

 work it down with her head. Her mud puddle could not have 

 been far off, for she required only from one to three minutes 

 to make the round trip and bring her load of mortar. 



As usual, the male remained, in the tube that was being con- 

 structed while the female brought the mud and continued the 

 building. The male sometimes poked his head out of the cell 

 to meet or greet his spouse, in a way very similar to the habit 

 which we have seen in the smaller species of Trypoxylon (7\ 

 clavatum). A long pipe was first constructed. This was then 

 filled for a certain distance with spiders and an egg laid with 

 them and a partition put in, making a cell out of this section 

 of the pipe. This process was repeated until the entire pipe was 

 divided into cells, and then a second tier was made beside it. 

 Since most of these nests are built vertically, with the openings 

 downward, one wonders what prevents the spiders falling out while 

 the cell is being filled, the egg laid and the mud applied for the 

 partition. I have wondered whether the male did not in some 

 way perform this office. It was soon necessary for me to leave, so 

 we captured the female and took down the nest. We found the 

 male 'way up in the topmost corner of the unfinished tier. The 

 two older tiers were complete in every way, properly partitioned 

 and sealed, and each cell contained spiders and a young wasp. 



Dr. William H. Ashmead 6 says:"Walsh was the first to record 

 the habits of Trypoxylon albitarsis, which usually selects the 

 deserted cells of a mud-dauber (Pelopoeus) in which to nidificate, 

 provisioning its cells with spiders. I can confirm this statement 

 of Walsh's from personal observations, as I have not only ob- 

 tained them from the old cells of Pelopoeus but also from those 

 of Chalybion caeruleum. I have also bred T. clavatum from 

 the same mud-dauber's cell." 



6 The Habits of Aculeate Hymenoptera, II., Psyche, Vol. VII. p. 45. 



