NESTING HABITS OF SOME AXTHIDIINE BEES. 



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nest 8 also. Presently the owner backs out and is followed 

 closely by the intruder. The former alights on the intruder's 

 thorax, biting with the mandibles at the junction of head and 

 thorax. A short, lively tussle follows, after which the intruder 

 escapes and the owner goes on working. 



Example 2. 



Sept. 17, 1926. Bee D, which has been constructing nests 3 

 and 4, has now spent ten minutes carrying chaff, etc., into 4. 

 In the meantime, bee /, which has been working on nest 8, 

 arrives from one of her numerous trips to the field and goes into 

 nest 3. She at first makes regular trips carrying soil out of 

 this nest. Then she seems to be carrying pollen in. The owner 

 of nest 8 has been working on 3 all day and has but rarely visited 

 8. The owner of nests 3 and 4 has continued to carry chaff, 

 etc., solely into 4, eventually plugging it up. The next day 

 the owner of nest 3 returns. The owner of nest 8 sees her return 

 and so is now working as before on 8 (c). 



Five bees by this time (Sept. 17) have been seen repeatedly 

 to visit two nests apiece. To summarize, they are: (i) Bee C 

 to nests i and 2; (2) Bee D to nests 3 and 4; (3) Bee E to nests 

 5 and 14. (4) Bee / to nests 8 and 3 (to 3 only to-day) ; (5) Bee 

 H to nests 6 and 7. There are eight bees working in the colony. 

 Of the sixteen nests, nine are open and seven are plugged, but 

 of the latter, numbers 7, 15 and 16 are not being worked upon 

 by the bees. Thus the eight bees of the colony are working on 

 thirteen nests, and three of these bees are seen to work on but 

 one nest apiece (c). 



On September 26, we dug up the colony and found 151 com- 

 pleted cells from the 16 nests, which is an average of 9.44 cells 

 to a nest. This was practically the end of the nesting season, 

 for at this time and later the colonies of D. sayi were deserted. 



It is interesting to note, from a standpoint of comparative 

 entomology, that a wasp, Sphex varipes (Cress.) l has been 

 observed to be taking care of two nests also (h). 



From these facts and others in our study of bees, we have 

 found that there is sometimes considerable variation in the 

 habits of different individuals of a given species. 



1 Kindly determined by Mr. S. A. Rohwer. 

 18 



