08 BEES AND WASPS [OH. 



the warm months of the year from April to as late as 

 early October; and many (perhaps all) are to be 

 found at the beginning and again at the end of the 

 season. They are very partial to composite flowers 

 such as dandelion, hawkweed, etc. 



Some of the species of this genus are of special 

 interest in showing a tendency towards the social 

 condition. Fabre's observations on H. lineolatus and 

 H. sex'cinctus establish that there is considerable 

 collaboration between the members of a colony. A 

 number of individuals work together in sinking a main 

 shaft which branches out into side galleries beneath 

 the earth, the galleries leading to various groups of 

 cells. Each such group is the work of one female ; 

 so that a considerable number of nests are served by 

 one and the same entrance and corridor. A sentinel 

 is often stationed at the entrance, and there is close 

 behind the doorway a small recess into which the 

 sentinel can step whenever she wishes to allow a 

 member of the establishment to pass in or out. The 

 seasonal distribution of the sexes of Halicti is sure to 

 strike any observer or collector of these insects: in 

 the spring females only are to be found, while later 

 in the year there is an astonishing preponderance of 

 males. The explanation of this circumstance shows 

 a further step towards the habit which prevails among 

 the social bees. The females that appear in the 

 spring have hibernated in their burrows, but not after 



