258 BRITISH HYMENOPTERA. 



mixed colony of the Haliclus abdominalis, 'Andrena nigro-cenea, Halictus morio, 

 Sphecodes subquadratus, and S. Geoffroyellus ; this being at a short distance 

 from my house, I had an opportunity of frequently observing their economy; 

 my visits to the colony were frequent, and I made close observations of the 

 proceedings of the bees; yet, notwithstanding, I could not in a single instance 

 detect the Sphecodes entering the burrows of Halictus; those into which the 

 former bee entered were of a smaller diameter than those of Halictus, in fact 

 intermediate in size between the burrows of H. abdominalis and H. morio — 

 too small to have admitted the female of abdominalis. These proceedings were 

 observed on several occasions; no males of any of the bees were to be seen 

 at this time, those of Andrena having disappeared some time, and those of 

 the Halicti not being developed. On visiting the colony one cloudy morning, 

 I was much delighted to observe the head of one of the species of bees at 

 the mouth of most of the burrows — the female Halicti at their own burrows, 

 and Sphecodes also at their own. The result of my observations of this colony 

 led me to believe, still more firmly, that Sphecodes is not a parasite. Since 

 the time when the above observations were made, I have on several occasions 

 detected Sphecodes busily engaged in forming her burrow, a fact which I con- 

 sider conclusive of the correctness of the opinions above stated. 



Genus Halictus. 



The economy of this genus of Andrenidce does not appear to have been 

 ascertained previous to my own observations being published in the year 1850: 

 it is so remarkably different to that of all other solitary bees, except of those 

 belonging to the genus Sphecodes, that I am surprised it had escaped the 

 researches of my predecessors, who, like myself, "have loved to hear the wild 

 bee's hum." It will be observed that the females of Halictus and Sphecodes 

 make their appearance in June, and are to be found from that time until late 

 in the autumn; but no males of these genera will be observed until long after 

 the appearance of the females; my observations on a colony of H. morio will 

 serve as the history of the whole genus, making allowance for the different 

 periods of their appearance. "Early in April the females appeared, and con- 

 tinued in numbers up to the end of June; not a single male was to be found 

 at any time. During the month of July scarcely an individual could be found, 

 a solitary female might now and then be seen, but the spring bees had almost 

 disappeared. About the middle of August the males began to come forth, and 

 by the end of the month abounded; the females succeeded the males in their 

 appearance about ten or twelve days. These industrious creatures immediately 

 began the tasks assigned to them, burrowing and forming their nests; one of 

 their little tunnels had usually others running into it, so that a single common 

 entrance served as a passage to several cells, in each of which a little ball of 

 pollen was formed, and a single egg deposited thereon. The larva? were usually 

 ten or twelve days consuming it, by which time they were fully fed; in this 

 state they laid until they changed to the pupa? state, when they very shortly 

 became matured." I have reared individuals of H rubicundus from the egg 

 to the perfect insect; on the 15th. of July I procured cells containing the 

 pollen balls with an egg on each; in twelve days the larva? were full-fed; the 



