HALICTUS. 
217 
burrow solitarily and apart from their congeners. In 
burrowing they form a tunnel which branches off to 
several cells, the excavations being as inartificial as are 
those of Andrena. Walkenaer tells us in his memoir 
upon the genus Halictus, that they line their cells with 
a kind of glaze, that they burrow in horizontal surfaces 
to a depth of about five inches, and which they polish 
very smoothly previous to covering it with their viscous 
secretion, and that the cells are all oval, the largest end 
being at the bottom. He says also that they burrow 
solely during the night, especially when the moon is 
shining, when it is difficult to walk without treading 
upon them; so numerous are they, indeed, that they 
look like a cloud floating close to the surface of the 
ground. Although burrowing thus at night, it is only 
during the day that they supply their nests with their 
provision of pollen and lay their eggs. Each of their 
cells is furnished with a small ball of pollen, varying in 
size with the species, but which never entirely fills the 
cell, and is affixed intermediately between both extremi¬ 
ties, and upon the mass contained in each cell they de¬ 
posit their small egg, which is placed at the extremity 
of the lump of pollen most distant from the entrance. 
The larva is hatched in about ten days, when it changes 
into the pupa. Some doubt attaches as to the length of 
time that the pupa remains before its transformation 
into the imago, and also as to the period at which this 
takes place. A peculiarity attends the appearance of 
the larger species. Some are very early spring insects, 
among which is the Halictus rubicundus; this I have 
seen in abundance on the first fine spring days collecting 
its stores on the flowers of the chickweed. It is then in 
the very finest condition, and it is really a very beautiful 
