THE ENTOMOLOGIST. 175 
day of spring and continuing to the end of August. The 
black-faced male appears with Parvula at the end of March 
or beginning of April, and lasts till about the end of May. 
In the middle of May are to be found white-faced males, and 
the female Nana; and, at the end of June or beginning of 
July, there is another white-faced male, which differs from 
the previous one, and with this male appears a female, which 
at first sight might be mistaken for Parvula; but, as Kirby 
says in a footnote, the abdomen is of a different shape, and 
it is less hairy. These three species, being found in 
abundance close to the city, have enabled me to get a good 
series, with the dates of capture; and a close examination of 
these has led me to believe that Kirby was right in his belief 
of the three species. 
Amongst the early bees is found one whose habits are 
veiled in mystery; it is a bee without the necessary hirsuties 
for conveying pollen, ‘These are invariably absent in the 
parasitic bees, but it does not necessarily follow that all bees 
without these appendages are parasitic; for example,—the 
genus Prosopis, or Hylzus, is entirely without them, but are, 
nevertheless, constructive bees; the parasilic bee lays its 
eggs on the honey and pollen collected by another bee, when 
it finds one suited for its purpose. Many of these parasites 
are constant in their attacks on certain species of constructive 
bees; others (of which perhaps the best example is Nomada 
ruficornis) attack several species varying greatly in size, and 
consequently in the quantity of honey and pollen they collect 
for the future young. The Nomada vary in size according 
to the species they attack, the size being influenced by the 
quantity of food. ‘Tbe above-mentioned insect varies from 
three to six lines. Asa rule there is not a great variation in 
the size of the constructive bees, but amongst the Sphecodes 
there is just the same variation in size as there is in the 
Nomade ; these insects are generally found running or flying 
about the dry banks infested by the Halicti, which, in the 
different species, vary as much in size as the specimens do 
in the species of Sphecodes. 
And it is not Halictus only that Sphecodes attacks (that is 
supposing it to be parasitic), for in May last I found a large 
colony of Andrena albicrus, which had made their holes in 
the hard ground by the sile of a road, and flying about the 
