588 Insects. 



social communities, on the contrary, we find instances of the closest 

 resemblance, as in Bombus and Apathus. 



Early in April, 1841, I visited the spot where I had found Eucera, 

 for the purpose of digging up a quantity of the cocoons ; these I 

 found at the depth of about eight inches, in a stiff clayey soil. At 

 this time the Eucera had, in some instances, just changed to the pupa 

 state, — whilst the Nomadae which I found in some of the cocoons 

 were perfect in colouring, and towards the end of the month quite 

 active, as I found upon liberating some of them : in one instance I 

 saw two Nomadse come out of the same cell, which might also have 

 been the case in other instances where I did not observe them escape. 

 My observations lead me to the conclusion that the eggs of Nomada 

 are hatched first, and that the food is all devoured previous to the 

 larva of the Eucera being hatched. I admit the possibility of the 

 Nomada watching the precise moment when a sufficient quantity of 

 provision is stored up, and depositing her egg before the bee, and 

 then closing up the burrow, but I never saw an instance of a Nomada 

 remaining at the mouth of the burrow for such a purpose ; there is 

 also a possibility of the parasite removing or destroying the egg of 

 the bee : this is a point in the economy of parasites which I hope by 

 diligent observation yet to clear up. The different species of Nomada 

 by no means confine themselves each to the nests of one particular 

 species of bee, wherein to deposit their eggs ; thus the Nomada 

 Sheppardana infests the nests of Colletes and Andrena, — N. ruficornis 

 the nests of Andrena fulva, and of Andrena tibialis : future observa- 

 tion will, I have no doubt, prove that the parasitic bees merely con- 

 fine themselves to such species as provide a suitable supply of food 

 for the young of the parasite. 



This is an extensive genus of bees. Mr. Kirby has enumerated 

 thirty-one species, but it will be seen that in two instances only has 

 he combined the sexes under the same name : when this is carried 

 out as far as observation and subsequent discoveries will enable us, 

 we shall find the total number greatly reduced. Mr. Shuckard has dis- 

 covered several species not previously known to be British ; I have dis- 

 covered the Nomada Roberjeotiana of Panzer, as well as an entirely 

 new species described under the name of N. baccata (Zool. 409) ; and 

 Mr. Newman has discovered another, first described in the present 

 paper. The species of this genus —like those of Vespa, Cerceris, 

 Crabro, &c, and other banded and maculated insects — are subject to 

 great variety in the markings, a circumstance which has led to an 

 unnecessary multiplication of species : in more than one instance I 



