158 BULLETIN OF WISCONSIN NATURAL HISTORY SOCIETY. VOL. 3, .NO. 4. 
der certain circumstances the larvae of one of the species were 
observed attacking each other. Undoubtedly the degree of toler- 
ance varies in the different species. The most tolerant of the 
species under consideration proved to be Ceratina dupla Say, 
a bee suffering to a great extent from the presence of two 
Ichneumonid parasites in its nests. The tolerance displayed by 
its larva towards the larva of one of these Ichneumonids (Habro- 
cryptus graenicheri Yiereck) has been pointed out in a previous 
paper. (8.) 
On July 9th, 1903, several cells of Ceratina dupla were pro- 
vided each with two eggs, without increasing the food supply. 
In two of the cells the larvae lived long enough to develop into 
pupae on August 4th, and from one of these cells two female 
bees made their appearance, from the other a male and a female. 
These specimens were naturally much smaller than the average 
bee of this species since the larvae had been brought up on half 
rations. Not one of these larvae, while living close together, was 
ever seen to make an attack on the other occupant of the cell. 
This was not even done at the critical period when the food 
supply had become exhausted before the larvae had reached their 
normal development. 
Four larvae from a nest of the leaf-cutter bee, MegacMle 
infragilis Cress, procured at Cedar Lake, Washington Co., on 
August 1st, 1905 were experimented with in the same manner 
as the Ceratina larvae. They never attacked each other. But 
when the two larvae in the comparatively narrow cell had grown 
to such an extent that there was not room enough for both of 
them, one was crowded out by the other, and died. This hap- 
pened in both cells under observation. 
From a nest of Osmia atriventris Cress., found in the same 
locality, and on the same date, three larvae of different size were 
taken out of their cells, and placed on a portion of bee-bread. 
They were brought face to face to each other, and so close to- 
gether as to be in each other's way, especially after increasing in 
size. These larvae never showed any signs of hostility towards 
each other, but arranged matters by taking up new positions on 
the bee-bread so as to interfere less with each other when feeding. 
The results obtained with the larvae of Alcidamea producta 
differed in some respects from those discussed above. Being 
well supplied with material I was enabled to make repeated ex- 
periments with these larvae last summer (1904), as also this year. 
8. S. Graenieher. Entomological News, Vol. 16, p. 43 (Febr., 1905). 
