1917] Notes on Bombidce 281 



Every morning for about two weeks, I found that it was nec- 

 essary, in order to see the contents of the nest, to remove a 

 covering of grass, compactly held together by means of a mix- 

 tui"e of pollen and wax. This grass covering, or roof, made by 

 the bees naturally serves to keep light from entering the nest, 

 for general protection, and as an aid in keeping the temperature 

 within the nest constant. 



The Egg Stage of B. auricomiis. 



From this colony of B. auricomus, drones, workers, and 

 queens were reared, under observation, from the egg to the 

 adult stage. My notes show that the number of days in each 

 stage of development, in all three castes, is subject to variation. 

 Nutrition and temperature undoubtedly play a very important 

 part in the lengthening or shortening of the various stages. 

 The egg period varied from four to six days. No special, con- 

 sistent variation in the duration of the egg stage of the three 

 castes was noticeable, but additional data may prove the con- 

 trary. Mr. F. W. L. Sladen found that, as in the case of the 

 honeybee, eggs laid by workers produced drones. I was unable 

 to find out what finally happened to the worker eggs in this 

 nest, but I am sure that if the eggs ever hatched into larvae, 

 these larvae never reached the adult stage, on account of the 

 lack of food. As already stated, the eggs laid within short 

 intervals of each other, were laid in separate, adjoining cells, 

 and these cells were spread out over the cocoon or cocoons as a 

 single, more or less flattened mass. From the same egg mass 

 all three castes frequently emerged. 



The Larval Stage of B. auricomus. 



The larval stages of all three castes also present striking 

 variations in duration. The average number of days spent in 

 the larval stage for the three castes in this nest was as follows: 

 drone, eleven and three-fourths; worker, thirteen and a fraction; 

 queen, eleven and a fraction. Too few bumblebees of all castes 

 were carried through from the egg to the adult stage to enable 

 me to say that there is an average difference in the number of 

 days spent by the three castes in the larval stage. The larvae 

 grow rapidly, and usually after four days or more, spin silken 

 threads. As these silken threads hold together the thin walls 

 of their cells, they are essential to the existence of the larvae. 



