102 INSECT ARTIZANS AND THEIR WORK 



have to pass through the bodies of their less-ready 

 kindred ; but if we are to judge by the behaviour 

 of another little carpenter, Osmia tridentata, there 

 is no likelihood of such action being taken. There 

 is such a thing as altruism among insects, though it 

 may be only instinctive altruism. 



Our native Osmia leucomelana usually drills out 

 the dead bramble-stems like Ceratina, and constructs 

 its cells of the pith, placing them end to end. 

 O. tridentata is a Continental species with similar 

 habits, and as it has been made the subject of some 

 interesting experiments by Fabre we select it for 

 description. Some other species are masons and 

 excavate sand or clay. Making a cylindrical boring 

 into the bramble-stem, O. tridentata does not 

 trouble to clear out at first more pith than will 

 serve to allow her passage. Then at the far end 

 of her burrow she constructs an oval cell, using 

 for the purpose the pith she has left on the stem, 

 and stores it with pollen, honey, and an egg. She 

 shuts up this cell by constructing another and 

 using the material cut out, mixed with salivary 

 cement, to form a partition across the stem. So 

 she proceeds until she has constructed and furnished 

 ten or twelve cells. 



Now, it is natural to assume that, as in some 

 similar cases, the egg that was deposited first would 

 produce the first bee ready to emerge, and a diffi- 

 culty arises as to the manner in which it makes 

 its escape. Dufour boldly concluded in a similar 

 case that it was from the last-made cell that the 



