50 HYMENOPTERA CHAP. 



a week or two, and so all get out. Frequently, however, the 

 emergence is prevented by something having gone wrong with 

 one of the outer Insects, in which case all beyond it perish unless 

 they are strong enough to bite a hole through the sides of the 

 bramble-stem. Thus it appears that whether a particular Osmia 

 shall be able to emerge or not depends on two things (1) whether 

 all goes well with all the other Insects between it and the orifice, 

 and (2) whether the Insect can bite a lateral hole or not; this 

 latter point also largely depends on the thickness of the outer 

 part of the stem of the bramble. Fabre's experiments on 

 these points have been repeated, and his results confirmed by 

 Nicolas. 



The fact that an Osmia would itself perish rather than attack 

 the cocoon of its brother or sister is certainly very remarkable, 

 and it induced Fabre to make some further experiments. He 

 took some cocoons containing dead specimens of Osmia, and placed 

 them in the road of an Osmia ready for exit, and found that in 

 such case the bee made its way out by demolishing without any 

 scruple the cocoons and dead larvae that intervened between it 

 and liberty. He then took some other reeds, and blocked the 

 way of exit with cocoons containing living larvae, but of another 

 species of Hymenoptera. Solcnius vagus and Osmia detrita were 

 the species experimented on in this case, and he found that the 

 Osmia destroyed the cocoon and living larvae of the Solenius, 

 and so made its way out. Thus it appears that Osmia will 

 respect the life of its own species, and die rather than destroy it, 

 but has no similar respect for the life of another species. 



Some of Fabre's most instructive chapters are devoted to the 

 habits and instincts of various species of the genus Osmia. It 

 is impossible here to find space even to summarise them, still 

 more impossible to do them justice ; but we have selected the 

 history just recounted, because it is rare to find in the insect 

 world instances of such self-sacrifice by an individual for one of 

 the same generation. It would be quite improper to generalise 

 from this case, however, and conclude that such respect for its 

 own species is common even amongst the Osmia. Fabre, indeed, 

 relates a case that offers a sad contrast to the scene of self- 

 sacrifice and respect for the rights of others that we have roughly 

 portrayed. He was able to induce a colony of Osmia tricornis 

 (another species of the genus, be it noted) to establish itself and 



