ANTHOPHORA AND SITARIS 79 



float uppermost in the honey, and round this surface are the 

 openings of the spiracles, so that the animal is adapted to 

 breathe while it floats passively upon the surface of the 

 honey which is its food. When it has finished the honey, 

 it is metamorphosed into a pseudo-pupa. Individual Sitaris 

 may vary in their subsequent life-history before reaching the 

 stage of the perfect insect, but we will leave these stages and 

 deal with those described. 1 The main adaptations here are : 

 the numerous eggs laid by the female, which meets the high 

 mortality among the larva; ; the three claws upon the legs, 

 which enable the larva to cling to the bee ; its emergence 

 from hibernation at the same time that Anthophora appears ; 

 the instinct to leave the male bee and go to the female, and 

 to leave the female and float upon the egg ; the equally 

 remarkable instinct through which it rigidly keeps within 

 the egg ; the metamorphosis into a shape, unknown among 

 other beetles, which is perfectly adapted to a passive exist- 

 ence floating upon the honey in the cell of the bee. 



Now some of the morphological adaptations might con- 

 ceivably have been brought about by mutations, though in 

 all of them it seems probable that ancestors of Sitaris that 

 first took to parasitism upon Anthophora, or the ancestor 

 of Anthophora, would have perished while waiting for tjae 

 mutation to occur, but the metamorphosis of the larva fmrrf 

 the triungulin to the vesicular form involves too mflcK to 



. . ' b .' 



be conceivable as the result of a mutation. This fiyn 

 larva is unknown among even allied forms, and the' 

 it is necessary on the mutation theory to assume 

 simultaneously got rid of all its appendages, assumed a 

 shape such that one surface must always float uppermost 

 in a fluid of the density of honey, and that the orifices 

 through which it obtained air were so placed that they 

 would be above the surface of the fluid upon which it 

 floated. The instincts without which the race would 

 certainly be exterminated, seem also inexplicable by muta- 

 tions. An allied form, Epicauta, lives upon the eggs of 



1 Fabrc, Souvenirs Entomoloyiques. 



