( clxxi ) 



authorities include the Chrysids, and I should not have been 

 sorry to do so here ; but I find that the four groups universally 

 reckoned as Aculeate (namely Ants, Fossors, Wasjjs, and Bees) 

 will more than occupy all the time at our disposal. Indeed I 

 am not sure that it would not have been wiser for me to 

 exclude the Ants also, and limit myself to the more homo- 

 morphic trio of Fossors, Wasjys, and Bees. But I did not 

 realise this until my work had proceeded so far that it seemed 

 too late to start afresh on a new plan. Accordingly, by 

 "Aculeate Hymenoptera" I mean, for present purposes, 

 (1) Ants, (2) Fossors, (3) Wasps, and (4) Bees. 



It may make what I have to say more intelligible on a 

 first hearing if I reverse the order which I should have pre- 

 ferred if this had been, not an Address, but a Monograph, and 

 state first the general impressions left on my mind after as 

 complete a survey as I have been able to make of the various 

 ways in which the sexes of Palaearctic Aculeates differ, and 

 afterwards some of the facts — not, of course, all, but such as 

 seem to me the most curiovis or otherwise interesting — on 

 which those impressions depend. Few, if any, of these fahts 

 are actually new, though at present they are for the most 

 part recorded only in systematic works which none but 

 specialists are likely to have consulted. And I may add that 

 though I can claim no originality for my observations, at 

 least they rest upon " Autopsy," i. e. except where I state the 

 contrary, you may take it that I have examined the phenomena 

 in actual specimens, and generally in long series of specimens, 

 and that I am acquainted with almost all the Insects to be 

 mentioned, in nature, and generally in life, and not merely in 

 literature. 



(1) I remark, first, that, whenever we know the life-history 

 of both sexes of an Insect belonging to any of these groups, 

 there is generally an obvious probable explanation, on the ground 

 of Utility, to be given of the characters of one sex ; and that 

 the sex — whichever it be — which shows the useful characters, 

 is the sex which, in that respect, has departed furthest from 

 what Darwin calls " the type," i. e. from the normal characters 

 of its ancestors and nearest relatives. Accordingly, the 

 phenomena, as I interpret them to myself, quite support 



