( cxcix ) 



streaks or broad bands on a dark ground are produced in some 

 Aculeates (e.g. Mutillidae, Melecta and Crocisa spp., Halictus 

 scabiosae, etc.) mainly by the pilosity, in others (as Co'abronidae, 

 Cerceris spp., Nomada, and Anthidium, as well as in most 

 Wasps) by staining of the body itself. Although most of 

 these Pilosity-characters are probably Protective and not 

 Sexual, some, I think, are pretty clearly of the latter sort. 

 Among such may be probably leckoned the conspicuous white 

 tuft of hair on the clypeus in several S 6 ^^ Andrena, and the 

 silvery faces of some $ Fossors, though it is true that in other 

 cases in this Group the character is nearly equally well 

 developed in both sexes. In one remarkable instance a 

 character peculiar to $ ? appears to be Sexual and Protective 

 also. I refer to the glittering white or yellow round spots 

 of dense pilosity (arranged almost like the "pips" on dice or 

 dominoes !) which occur on the abdomens of females only in 

 many species of Mntilla, and are the more conspicuous because 

 the actual integument in all these species is, in that sex, 

 entirely black. The number and disposition of these spots 

 vary according to the species, and are much relied upon as 

 specific characters, but so far as I know they are absolutely 

 confined to $ 9- It seems practically certain that these spots 

 are a case of Warning-colours (Aposematic). The insects 

 must be anything but an agreeable morsel to most Insectivora. 

 Their integument is excessively hard, and their juices probably 

 very unpalatable ; for it is difficult to pin them, and when 

 pinned they exude a gi-eat deal of what is commonly called 

 "verdigris" (= oleate of copjjer according to the late Dr. 

 Knaggs). Also they sting terribly. And lastly, being 

 apterous they are exposed to dangers which their J $ can 

 escape by flight. Hence there is good reason that they should 

 exhibit special Danger-signals, lest they should be mistaken 

 for some unobjectionable insect of another kind. 



But I have already occupied more of your time than the 

 occasion justifies, though I am far from having exhausted my 

 subject, or even alluded to certain branches of it, which I 

 should wish to discuss if it were possible — as the pigmentation 

 of Aculeates' eyes which is sometimes different in the two sexes, 

 and has hardly been noticed except in a few records made by 



