( cxcv ) 



Aculeates, Still I have noticed cases where as in the beautiful 

 Osmia ferruginea ( = igiieo-purjjurea) the colours of the $ are 

 decidedly richer and more intense than those of the (^, and 

 others in which the ^ is greenish (aeneous) and the ? dark 

 blue or violet {Osmia caeridescens, panzeri, versicolor, etc.). But 

 oftener there is little difference in the colour of the sexes, e. g. 

 in Sceliphron targionii and omissus (Fossors), and the majority 

 of Cerati^ia spp. (Bees). 



On the contrary, in the red-and-black (pigmented) forms, 

 whether with or without pictura albida, there is an undoubted 

 tendency for the $ to be the redder insect.* 



Thus, looking through my own collection, I find the ground- 

 colour of the abdomen black in all my ^,^, and more or less 

 largely red in all my $ ?, of the following species : — 



Fompilus unicolor, Salius notatulus, Calieurgus hyalinatus, 

 Sapyga quinqtiepionctata and siinilis, Elis sp. ?, Sphex pi'uinosus, 

 a/er, tristis, Gorytes niger (if I have associated the right $ with 

 this 1^), Palarus humeralis (here the " red " is rather " orange "), 

 Entoviosericus concinnus, Paracoelioxys rujiventris, Paradioxys 

 sp. ?, Phiarus abdominalis, Ammohates hiastoides and rostratus, 

 Biastes brevicornis and truncatus, and nearly every species 

 of Myzine. In many other cases — far too many to enumerate 

 — I find the abdomen of both sexes more or less red, but more 

 so in the $ $ than in the $$. And again in many other cases 

 and particularly in species of Andrena and Prosopis I find that 

 individual specimens of either sex may be black-and-red or 

 black entirely, but that the melanic forms are commonest 

 among males. 



Against these instances I can quote very few indeed of the 

 reverse phenomenon — (only one or two MutHlidae and Halicti). 



Red on the thorax is rare in Aculeates, but occurs in some 

 $Ants {e.g. several Formica spp.), and Mutillids, also in $ 

 Nomada spp. (of the rujicornis group, etc.), and in the sub- 



* I am not as yet prepared to say, whether there is any such tendency 

 in 9 9 of other groups than that now under consideration, or in cases 

 when the comparative redness or blackness of an insect is a question of its 

 pilosity and not of its integument. In some of the latter cases the rule, 

 if it exists, is certainly broken. Thus in British (though not in Continen- 

 tal) forms of two common Anthophora spp. the pilosity of the ? ? (except 

 their scopse) is black, while that of the (5 c? is hilvous. So that here the 

 9 cannot be said to be " the redder insect." 



