( clxxiv ) 



feature existing, rudimentarily at least, in the ^ ^ also, and 

 some of the few 9 characters which can really be called 

 paradoxical, and which stand in evident relation to definitely 

 female activities, appear, after development in that sex, to 

 have been transmitted more or less completely to the other 

 sex also. 



(5) A rule which Darwin has described * as one of " high 

 generality," and as " applying very strongly to Secondary 

 Sexual characters," is stated by him as follows : — " A part 

 developed in any species in an extraordinaiy degree or 

 manner in comparison with the same part in allied species 

 tends to be highly variable." I cannot satisfy myself that 

 this rule applies, at all generally, to the Sexual characters 

 of the Aculeates. Some of the most paradoxical ^ characters 

 of antennae, legs, etc., are anything but variable : — they agree 

 through long series of specimens literally to a hair. Nor can 

 I see, that the excessively developed pollen-bearing $ apparatus 

 in certain genera of Bees {Dasypoda, Bomhus, Apis, etc.) is 

 at all more variable than the corresponding parts in Frosopis, 

 Sphecodes, etc., which are scarcely modified at all for that pur- 

 pose. Exceptionally, I admit, certain paradoxical characters, 

 both of (^ cJ and $ 9 (as the genal spines in some Andrena ^ ^ 

 and the abnormally developed mandibles of Osmia latreillei $), 

 are extremely variable. But, on the whole, I do not find 

 that there is any correspondence, in this group, between the 

 greater or less abnormality of secondary sexual characters and 

 their variability in individual specimens. 



(6) Nor do the sexual characters of Aculeates appear to 

 me to follow another rule laid down in the Origin of Species,'\ 

 viz. that "the secondary differences between the two sexes 

 of the same species are geneially displayed in the very same 

 parts of the organisation in which the species of the same 

 genus differ from each other." For instance, the most obvious 

 secondary difference between the sexes of any V^espa or Halictus 

 species is the much greater length of the ^ antennae. But in 

 separating species of Vespa or Halictus from one another the 

 antennae scarcely help us at all : the characters useful for 



* Origin of Species (Popular Edition), p. 111. 

 t !bid., p. 115. 



