( clxxxv ) 



9 ? of their own species. He finds * that this fragrance 

 proceeds from the head ; but its use is no doubt analogous, 

 though the manner of production diifers, to that of the 

 scent-scales in certain $ Lepidoptera, which have been made 

 familiar to most of us by the investigations of Dr. Dixey and 

 Dr. Longstaff. 



(4) Another curious group of ^ characters occur in the 

 ventral-plates, and the apical and subapical dorsal-plates, of 

 the abdomen. Some of these, however, are not external 

 characters, the plates exhibiting them being "telescoped" 

 out of sight ; and others are so evidently connected with the 

 structure and position of the Reproductive organs that I will 

 not now discuss them. But some even of the hasal ventral - 

 plates are paradoxically formed in many Aculeate ^ ^, e.g. 

 spp. of Palarus, Stizus and Bemhex (Fossors), Masaris (Wasps), 

 Osmia, Eriades, and Halictoides (Bees). Also, the apical 

 <iorsaZ-plates show strange characters (teeth, spines, excisions, 

 foveations, etc.) in some $ $ oi Bees and Fossors, as Cerceris, 

 Anthidium, Osmia, Megachile, Eriades, and especially Coelioxys. 

 Their ? $ show no such characters. (But it may be remarked 

 that in the Chrysids we find similar characters occurring as a 

 rule in both sexes equally, a fact for which, so far as I know, 

 no explanation has ever been suggested — nor can I suggest 

 one.) 



The $ abdomen in Aculeates normally shows one more 

 fully chitinised dorsal-plate than that of the ? (7 against 

 6). This, like the corresponding difference in the number of 

 antennal joints, is not characteristic of Hymenoptera generally. 

 For in Sawflies the ? shows one more dorsal-plate than 

 the $ (8 against 7), and in Chrysids there are generally 

 three such plates only in both sexes, except in Cleptes ((^ 5, $ 4) 

 and Parnopes ((^4, $3). This is rather a question of the 

 "telescoping" of segments one within another than of their 

 actual number, and can hardly be discussed without reference 

 to internal characters and the structure of the Reproductive 

 System, so I pass it over, and proceed to consider external 

 characters peculiar to females. 



(1) Their sense-organs (eyes and antennae) generally show 



* Sladen, The Humble Bee (Macmillan, 1912), p. 13. 



