18 ME. A. HAMMOND ON THE 



Humble-Bee from Packard *. In the first of these the fifth seg- 

 ment of the body, the thoracico-abdominal segment of Newport, 

 is seen to follow the alary segments and to be very similar to the 

 succeeding abdominal ones, differing only from them in the form 

 of its oblong spiracle, by which, however, it is easily and certainly 

 recognized in the succeeding stage, where it is seen that the tho- 

 racic abdominal incisure has taken place behind it, including it 

 with the thorax. If further evidence be required, I would point 

 out that the Hymenoptera are not so exceptional in this matter 

 as may be thoughtf, and that the Coleoptera, as a rule, if not also 

 the Heteropfcera, exhibit a similar structure. That the Coleo- 

 ptera do so has long come under my notice ; and I believe Audouin 

 pointed out the same thing. If we look at the dorsal surface of 

 Rhizotrogus, Geotrupes, or JDyticus, we find in either case the 

 dorsal plate of a segment whose ventral arc has disappeared (the 

 segment is ventrally atrophied). This dorsal plate is unmis- 

 takably the first of the abdominal series, and furnished, like all 

 the succeeding ones, with a pair of spiracles, differing from the 

 others chiefly in being larger. It is quite distinct from the meta- 

 thorax, following, as it does, the inwardly developed and obtusely 

 triangular postscutellum (see PL II. fig. 15, for postscutellum of 

 Rhizotrogus). In default of its own ventral arc, however, it is 

 thrown forward, as it were, upon the dorsal surface of the meta- 

 thorax, or the ventral surface of that segment is produced under- 

 neath it so as to supply the place of the lost ventral arc. It is as 

 if the great development of the ventral surface of the metathorax 

 had absorbed that of the next segment. A like conformation, I 

 believe, prevails in many Heteroptera. Newport +, I ought to add, 

 has noticed a general atrophy of the fifth segment of the larva in 

 insects, though he does not appear to have connected it with the 

 ventral atrophy of that segment in the imago to which I have re- 



* " On the Morphology of Insects," Proc. Boston Soc. Nat. Hist., Feb. 1866, 

 p. 282, and the figures on p. 294. 



t I cannot quite understand how it is that Packard seems to have ignored 

 this fact ; for, in the paper alluded to in the previous note, he says (p. 291), 

 " The Hymenoptera differ from all other insects in having the basal ring of the 

 abdomen thrown forward upon the thorax." The phenomenon is, I admit, not 

 so strikingly marked in the two other orders as in the Hymenoptera ; still 

 it is, I venture to think, very pronounced, as I have endeavoured to show. 

 Amongst the Heteroptera I would adduce the case of Coreus marginatum as the 

 result of my own observation. 



\ Todd's Cyclopaedia of Anatomy, " Insecta," p. 28. 



