^^ AND ^^/?^^ 



JOURNAL OF VARIATION. 



No. 9. Vol. IV. September 15th, 1893. 



Jiii. Explanatory Suggestion of the Plumose ./IriteniioS iii 

 tlie female Lepidopterous Pupa. 



By J. H. WOOD, M.B., F.E.S. 



Those of us into whose hands Mr, Poulton's beautifully illustrated 

 paper on the Lepidopterous jjujia has fallen, must have felt o-reatly 

 indebted to him for opening a little-known field, and bringing many 

 curious and unexpected facts to our knowledge. But whether we are 

 prepared always to agree with his explanations is not so clear. For 

 instance, it must have struck many of his readers that the double wino-_ 

 line might be simply the margin of the fringe and membranous win^- 

 respectively ; but the question is in the hands of my valued friend 

 Dr. Chajunan, Avhose thoroughness in anything he undertakes is 

 proverbial. My object, however, is to draw attention to a still more 

 interesting fact recorded in that paper, namely, the complete sculpturino- 

 of plumose antennas on the female pupa, when in the perfect insect the 

 male only possesses them, and to offer a simpler and, I venture to think, 

 a more satisfactory explanation than the one given in the paper. 



I would premise in the first place, that although, strictly speakinc-, 

 the antenna? can scarcely be called secondary sexual organs since they 

 probably serve some general purpose, yet that there is a sexual side to 

 them cannot be doubted, if we consider their highly si^ecialised condition 

 in many male insects. Next, turning to the highest of all animals, the 

 Mammalia, we find that the mammary gland, from which they derive 

 their name, is present in both sexes, but is only comj^letely develoj)ed in 

 the female. Moreover, it is a curious and well-known fact, that in boys 

 at the advent of puberty, these glands become painful and enlarge, just 

 as they do in girls at the same age, and we should infer, but that we 

 know from experience it will not be so, that they were going to develop 

 equally in both. Cloing back again to the insect, the larva may be 

 considered the child, the perfect insect the adult, and the pupa the ao-e 

 of commencing puberty ; the analogy, so far as sexual life is concerned 

 being strictly accurate. If then in the mammal the stimulus of awaken- 

 ing sexual development is so excessive or so ill-directed as to rouse 

 into temporary activity and growth an organ that afterwards fails to 

 develop, what should hinder the same thing from taking place in the 

 insect, with only this accidental difference, that, whereas in the pupa 

 the external parts are laid down in a hard imjDerishable material, the 



