20 
BRITISH APHIDES. 
somite, Professor Huxley^ makes certainly five, and 
hypotketically six. Three are in the thorax, and, 
according to Kewport and Westwood, there are eleven 
in the abdomen. This number also is ascribed to 
the Hemiptera Heteroptera by Messrs. Douglas and 
Scott. t Whilst Huxley considers that the last somite 
in Aphis is abortive, as in some other orders, like the 
Lepidoptera, &c., Balbiani | thinks it is represented 
by the Cauda, which in some genera is an organ of 
considerable size. 
Kaltenbach,§ in his excellent monograph, and 
Patzeburgll also, considers that there are only nine 
abdominal rings in Aphis. More recently M. Lacaze- 
Duthiers, by generalising over various orders of 
Insecta, concludes that the different forms of stings, 
borers, and ovipositors are all modifications of the 
ninth abdominal somite. He shows that the vulva of 
insects always opens between the eighth and ninth 
somites, and also that, in most Hemiptera, three 
somites intervene between the vulva and the anus, 
which last orifice is always placed at the very ex- 
tremity of the body. Balbiani incidentally only dis- 
cusses this question, as to the segmental system of 
the genito-anal region of Aphis, but he considers that 
a comparison of the corresponding region of the 
female parts, with that of the male, leads to the con- 
clusion, that all these parts are comprised in three 
abdominal segments, and therefore suggest a unity 
of composition, quite in harmony with the views of 
Lacaze-Duthiers and Professor Huxley. The last phy- 
siologist considers the penis to be a modification of 
the tenth somite. Balbiani regards the vulva as 
* Huxley, “ On tlie Morphology of Aphis,” ' Trans. Linn. Soc.,’ vol. 
xxii, Part 3, p. 230. 
f ‘ Ray Soc.,’ vol. for year 1865. 
J Balbiani, “ Meinoire sur la Generation des Aphides,” ‘ Ann. des 
Sciences Naturelles,’ 1 ser., t. xi, p. 64. 
§ Kaltenbach, ‘ Monographic der Pamilien der Pflanzenlause,’ 1843, 
p. xiv. 
II Ratzeburg, ‘Die Forst Insecten,’ Berlin, 1844. 
