February, 1889.] 193 



which has had a material effect upon its composition, for whilst it is 

 of a different colour to the remaining part of the body, being usually 

 of a bright yellow colour, it also (as Comstock has observed) appears 

 to have become chitinized, and it preserves its characters so well, that 

 even after a specimen has been kept a year or two in the cabinet, it 

 still affords all the characters required for specific determination. I 

 am now going to suggest that this part of the abdomen, in the 

 Diaspina sub-family, consists really of five segments much modified 

 in shape, and of which the divisional lines have become suppressed, 

 and I will endeavour to point out the circumstances which have finally 

 led me to this conclusion. 



If the insects are examined alive and in different stages of mi- 

 croscopical preparation, very frequently traces of the obliterated 

 somital divisions will be found, and perhaps the best instance for 

 observing this will be found on examination of the second stage of 

 Leucaspis pini, as shown in fig. 3. In this species the lower part of 

 the abdomen will be found to be, as is usually the case with the 

 Diaspina, of a bright yellow colour, easily distinguished from the 

 remaining part of the insect, which in this species (second stage) is of 

 a dark brown, almost black colour, and the yellow part when examined 

 is fonnd to consist of five segments, as shown in fig. 3. Indeed, if 

 this part of the abdomen were considered as one segment only, it 

 would be difficult in most species of Diaspina to understand what had 

 become of the remaining segments, in order to make up the normal 

 number of eleven, or even of nine, as a reference to Signoret's artistic 

 figures will I think show (see also plate ii, Ent. Mo. Mag., vol. xxv). 



Doubtless it is by no means unusual for the last few abdominal 

 segments to have become much modified in many insects, and rendered 

 subservient, as it were, to the genital organs, but I believe that usually 

 traces of the missing segments can be found, although not always 

 externally. This is shown in the allied family of Aphides by Prof. 

 Huxley in his " Agam., Bep. and Morph. of the Aphis " (Trans. Linn. 

 Soc.', vol. xxii, pi. 39), and I have found that remarkable species 

 Cerataphis latanice (described and figured by Mr. Buckton in his 

 " Brit. Aph.," vol. iv, p. 198, pi. 134) useful for comparison as to last 

 segment, whilst the aculeate insects of course afford good examples of 

 modification of the terminal segments. Targioni-Tozzetti appears to 

 have recognised to some extent this last segment modification amongst 

 the Lecanina sub-family, for he terms the "anal cleft," which is 

 characteristic of this sub-family, " the caudal," whilst he describes the 

 terminal lobes as the "precaudal segment" (see his fig. 30, tab. 1). 



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