192 [January, 1869. 



much smaller in the Dactylopius than in the Lecaniuwi. In neither of 

 these instances are they arranged in groups, but then in some species 

 of Diaspina, in Leucaspis pini for instance, they are arranged not in 

 groups, but in the form of a semicircle around the vaginal opening. 



It may perhaps be suggested that if these ventral glands are 

 intestinal with digestive functions, they could not be situated, as often 

 appears the case (see fig. 2), below the anus ; but this, I think, is only 

 an appearance arising from a misconception of the true last segment 

 and which will be explained by my subsequent remarks upon this 

 segment. I have mentioned that these glands are not found on the 

 males, but this is not surprising, knowing that the functions of the 

 winged male are purely sexual, and that it has no mouth organs, and 

 only an atrophied abdomen. Lastly, I think it is not unusual for the 

 larva to be of less elaborate structure than the adult, which will explain 

 the reason of the organs being peculiar to the adult, and just as the 

 larva does not show such an elaborate completion of parts as the 

 adult, so perhaps we should not be surprised at finding some few 

 species of the Diaspina which are not provided with these ventral 

 grouped glands. Having now suggested what appears to me to be the 

 true nature of these grouped glands (glandules agminatee), I pi'opose 

 to offer a few remarks upon that part of the insect which has been 

 termed the last or anal segment. 



Perhaps the first and most obvious peculiarity of this segment 

 which is apparent to the student, is the remarkable variation in the 

 position of the anus appearing to violate the general zoological principle 

 as to its position. Prof. Comstock (p. 283) of course noticed this, 

 saying, " its apparent position is represented in the figures, and as 

 will be readily seen, varies greatly in different species." In the two 

 species which I have selected for illustration (see figs. 1 and 2), the 

 position of the anus will be seen to be abnormal. Instead of being 

 at the apex of the segment, in one case (fig. 1) it appears on the disc, 

 and in the other case (fig. 2) it is at the base of the segment. 



Now it seems to me that by observing the position of the anus 

 we should be directed towards a correct conclusion 'as to the position 

 of the true apex of the last segment, and this, I think, will lead to a 

 more accurate comprehension of the correct limits of this segment. 

 I should first mention that the part of the abdomen shown in figs. 1 

 and 2, as containing segments vii to xi, has hitherto been considered 

 as the last or anal segment, and it will be seen that on this pai*t only 

 are the spinning glands, as regards the Diaspina. Perhaps it is the 

 waxy nature of the scale substance continually exuding from this part 



