1889.] 189 



OBSEEVATIONS ON COCCIDJE (No. 3). 

 by albert c. p. morgan, p.l.s. 



Caudal Segments and their Appendages. 



If reference be made to the female forms represented on Plate II 

 (ante), what is usually termed the last or anal segment will be found 

 to have undergone considerable modification as regards shape, in com- 

 parison with the other segments, and to be further characterized by 

 marginal fringes and emarginations, as well as by tubular and simple 

 caecal openings on the disc. I purpose now to consider briefly this 

 remarkable anal segment and its appendages. 



Taking first the Diaspina into consideration, on the dorsal side of 

 the insect will be found several rows of tubular glands (Plate III, 

 figs. 1, 2), and also around the margin several simple csecal openings, 

 which, in some instances, appear to have a callous margin as in Mytil- 

 aspis pomorum (fig. 2). Besides these, there are also some isolated 

 scattered openings on the disc. These may all perhaps be considered 

 as spinning glands, or dorsal spinnerets, which secrete the substance 

 from which the scale is formed. In the Lecanina the principal 

 spinning glands will be found on the dorsal margin, at the junction of 

 the thoracic with the cephalic and the abdominal segments, and they 

 consist of round pores or follicles amongst which are two short cone- 

 shaped villi, and between these is a long stout spine (see fig. 5). In 

 the Coccina a group of similar spinning glands will be found on the 

 lateral dorsal margin of each of the segments (see fig. 4), amongst 

 wbich arise, as with the Lecanina, two cone-shaped' villi (see fig. 8), 

 and from each of these groups on each segment (taking Dactylopius 

 citri as a type of this sub-family) emanates a powdery white projection, 

 very noticeable during the life of the insect, and numbering 17 on 

 each side of the insect. These dissolve in alcohol, and leave no trace 

 beyond the glands and villi before mentioned, except on the last 

 (exclusive of the ano-genital ring) segment, where a long spine will 

 be found. 



But in addition to these scale-substance secreting glands, whose 

 openings are on the dorsal side of the insect, there will be found on 

 the ventral side in most species of Diaspina, but not in all, four or 

 five, and sometimes more, groups of glands which present a different 

 appearance to those above described. They are arranged in groups, 

 each group showing from four or five to twenty or more glands, in 

 each of which appear four or five very minute orifices (see figs. 1 and 

 2, v. s. ff.). Targioni-Tozzetti (p. 27) describes them as situated on 



