404 TachardiincB. 



may possibly represent the vestiges of anterior limbs, the insect 

 being otherwise completely apodous. 



The spiracles, during the development of the adult insect, so 

 completely alter their normal positions that the two pairs can do 

 no longer be described as anterior and posterior. The originally 

 anterior spiracles may even finally assume a position considerably 

 behind the true posterior pair (as in albizsicE and laced). They are 

 always more strongly developed than those of the other pair, and, 

 though originally situated on the venter, are gradually carried 

 round to the dorsum of the insect. The normally posterior 

 spiracles remain small and retain their original ventral position. 

 Under these conditions it is more convenient to describe the two 

 pairs of spiracles as dorsal and ventral respectively. 



Associated with the large dorsal spiracles are the stigmatic pro- 

 cesses. These organs have been described by some authors as 

 ' lac-tubes,' under the impression that they are principally concerned 

 in the secretion of the lac. As a matter of fact, they have an 

 exactly opposite function, namely — to prevent the accumulation of 

 the secretion at the particular spots where they are situated, and to 

 keep open the stigmatic orifices and permit the ingress of air to the 

 spiracles. This they effect by the secretion of waxy filaments from 

 special ceriferous pores which are grouped (usually in a denser 

 chitinous tract) on their apices. The processes may be approxi- 

 mately sessile — as in albizsicg,OY greatly elongated — as in conchiferata 

 and lacca. They are usually soft and fleshy, with a densely chitin- 

 ous tract (carrying the ceriferous pores) at the apex of each ; but, 

 in conchiferata, the processes are completely indurated, resembling 

 horns. In some species the stem of the process is so thin and 

 delicate that, under compression, it may be flattened down and 

 overlooked, when the denser apical tract will appear to be sessile. 



The dorsal spine is a character that is peculiar to the genus. 

 It occurs on the adult female of every species of Tachardia. One 

 species {aurantiacci) was originally described as being without this 

 peculiar organ ; but subsequent study has shown that it is present 

 on fresh examples of the insect, but has such a slender pedicel that 

 it is easily detached and lost. It is a conspicuous, stout, densely 

 chitinous spine, surmounted upon a fleshy tubercle or pedicel, and 

 is situated on the dorsum immediately above the base of the caudal 

 extension. The pedicel may be short and stout, or long and 

 slender. In the latter condition the spine is readily detached when 

 the specimens are dried, or during the process of preparation for 

 microscopical study. The spine is perforated by a central channel 



