30 Transactions. — Zoolocjy, 



colour and in the form of the antennas ; also A. multispinus, mihi, in some 



particulars, but wants the large and numerous conical spines of that species, 



and is also a good deal larger, and the sac is whiter. 



Genus Dactylopius, Costa. 



1. Dactylopins glaucus, mihi. 



(Trans., vol. xi., p. 219.) 



The male of this species undergoes its last metamorphosis in a narrow 

 cylindrical sac of pure white cotton, about J inch in length, and open at 

 the end. Sometimes twenty or more of these sacs may be seen on a leaf, 

 with the females and young crawling about amongst them. 



The male insect is about -^ inch long, brown in colour, and when newly 

 hatched covered with white meal. Form normal ; the body is rather thick, 

 the anal spike very short. Antenna? of ten joints, hairy ; the last eight 

 joints equal to each other. Feet slender, hairy ; the upper digitules long 

 fine hairs, lower pair very short. The seta of the haltere is short. Wings 

 rather large. 



G-enus Icerya, Signoret. 



1. Icerya purchasi, mihi. 



(Trans., vol. xi., p. 221.) 



In the fourteenth annual report of the Colonial Botanical Garden, 1883, 

 p. 20, I find it stated that this insect perhaps derives the differences which 

 it exhibits when compared with the Mauritian I. sacchari, from change of 

 food or climate. The natural food of Icerya in Mauritius is the sugar-cane ; 

 it was first found in New Zealand on Acacia : and it is suggested that the 

 "violent change " from " sweet juice to tannic acid " might account for 

 some change of form. This statement appears to me to rest on a mis- 

 apprehension. As pointed out in my paper of 1883 (Trans., vol. xvL, 

 p. 140), Icerya purchasi possesses organs and performs operations which are 

 not observed in I. sacchari. Whatever modifications might, after lapse of 

 ages, be produced by change of food or climate, it is scarcely likely that in 

 a year or two they would include the elaboration of special spinning organs 

 and the power of constructing a peculiar and complicated ovisac. I am 

 aware that nobody has yet settled the vexed question of the true basis and 

 limits for differentiation of species ; but surely the absence or presence of 

 important organs and a marked difference in the mode of propagation may 

 be taken, at present, as sufficient for the purpose. 



The number of New Zealand scale insects might be indefinitely extended 

 if mere colour, or minute features referrible to varying food or other con- 

 ditions, were taken to constitute new species ; and I have carefully avoided 

 taking them as such. Yet, perhaps we might also fall into error and con* 

 fusion by attempting too much in the other direction, 



