34 iKebniary, 



In the Agricultural Gazette of New South Wales, September, 

 1892, p. 698, Mr. A. S. OllifE reports Asp. j^erniciosus in Australia on 

 pear. 



In September, 1894, I received from Mr. French, of Melbourne, 

 some twigs of peach trees thickly covered with a scale which, in my 

 paper on Coccidce (read November, 1894, published in Transac. New 

 Zealand Institute, vol. xxvii), I identified as belonging to the genus 

 Aonidia, and named Aon.fiisca. 



In March, 1895, the same gentleman sent me some apple twigs 

 with many scales, which I found to be Aspidiotus perniciosus. 



Finally, in July, 1895, Mr. Olliff sent me twigs of pear, peach 

 and apple from New South Wales, much infested by Aspidiotus 

 perniciosus. It was while examining these last specimens that the 

 characters which I observed in the adult females led me to compare 

 them closely with those of Aonidia fusca ; and as a result I cannot 

 help being considerably perplexed. 



The opinion which, for many years past, I have persistently ad- 

 vocated as regards the study of Coccidce is, that it is always better to 

 base distinctions, where possible, upon anatomical characters of the 

 insects themselves rather than upon external features of the coverings 

 (waxy or cottony or otherwise) under which they are sheltered. These 

 coverings may vary so much according to accidental circumstances that I 

 think they should be considered as of secondary, or even less importance. 

 In the case of the two insects of which I am now treating, I atn sorry 

 to say that I did not adhere strictly enough to my own rule. Size, 

 colour, form of the scale, food plant, and such-like things, have been 

 so greatly insisted upon, as I find, in all the accounts of Aspidiotus 

 perniciosus, that I have perhaps attached too much importance to 

 them ; and consequently it is possible that my identification of Aonidia 

 fusca is erroneous. 



All the authors who describe Asp. perniciosus give the following 

 characters of it : — 



1. — The scale is "grey;" the pellicles "yellow or reddish-yellow," "sometimes 

 black." 



2. — When on twigs, " the wood beneath the bark is stained red ;" " the cambium 

 layer of wood is stained purplish;" "the peculiar reddening effect on the 

 skin is a very characteristic feature ;" " the cambium layer frequently becomes 

 deep red or purplish ;" " if the twig be scraped with the finger-nail a 

 yellowish oily liquid will appear." 



3. — The diameter of the female puparium, or scale, is given by Comstock as about 

 ■j*3 inch ; I do not find it in other writers. 



