504 Appendix. 



upon climatic barriers in regard to the Coccidse. As Mr. Cockerell * says : 

 " it is probable that the very rapid reproduction of Coccidae enables them 

 to quickly adapt themselves to changes of climate, through survival of the 

 fittest. Thus if there are a million scales in an orchard which is touched 

 with frost, if only one gravid female survives it will suffice to eventually 

 re-stock the orchard and with a comparatively frost-proof race." This 

 authority gives as an example the Peach Scale (Diaspis ami/gdaU), which 

 flourishes equally in Washington and in the tropics. We must remember 

 we have found the last-named breeding here. Moreover, the scale insects 

 are so erratic in their behaviour in any new country into which they are 

 introduced that it is quite impossible to predict the results of their 

 introduction. 



Although it is extremely unlikely that we shall sufiier from its intro- 

 duction, it is nevertheless advisable, when we take into consideration the 

 peculiar circumstances of the case, that all fruit-growers and gardeners 

 should be able to detect this scale, of which Professor Webster says : — 

 " Of all scale insects at present known in America, this is the most to be 

 feared on account of its deadly effects on the trees, the rapidity with 

 which it increases, and the difficulty of killing it." One of our chief 

 authorities on scale insects in this country, Mr. Newstead, said at a 

 meeting of the Entomological Society of London, that there is no reason 

 to suppose that it would be more injurious in this country than the 

 Mussel Scale (M. pomorum), since in this country it would probably 

 conform with the habits of all other scale insects and become single 

 brooded. But in orchai'ds we find the Mussel Scale often most injurious 

 to apple trees, especially young stocks. We must not overlook the fact 

 that it has also occurred in Germany. 



Other Scales Might be Mistaken for A. perniciosiis. 



It is extremely difficult to identify the San Jose scale from amongst 

 the other thirty odd species of the genus Aspidiotus, when the scales are 

 detached. But when present on the fruit and bai-k they can easily be 

 told by an expert by the changes produced on the plant tissues around 

 and beneath the scales and by their microscopic structure. 



A common scale met with in greenhouses is A. nerii, the Oleander or 

 White Scale — its snowy whiteness will distinguish it from A. perniciosus. 

 The common Camellia Scale [A. camellise) is similar in form but yellow 

 when fresh, and on tearing away the upper scale a pui-e white under-scale 

 is seen closely adhering to the under surface. In all cases an expert's 

 advice should be sought before we imagine we have A. perniciosus, and we 

 are sure that great authority, Mr. Newstead, of the School of Tropical 

 Medicine at Liverpool University, would gladly help any grower in 

 settling the question. 



* ' On the Danger to American Horticulture from the Introduction of 

 Injurious Insects,' New Mexico (1897). 



