202 FOREST ENTOMOLOGY. 



afford several important advantages to the student. Thus where the 

 temperature is, comparatively speaking, perpetual summer, we find 

 several broods occurring throughout the year, as well as the creatures 

 in their various stages of metamorphosis. In the forest, on the con- 

 trary, many species are not only local in area but sparsely distributed, 

 and all are single-brooded. In hothouses, through importation, plants 

 are collected from various parts of the world, and thus, to some 

 extent, we get in private greenhouses and public botanical gardens 

 an approximate epitome of the scale -insects of the world. It is 

 therefore evident that, in order to understand the life -history of 

 many scales originally imported, but now acclimatised to our glass- 

 houses, recourse must be had to foreign and colonial literature. Not 

 only is it advisable to study the literature relative to foreign scales, 

 but it is essential to study the microscopical structure of the foreign 

 scales themselves which are to be found on our imported plants and 

 fruits. And as the dead females answer best for microscopical 

 examination, greengrocer's stalls may be looked upon as a very 

 happy hunting-ground more especially at a time of the year when 

 life is dormant, and when the working entomologist may use his 

 microscope as an instrument for original research in a comparatively 

 fresh field. 



But the study of foreign scales and the literature bearing on them 

 has, in addition to its charms and pleasures, a very practical bearing, 

 inasmuch as we find that some species are quite cosmopolitan in dis- 

 tribution. We also find that many species which are practically 

 identical to the naked eye, and likewise in point of damage, prove on 

 microscopical examination and in their life-history to be quite distinct. 

 As regards the value of such knowledge bearing on the discrimination 

 between foreign injurious scale-insects and the apparent introduction 

 of any particular injurious species into this country, as recognised 

 only from naked - eye characters practically identical to the casual 

 observer, one important case may be cited viz., the San Jose scale 

 (Aspidiotus perniciosus) from California, as compared with the 

 scurvy-bark louse {Aspidiotus ostreceformis) of this country. The 

 former is a sub-tropical insect, and would not likely withstand the 

 rigours of a "Western climate. In fact, it has not even established 

 itself under glass in this country. 



In the year 1898 it was thought the San Jose scale-insect had 

 established itself in this country, and so much was the scare felt 



