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CHAPTER VI. 



COCCID^E (Scale-Insects). 



There is perhaps no class of insects more puzzling to the practical 

 husbandman, the economic entomologist, or the biologist who is 

 anxious to gain a general knowledge of insect structure and life- 

 histories, than the Coccidse or Scale-Insects. The student must rely 

 almost entirely upon the microscope for the accurate determination of 

 these insects, which from their minute size present exceptional diffi- 

 culties. Even for general field-work it is necessary to have recourse to a 

 strong pocket-lens ; as to the naked eye, they may be confounded with 

 lenticels as, for example, those on birch-twigs. They may also be 

 mistaken for certain micro-fungi on leaves or stems of various plants. 



In the Introduction it was emphatically asserted that concentration 

 in the study of forest entomology was indispensable, inasmuch as 

 almost every natural order was represented, and thus as a branch 

 of forest science, to the forester in particular, general versatility in 

 entomology was impossible. Scale - insects, however, are to some 

 extent an exception to this rule. The arboreal-feeding species of 

 this important family are comparatively few, and therefore, in order 

 to thoroughly understand the salient characteristics, it is necessary to 

 glean information from all available sources. In other words, in order 

 to thoroughly understand the special part, it is essential to make a 

 general study of the available whole. 



But though the arboreal species in this country are comparatively 

 few in numbers, the forester, or student of forest entomology, can 

 always obtain an abundance of material from various plants cultivated 

 under glass the amateur greenhouse often being a happy hunting- 

 ground. 



Temperature and climatic conditions are important factors in the 

 distribution and regulation of scale-insects. Hence warm greenhouses 



