CHAPTER XII 

 INSECTS ON GREENHOUSE PLANTS 



MUCH has been published regarding insects which prey 

 on greenhouse plants, yet much remains to be learned of 

 their life history and the best methods for their exter- 

 mination. Prevention of attack, rather than attempting 

 to destroy established pests, is to be preferred. Cor- 

 rect environmental conditions stimulate a strong, vigorous 

 growth in plants, which is the first essential for keeping 

 in check attacks of insects. 



The yearly damage by insects in greenhouses is enor- 

 mous. In many cases it is due largely to a lack of knowl- 

 edge regarding the character of the attack and of methods 

 for combating it. As the plant-growing industry has in- 

 creased, resulting in frequent interchange of plants and 

 cuttings among growers in America and those of other 

 countries, there has been a corresponding increase in the 

 numbers and species of insects attacking cultivated plants. 

 To understand the best methods of combating insects, a 

 knowledge of their general character is necessary. Such 

 knowledge reveals the weak points in their reproduction, 

 growth and development, and suggests methods of ex- 

 termination. 



236. Structure. All insects in their adult or perfect 

 stage are characterized by having three pairs of legs, and 

 usually one or two pairs of wings. Their external skeleton 

 is variously segmented into joints or rings. They are 



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