RED SPIDER. 193 



a large measure on warmth and other surround- 

 ings. When newly hatched the spiders are very 

 light in color. In fact, it is difficult to distinguish 

 them from the masses of web and the yellowish 

 portions of the affected leaf. As the spiders 

 grow older they molt several times, and finally 

 attain full size, when their color is more or less 

 yellowish red. The color, however, varies greatly 

 and it is seldom that any lot on two different 

 plants are found to be exactly alike. 



The mites are exceedingly difficult to kill and 

 for this reason great care must be exercised in 

 not allowing them to attain sufficient numbers to 

 seriously check the growth of the plants before 

 putting forth efforts to destroy them. It is the 

 general belief among florists that spiders do not 

 thrive in moist air, but this does not seem to be 

 the case, for if proper conditions are present moist 

 air alone is not sufficient to hold them in check. 



Tobacco, either in the form of smoke or ap- 

 plied in other ways, has little effect upon the 

 mites themselves and probably does not injure 

 the eggs in the least. Fumigation, therefore, is 

 useless in this connection. What is true of 

 tobacco will also hold good with other poisonous 

 gases, such as cyanide gas, which is now coming 

 into general use for greenhouse work. When we 

 first commenced using the cyanide gas we were 

 hopeful that it would prove valuable in destroying 

 spider. It is true that spiders subjected to the 



