NAPHTHALENE AS A GREENHOUSE FUMIGANT 7 



The age or degree of incubation of the eggs influences their susceptibility 

 to fumigation, as shown in Table 2. In this experiment, eggs were divided 

 into two groups: those which had become a deep straw color and showed 

 the developing embryo within, and those which had been laid during the 

 previous 24 hours. These eggs were placed in short glass tubes filled with 

 plaster of Paris, which permitted a small amount of moisture to reach them 

 when the tubes were set on damp sand (14). Since more than 80 percent of 

 the unfumigated eggs hatched, these tubes apparently provided satisfactory 

 conditions for incubation. Under these conditions, none of the older eggs 

 hatched after one or more fumigations, while it required four fumigations to 

 prevent all of the newly laid eggs from hatching. Fumigated eggs developed 

 a slightly darker color than the untreated eggs, but this change in color was 

 not always consistent and in many cases it was impossible to determine the 

 effect of the treatment until long after the eggs should have hatched under 

 natural conditions. 



Table 2. — Mortality of New and Old Eggs of Red Spider after 

 Fumigation with Naphthalene. 



Dosage 3 ounces per 1,000 cubic feet. 



Temperature 80°F. Relative Humidity 90 percent. E-iposure 6 hours. 



Waltham, Massachusetts. March 1930. 



On Active Stages of Red Spider 



An examination of infested plants after fumigation which has resulted in an 

 incomplete kill of common red spiders usually shows a predominance of larvae, 

 second stage nymphs (deutonymphs) , and adult males among the living spiders. 

 The results summarized in Table 3 indicate that these forms have a slightly 

 greater resistance to naphthalene fumigation than the first stage nymphs 



