34 



INSECT ENEMIES OF THE BOLL WEEVIL. 



numbers on the plants and many immature stages were developing 

 in green squares and bolls. 



Table XVIII gives the results of the examinations made immedi- 

 ately after the freeze. 



Table XVIII. — Mortality of the boll weevil in Texas, November, 1907. 



1 Several. 



2 Most of the death from "other causes" in bolls was due to proliferation, which seems to be stimulated 

 by frosts. 



From this small number of stages no general statement can be made. 

 Of the 394 stages 55.3 per cent were killed by cold. Of the stages 

 in green squares or bolls, 98 per cent were killed by the cold. 



The most interesting point is that although 98 out of 100 weevil 

 stages in green forms were killed, a parasite larva was found to have 

 just hatched from its egg on a weevil larva killed by cold. Three 

 other similar cases were found in dry forms. Seventeen cases of 

 parasitism were found on the 394 stages. Among these were two 

 living eggs of which one was an entirely new type and also two pupse 

 which proved to be Hahrocytus piercei. 



The remainder of the winter of 1907-8 — that is, from December to 

 March 1 — had a mean temperature a few degrees above the normal, 

 but with several severe cold spells. During the four winter months 

 the precipitation m both States was above the normal. The short 

 cold spells with warmer intervening weather and heavier rainfall 

 were disastrous to the boll weevil. The February examination to 

 ascertain the mortality of the weevil indicated about 98 per cent 

 mortality. As a result of the extreme scarcity of weevils in the spring 

 and summer m most parts of Texas, there was a great reduction in 

 the number of parasites. In fact, in the northern portion of the 

 Texas black prairie the parasites were forced to seek other hosts. A 

 killing freeze in November, 1908, again killed many boll weevils. 



