260 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



Effect of Food. — During the summer the parasites were fed on 

 numerous substances, such as sweetened water, plain water, dew on 

 corn plants, sap from corn stalks and gummy secretions from sun- 

 flowers. In all cases the parasites fed readily, but, with the exception 

 of sweetened water, the effect of feeding was not appreciable in the 

 length of life or in oviposition. Sweetened water prolonged life from 

 a few days to several weeks and the parasites showed a greater activity 

 in oviposition. 



Table 4 gives the effect on the length of life of the adults at differ- . 

 ent seasons of the year when fed sweetened and plain water, and when 

 not fed. 



Table 4. Showing Effect of Food on Length of Life 





Sweetened Water 



Plain Water 



No Food 



Date 

















No. Parasites 



Length of 



No. Parasites 



Length of 



No. Parasites 



Length of 





Life 





Life. 





Life 







Days 





Days 





Days 



June 



17 



16.5 







6 



4.0 



7-16 to 8-1 



120 



7.0 



3 



3.6 



86 



3.3 



8-7 to 8-17 



127 



10.3 



48 



3.0 



138 



3.9 



9-4 to 9-17 



96 



9.6 



35 



9.2 



71 



9.5 



9-24 to 10-17 



14 



26.2 



9 



18.0 



33 



15.5 



Effect of Light and Contact. — ^The adult parasites show negative 

 phototropism. In the vials they alwaj^s crawled in between the cotton 

 and the glass on the underside where it was darkest. If a paper label 

 were placed in the vial the parasites would get on the under surface. 

 When placed in a dark box which had a glass tube inserted for emer- 

 gence to light the parasites seldom appeared in the tube. 



The adults also show a positive thigmotropism and whenever pos- 

 sible they endeavored to crawl in between two closely fitting objects. 

 In the vials they were found wedged in between the vial and the cotton 

 plug and in the field they were often found between the leaf sheath 

 and stalk of plants or in small cracks in the ground. 



The two reactions are necessarj^ in the life economy of the insect 

 in its search for chinch bug eggs. 



A Member: I would like to ask as to whether this parasite has 

 transferred its habitat to the chinch bug or whether it has been present 

 all the time in small numbers? 



Mr. J. W. McColloch: Indications are that it has been present 

 for some time. The percentage of parasitism the first year we found 



