24 PARASITES OF THE COTTON BOLL WEEVIL. 



The first type was a cubic cage made very easily by using strips of 

 cork for the framework and fine meshed wire (known as 50 to the 

 inch, but really 35 and 45 to the inch) for the sides. One side was 

 fixed with two openings which were closed on the inside by a tin 

 shutter. The lower opening was round, and in this a cork with a 

 glass tube through it was placed before the shutter was raised. 

 Thus the parasites, being attracted to light, could be quickly removed 

 by darkening the sides and allowing the light to enter only through 

 the tube. When the shutter was raised higher it exposed a larger 

 opening through which material could be passed. 



With this first cage as a type various modifications were contrived, 

 all with wire fronts, shutters of various kinds, and corked holes for 

 the admission of a tube or for passing in small objects. Cigar boxes 

 became the bases for these cages. 



Still another modification was a wire cylinder corked at one end 

 and with a smaller cork centered in this for the removal of material. 

 The other end was covered with cheese cloth. 



It was found impossible to provide plant conditions in a small 

 cage unless the plant were actually transplanted or grown from 

 seed. A branch of cotton withers so quickly that experiments of 

 this sort were of no value. 



Both kinds of tubes were tested on the plants, but the mica tube 

 caused a heavy sweat and killed the branch it was on; the wire tube 

 was too heavy. All of the plants placed under the large parasite- 

 tight cages with glass sides died before results could be expected. 



2. FIELD WORK RELEASE OF PARASITES. 



The release of parasites in the field was not commenced until 

 September 12 on account of the small amount of material gathered 

 prior to that date. Notwithstanding that fact the results give an 

 indication of success. On the laboratory farm at the top of the hill 

 there were released 35 parasites on September 12 and 38 on Septem- 

 ber 15. These parasites were of three species. An examination of 

 hanging forms was made in this part of the field and another down 

 the hill at the opposite side and about 350 yards distant. At this 

 time the check area ("B," fig. 5) showed 1.9 per cent higher para- 

 sitism than the parasite area ("A," fig. 5). Twenty days later, on 

 October 2, like examinations were made with the result that the 

 percentages were reversed; "A" showed an increase of 2.6 per cent 

 and U B" showed a decrease of 6.5 per cent; that is, "A" was 7.2 

 per cent more highly parasitized than "B" and showed a real gain 

 in parasitism of 9.1 per cent. On October 6 this examination was 

 followed by another, and, although the difference was less, "A" was 

 3.9 per cent more highly parasitized than "B." Plat "A" was next 

 to a fence and separated from another field of cotton by a road and a 



