. Control of the Mormon cricket by the use of poisoned bait. Grasshoppers. 4 CIRCULAR 5 7 5, U. S. DEPT. OF AGRICULTURE killed for each bait was then calculated by dividing the total number dead by the total caged. This system was used during the seasons of 1935 and 1936, but was discarded early in 1937 because the percent- ages killed from most of the baits were so nearly alike. Confinement of the crickets directly on the bait apparently resulted in their eating whatever was offered them with slight regard to the content of the m xture. In 1937 the system now in use was devised, and it was no
. Control of the Mormon cricket by the use of poisoned bait. Grasshoppers. 4 CIRCULAR 5 7 5, U. S. DEPT. OF AGRICULTURE killed for each bait was then calculated by dividing the total number dead by the total caged. This system was used during the seasons of 1935 and 1936, but was discarded early in 1937 because the percent- ages killed from most of the baits were so nearly alike. Confinement of the crickets directly on the bait apparently resulted in their eating whatever was offered them with slight regard to the content of the m xture. In 1937 the system now in use was devised, and it was not until then that marked differences in the efficiency of various baits became evident. This was called the "wing-pen" method. It consisted of a small pen about feet in diameter built of 10-inch galvanized iron with two 16-foot wings of the same material forming a V and set in front of and adjacent to it. The V was connected with the pen at its apex by a 4-foot removable chute. This chute consisted of a 1- by 6-inch pine board with 5-inch sides of galvanized iron nailed to the Figure 2.—Series of wings, chutes, and cages used in the wing-pen method as modified in 1939. The poisoned bait was spread in front of and within the V. The crickets were allowed from 20 minutes to 1 hour to feed and move into the pens of their own accord. If a sufficient number had not been captured at the end of 1 hour those within the V were driven up the chute and into the pen, where they were held for 4 days. As before, the dead crickets were removed each day and the remaining live ones counted on the fourth day. The final percentage of kill was calculated from the total dead and the total caged. The method was revised somewhat in 1939, when a small cage was substituted for the pen (fig. 2). The crickets were driven into the cage and then transferred to pens at a central location. In the wing-pen method the crickets were not forced to feed on the bait, as was the case in the f
Size: 2049px × 1220px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookpublisherwashingtondcusdeptofagriculture
