The Suppression of Isolated Populations of Sphingids1 by Blacklight Traps

Abstract

When blacklight traps were operated at a density of 3/mile2 for 43 months on St. Croix, U. S. Virgin Islands, the collections of sphingid moths were found to be associated with the seasonal pattern of rainfall. The 12-month collection of Hyles lineata (F.) was 17.5% of the 1st 12 months collection after 43 months. The collcction of Callionima ramsdeni (Clark) had dropped 50% after 33 months of trapping but increased to 64% of the 1st 12 months after 43 months. The collection of Agrius cingulatus (F.) was 32% that of the 1st year after 36 months but increased to 81% after 43 months. The collection of Manduca rustica harterti (Rothschild) was 14% that of the base year after 39 months but increased to 21% after 43 months. The collection of Eumorpha vitis (L.) was 15% that of the base year after 39 months but increased to 19% after 43 months. The collection of Xylophanes pluto (F.) was 36% that of the initial year after 36 months but increased to 70% after 43 months. The collection of Xylophanes tersa (L.) was 59% that of the base year after 37 months but increased to 80% after 43 months. The increased collections the last year of trapping were attributed to the absence of a dry season that year. If the collection trends prior to that unusual rainfall pattern had continued, several species would have been eradicated by an additional year of trapping pressure.