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Title: LARVAL REARING DENSITY EFFECTS ON LIPID RESERVES AND WING-LOADING IN FALL ARMYWORM ADULTS (LEPIDOPTERA: NOCTUIDAE)

Author
item Ferguson, Holly
item EATON, J. - GRADUATE SCHOOL
item Rogers, Charlie

Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: There is a need to learn more about why fall armyworm (FAW)moths migrate and the conditioning that prepares a FAW for migration. This, in turn, would aid in developing more effective area-wide pest management programs for this corn pest. Crowding, or density, which causes other insects to migrate, was studied in relation to certain migratory traits in the FAW. Two migratory traits that might be affected by crowding are fat content and wing-loading (body weight/wing area). A migratory moth needs large fat reserves and a low wing-loading, i.e., less weight in relation to its wing size, for enduring long distances in flight. Larvae were crowded at 3 levels: 1, 2, and 3 larvae/1 oz cup with ample diet and reared until adulthood. Wing widths and lengths were measured to obtain wing area estimates. Freeze-dried body weights were obtained, and fat extractions were accomplished on adults. Whole body fat content was significantly higher in moths from the highest density level (3 larvae/cup). However, wing-loading was not affected by crowding. Based on these results and results from other studies , crowding is not a significant factor on the migratory conditioning of the FAW. Weather, the crop plants, or both may be more important than density in affecting FAW migration.

Technical Abstract: A laboratory study was conducted to determine if a high larval rearing density produces premigrant traits in the fall armyworm, Spodoptera frugiperda (J. E. Smith), and if these traits can be used as criteria for separating non-premigrant from premigrant groups. The putative premigrant traits of high lipid reserves and low wing-loading were measured in newly merged adults of the fall armyworm. An increase in rearing density significantly increased adult whole body lipid content, but high lipid content was not related to high adult activity measured in previous studies. Although larval rearing density did not affect wing-loading, the armyworm as a migrant species showed lower than theoretically expected wing-loading. The lack of density-dependent increas lipid reserves associated with higher adult activity and the lack of density effects on developmental time and size (here and previous studies) may indicate that a premigrant phase induced by high larval density does not exist in the fall armyworm.