Forewing Shape Variability Between Sexes and Across Populations of the Rice Bug, Leptocorisa varicornis Fabricius (1803) Using Geometric Morphometrics

Abstract

Leptocorisa varicornis (F.) (1803) rice bug is a serious pest of rice. Misidentification of this pest had led to non-effective management strategies resulting to possible emergence of insecticide resistance. Proper identification of this species is necessary in developing effective management strategies against this pest, and correct identification needs accurate examination of the insect's morphology. Geometric morphometrics (GM) statistically analyzes shape variability allowing better understanding of the nature and variability of the insect in relation to the evolvability of characters and its possible implications to adaptability of the organism. This study made use of GM to determine forewing shape variability between sexes and across populations of L. varicornis (F.) from selected localities in Northern Mindanao, Philippines. Exploratory results initially showed that variations between sexes were generally characterized by differences in overall shape of forewing, apex and wing base. Variations across populations were associated largely with differences in overall forewing shape, contour of inner margin, and shape of wing base. Series of confirmatory tests obtained highly significant results, which all confirmed presence of intersexual and interpopulation variations in L. varicornis. Environmental stressors like seasonal cropping, flood and application of pesticides might influence differences in forewings of rice bugs since rice bugs have to fly to long distance after cropping or change location when existing habitat conditions are no longer suitable for their survival. Thorough understanding of the biological basis of the observed variations is essential for the effective control against this species.