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Abstract. Rice Black Bug (RBB) is small and cryptic pest species that are believed to have caused significant yield loss of rice production in the Philippines. Various studies pointed to the variability in the ecology and morphology of populations of RBB. The present study reports on the variability in the wing venation pattern and shapes of the male and female genital plates structure in a non-outbreak population of RBB from Lala, Lanao del Norte. Results showed immense variability in wing venation patterns particularly in the type and number of marginal cells and the number and pattern of longitudinal veins. The marginal cells were either closed or open. On the other hand, the longitudinal veins were sometimes crossed, looped forming a closed circular pattern or at times show a complex criss-crossed pattern. Landmark-based geometric morphometric analyses of the shapes of the male and female genitalia showed variations in the length-width aspect ratio, concavity of the anterior margins and shapes of the posterior and anterior protrusions. The results may imply a high genetic diversity in this population of RBB despite present in a non-outbreak level. This diversity may have implications to the control and management of this rice insect pest.
Keywords: Genitalia, wings, phenotypic plasticity.
Introduction. Rice remains to be a primary staple food for Filipinos and this explains the fact that more than 2.3 million hectares of arable lands in the Philippines has been devoted to its cultivation (Barrion-Dupo et al 2007). However, rice production in the Philippines has its own share of problems as a significant amount of yield is lost to insect pests such as the rice black bug (RBB) (Scotinophara spp.) Barrion et al (2007) described species of RBB that are known to attack rice plants in all of its growth stages. Increase in RBB densities in farm lands in the country have been reported by Redondo et al (2007). However, an important observation is that RBB is irregularly distributed in the Philippine archipelago and show abundance in only some areas (Demayo et al 2007).
The state of RBB taxonomy in the Philippines has been particularly confusing due to the fact that populations of this insect pest show immense variability in both reproductive and non-reproductive traits (Barrion et al 2007). There are...