Biology and Morphometric Analysis of Rice Weevil, Sitophilus oryzae (L.) with Emphasis on Larval Growth Patterns
Mohd Yahya
Department of Entomology, College of Agriculture, Acharya Narendra Deva University of Agriculture and Technology, Ayodhya 224229 Uttar Pradesh, India.
Sameer Kumar Singh *
Department of Entomology, College of Agriculture, Acharya Narendra Deva University of Agriculture and Technology, Ayodhya 224229 Uttar Pradesh, India.
Kamal Ravi Sharma
Department of Entomology, College of Agriculture, Acharya Narendra Deva University of Agriculture and Technology, Ayodhya 224229 Uttar Pradesh, India.
Umesh Chandra
Department of Entomology, College of Agriculture, Acharya Narendra Deva University of Agriculture and Technology, Ayodhya 224229 Uttar Pradesh, India.
Priyanshi Kamal
Department of Entomology, College of Agriculture, Acharya Narendra Deva University of Agriculture and Technology, Ayodhya 224229 Uttar Pradesh, India.
Ankit Kumar
Department of Entomology, College of Agriculture, Acharya Narendra Deva University of Agriculture and Technology, Ayodhya 224229 Uttar Pradesh, India.
Ram Veer
Department of Entomology, College of Agriculture, Acharya Narendra Deva University of Agriculture and Technology, Ayodhya 224229 Uttar Pradesh, India.
*Author to whom correspondence should be addressed.
Abstract
A laboratory investigation was conducted to study the biology and morphometric development of the rice weevil, Sitophilus oryzae (L.), on rice grains under controlled conditions. The insect culture was maintained at 27 ± 1°C and 70 ± 5% relative humidity, and observations were recorded on developmental duration, reproductive parameters and stage-wise morphometry. The incubation period ranged from 5 to 8 days. Four larval instars were observed, with durations of 3–6, 4–7, 6–8 and 7–9 days, respectively, and the total larval period ranged from 23 to 28 days. The pupal period varied from 6 to 9 days. Adult longevity ranged from 56 to 67 days in males and from 70 to 82 days in females, while the total life cycle varied from 90 to 99 days in males and from 105 to 123 days in females. Females laid 186–218 eggs, with an oviposition period of 45–55 days and egg hatchability of 79.57–84.06%. Morphometric measurements showed a progressive increase in body size during development. Egg length and width were 0.36 ± 0.01 mm and 0.16 ± 0.02 mm, respectively. Larval length increased from 0.51 ± 0.04 mm in the first instar to 2.02 ± 0.20 mm in the fourth instar, while larval width increased from 0.35 ± 0.04 mm to 1.52 ± 0.05 mm. Head capsule width increased from 0.19 ± 0.01 mm to 0.46 ± 0.01 mm, with growth ratios of 1.35, 1.34 and 1.33 between successive instars. Strong positive correlations among instar number, larval dimensions and head capsule width indicated that head capsule width is a useful character for distinguishing larval instars and assessing larval growth patterns.
Keywords: Stored-product insect, head capsule width, instar determination, oviposition, Dyar’s law