Age-related changes in the chemical composition of female pheromone gland of the Egyptian cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae)

Abstract

Do h a H e s h a m E l -Ga s h i n g y El-S a e i d A h me d N a i e m M e r v a t Ra f e i k A b o u S e a d a A m a l I b r a h i m S e i fAge-related changes in the chemical composition of female pheromone glands of the Egyptian cotton leafw orm, Spodoptera littoralis (Lepidoptera: Noctuidae) ABSTRACT:The Egyptian cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae) is a serious pest that attacks a wide range of crops in Egypt. To relate the age with the chemical composition of the pheromone glands of the female S. littoralis, the chemical components of the glands were analyzed using gas chromatography coupled to mass spectrometry (GC -MS). The pheromone glands of the females were excised at four different ages: newly emerged (D 0 v), one-dayold (D1v), two-day-old (D2v), three-day-old (D3v) and three-day-old mated females (D3m). The pheromone glands contained 54 compounds in the hexane extract, (1 ketone, 1 acetate, 2 fatty acids, 3 esters, 6 aldehydes, 12 alcohols and 29 hydrocarbons). The presence and relative amounts of th ese compounds in the gland varied with age. Few compounds were observed in the glands of D0v, increased in D1v, D2v, and D3v, and remained almost constant in D 3 m. Fifteen compounds were previously identified as sex pheromone components in other Lepidoptera ; the major compounds were the two hydrocarbons, hentriacontane and heptacosane. Another fifteen components were previously identified from different insect orders other than Lepidoptera. The other twenty-four compounds were identified for the first time in insects. Determination and identification the sex pheromones of S. littoralis may present safe biologically active compounds that could be used in the management programs for this pest in Egypt. KEY WORDS:Spodoptera littoralis, Pheromone glands, Gas chromatography and Lepidoptera CORRESPONDENCE:Do h a H e s h a m E l -Ga s h i n g y Entomology Section, Zoology Department, Faculty of Science, Tanta University, Egypt INTRODUCTION:In the last four decades, there have been extensive researches on insect semiochemicals "The Pherobaseˮ (El-Sayed, 2014).They are chemical compounds implicated in the transfer of information from one individual to another to trigger a behavioral and physiological response in one or both insects (Dicke and Sabelis, 1988 and W olf, 1988; Ando et al., 2004). In Lepidoptera these compounds "The Pherobaseˮ (El-Sayed, 2014) play different roles.Virgin Lepidoptera females emit sex pheromones which cause attraction of males to the location of the female and subsequently, mating takes place (Kingan et al., 1993).In moths pheromone communication signals, both quantitative and qualitative intraspecific differences have been found across geographic regions (Klun, 1975;Roelofs et al., 1985). Such variation has generally been hypothesized to be due to selection and genetic control of these differences (Vogel et al., 2010). The composition of the female pheromone glands S. littoralis is highly dependent on the origin of the strain and its geographical distri...