Cuticular hydrocarbons on elytra of the Diaprepes root weevil Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae) Stephen L. Lapointe, Wayne B. Hunter and Rocco T. Alessandro USDA-ARS, U.S. Horticultural Research Laboratory, 2001 South Rock Road, Ft. Pierce, FL 34945, USA Abstract 1 External gland openings and associated structures on the elytra of teneral and mature Diaprepes root weevils, Diaprepes abbreviatus (L.), were elucidated by scanning electron microscopy (SEM). 2 There were clear differences between teneral, callow adults and fully mature adults. In the field, teneral adults remain in the pupal chamber in the soil until sclerotization of the cuticle is complete or nearly so. 3 Phenotypic variation of the elytra in this species consists of varying patterns and coloration of scaled intervals between a variable number of raised ridges devoid of scales. In addition to being thinner and lighter in colour than fully mature adults, the elytra of teneral adults were devoid of waxy hydrocarbon secretions. 4 External gland openings at the base of each scale were observed on teneral elytra and mature elytra washed with methylene chloride. 5 SEM evidence to document the production of waxy filaments by these glands and partial characterization of these by gas chromatography and mass spectro- metry are presented. Keywords Citrus, Diaprepes abbreviatus, hydrocarbons, Insecta, wax glands. Introduction Insects secrete a complex mixture of lipids including wax esters, triglycerides, hydrocarbons and other compounds commonly referred to as wax (Waku & Foldi, 1984). The structures associated with production of these compounds range from simple pore canals that produce the epicuticle’s outer wax monolayer, to highly modified cuticular struc- tures that give shape and structure to extruded wax, as seen most notably in species of aphids, mealybugs, whiteflies and larvae of lepidopterans and coccinellids (Pope, 1985; Nelson et al., 2000). The Diaprepes root weevil, Diaprepes abbreviatus (L.), is a major constraint to production of citrus and ornamentals in Florida and the Caribbean. Since the discovery of this pest in Florida (Woodruff, 1964), it has spread throughout peninsular Florida. Larvae of this species are a primary concern of Florida citrus producers because of the destruc- tive habits of D. abbreviatus, and the difficulty of detecting and monitoring soil-inhabiting larvae in general. Larvae and adults are highly polyphagous, feeding on the roots and leaves, respectively, of many wild and cultivated plant species (Simpson et al., 1996). Larvae pupate in the soil. When adults emerge from the pupal exuvium, the callow adults remain in the pupal chamber during a teneral period of several days or perhaps weeks until sclerotization of the cuticle is complete (Wolcott, 1936). Wolcott (1936) observed that oviposition commenced at 3–7 days after emergence from the soil and an unknown period in the pupal chamber. Adults are long-lived and oviposition occurs over a prolonged period, probably months. A trap based on an attractant would be a useful tool for monitoring adult populations and timing management practices for D. abbreviatus. Although anecdotal observa- tions indicate that adults aggregate on particular citrus trees in the field, volatile aggregation or mating pheromones have not been identified for this species despite considerable effort. Some insect sex pheromones are similar to hydro- carbons found on insect cuticle (Jurenka & Subchev, 2000). In the German cockroach, for example, Gu et al. (1995) showed that hydrocarbon and methyl ketone sex pheromone are synthesized by integumentary tissue, probably oenocytes, and either delivered to the associated epicuticle or transported by lipophorin in the haemolymph Correspondence: Stephen L. Lapointe. Tel.: þ1 772 462 5914; fax: þ1 772 462 5986; e-mail: slapointe@ushrl.ars.usda.gov Agricultural and Forest Entomology (2004) 6, 251–257 # 2004 The Royal Entomological Society