European wood weevil Pentarthrum huttoni Fig 57c

Adults are 2.5-5.0 mm long, blackish brown to reddish brown. The snout length is about two-thirds the length of the pronotum; antennae are nine-segmented. Full-grown larvae are about 3.5 mm long and 1 mm wide; they are legless, strongly convex, and covered with fine spines and setae. Exit holes in the wood surface are irregular in shape and 1.5-2 mm diameter. Eggs are laid about 4 days after mating. Eggs are deposited singly in cracks and crevices, or in holes excavated by the female, which are sealed with a white substance from the ovipositor. Egg-laying continues for about 3 months; fecundity is 20-30 eggs. Hatching is in about 16 days, and the first-stage larvae use egg-bursters on the sides of the first three abdominal segments. Larval development includes five instars and lasts 6-8 months. Larvae tunnel parallel to the wood surface, but meandering tunnels are common. Larvae are capable of digesting cellulose and hemicellulose, but lignin is excreted in the frass. The full-grown larva constructs a pupal chamber, which may be lined with fungal hyphae; the pupal period is about 16 days. The adult beetle cuts an exit hole to the wood surface. Dead adults are frequently found atwindows or around lights. This species is distributed in northern USA, Canada, and Europe.

Pine weevils, pine borers, sipalinus spp. Adults are 14-20 mm long and brown to brownish black. The head and thorax are covered with tubercles and the femora are enlarged. These beetles infest pine (Pinus spp.) wood used in packing cases or structural wood. Larval development takes 1-3 months and adult beetles emerge from infested wood in use. These beetles are found throughout Europe and Asia.

Granary weevil, sitophilus granarius (Fig. 5.7d) Adults are 2.5-4.5 mm long, dark brown to blackish brown, and without pale markings on the elytra. Pronotum has punctures that are distinctly elongate or oval and not round or irregular-shaped, as in S. oryzae and S. zeamais. Wings are greatly reduced or absent under the wing covers, and the adults do not fly. The male snout is shorter, wider, and has more punctures on the dorsal surface than is the case in the female. Full-grown larvae are 3.5-4.0 mm long, yellowish white, and with a dark brown head.

Eggs are deposited in a hole chewed into the grain kernel and a gelatinous material is deposited to seal the hole over the egg; fecundity is 36-254 eggs. Females deposit about 43 eggs at 17 °C, 100 eggs at 21 °C, and 268 at 25 °C; oviposition ceases at about 9.5 °C. Females do not oviposit on grain too small for complete development of a single larva. Larval development takes 57-71 days on wheat at 21 °C, and about 45 days at25 °C and 75% RH. Larvae tunnel in the seed and pass through four instars; the lastinstar forms a pupal cell inside the grain kernel; the pupal period is 5-16 days. Females live for about 170 days. The adults and larvae of this weevil will feed on grain and cereal products, but it is primarily a pest of whole grain. It breeds in chickpeas, and all common grains such as maize, oats, barley, rye, wheat, kafir, buckwheat, and millet. S. granarius tolerates temperatures as low as 11 °C, and is well established in temperate regions of the world, and in cool upland regions of the tropics. This species is not usually a household pest because it infests whole grain.

Rice weevil, sitophilus oryza (Fig. 5.7f, g) Adults are 3.04.6 mm long, reddish brown to blackish brown; elytra are marked with four reddish to yellowish brown spots. Wings are fully developed. The pronotum has punctures which are nearly circular or slightly elongate, less than twice as long as wide. It is closely related to S. granarius, but is distinguished by the circular punctures on the pronotum. The distribution of S. oryza and S. zeamais coincide, and they are difficult to separate. Full-grown larvae are about 4 mm long, yellowish white, and C-shaped. Eggs are laid singly in grain kernels after the female bites a small hole in the surface of the grain kernel; the hole is sealed with a waxy secretion; fecundity is 150-400 eggs. Hatching is in about 6 days at25 °C and success is about 75%. Oviposition occurs between 15 and 30 °C. Highest oviposition is usually 1-2 weeks after emergence, then declines until the female dies in about 3 months. At a density of one weevil per 50 kernels of wheat, oviposition is maximal at 344-384 eggs per female at 25.5-29.1 °C and 14-20% moisture. No eggs are laid on grain with moisture content below 10%. Larval development is through four instars and takes about 26 days at32 °C, 25 days at 29 °C, and 94 days at 18 °C and 70%. The pupal period lasts about 5 days, and adults remain in the pupal chamber for about 5 days before emerging. Temperature limits for development on wheat with moisture content of 14% are 15.2 °C and 34 °C. Adults live 4-5 months.

This species is nearly cosmopolitan in warm and cool temperate regions of the world. Itfeeds on beans, nuts, cereals, and cereal products such as macaroni and cake flour, rice, wheat products, and even fruits such as grape, apples, and pears. Direct damage is caused to cereal grain by one or more (maize) larvae feeding inside the grain. Adults can fly up to 1 km to infest stored grain or ripening fields of grain.

Maize weevil, sitophilus zeamais (Fig. 5.7h, i) Adults are about 4 mm long and dark brown; the prothorax has round punctures. This species is closely related to S. oryzae and S. granarius. It is difficult to separate from S. oryzae, but is distinguished from S. granarius by the round punctures on the prothorax; these are oval in S. granarius. Eggs are deposited in the grain kernel; hatching is in about 6 days. Larval development on English wheat at 70% RH is 40 days at 25 °C, and 110 days at 18 °C; development is 35 days on hard red winter wheat at 27 °C and 69% RH. Natural mortality of first-stage larvae ranges from 3.5% at 80% RH to 30% at 50% RH. It is a common pest of grain crops in tropical regions around the world. Adults fly from granaries to fields to start infestations that continue in storage.

Black wood weevil, Tomolips quercicola Adults are about 3 mm long, cylindrical, and shiny black. The snout is slightly longer than the head, robust, and not curved; antennae are nine-segmented. This species occurs in eastern USA, west to Oklahoma and Texas, and also in Guatemala.

Other Curculionidae There may be local populations of weevils that peak at certain times and result in adults moving to other habitats. Some are attracted to lights at night, others simply move away from infested areas and encounter buildings. The acorn weevil, Balanimus uniformis, occasionally enters houses in California. Trachyphloeus bifoveolatus has been recorded in houses in eastern and western USA. Pea weevils, Sitona lineata, occur in large numbers in and around houses in August and September when the adult weevils leave fields and seek places for hibernation sites. Weevils reported infesting moisture-damaged and decayed structural wood include Euophryum rufum, Pentarthrum huttoni, P. australe, and Caulotrupodes aeneopiceus. Species of Rhyncolus are usually found under bark or associated with other weevils that feed under bark; R. brunneus occurs as infestations in structural softwood previously infested by Hemicoelus gibbicollis. Larvae and adults are found in the surface layers of infested wood; the frass is round, shiny, and yellowish brown.

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