06/11/2011 Towards integrated commodity ... - Se… Home "" """"> ar .cn .de .en .es .fr .id .it .ph .po .ru .sw Continued Contents - Previous - Next 8. SILVANIDAE The Silvanidae are a small family closely related to the Cucujidae. The adults are narrow and distinctly flattened, possess 11 -segmented antennae with a compact club. The elytra completely cover the abdomen, and there are five visible abdominal sternites. The tarsi are all 5-segmented. Most species are probably predacious, but two species of Oryzaephilus are of great importance as secondary pests attacking broken or milled cereals and oilseeds, while Ahasverus advena Waltl, the "foreign grain beetle", probably feeds on moults and refuse, and is rarely found in grain which is in good dry condition. Another closely related species, Cathartus quadricollis (Guerin-Meneville) which resembles the saw-toothed grain beetle, but differs by the square prothorax which lacks the six large teeth on either side, is one of the most common beetles in stored corn in the Southern USA, and on damaged and exposed ears in the field. Its form and habit are also similar, while the larvae have the annoying habit of devouring the germs of the seeds in which they breed. (i) Oryzaephilus surinamensis (L.), The saw toothed grain beetle. Small (2.5-3 mm) brown beetle; distinguished by serrated lateral margins of thorax. D:/cd3wddvd/NoExe/…/meister11.htm 1/248 06/11/2011 Towards integrated commodity ... - Se… The eggs are laid loose amongst the substrate or tucked into creases in the grain. The pale yellow, elongate larva passes through four instars feeding and moving freely and eventually pupates within a cocoonlike structure of small grains or food particles. After a preoviposition period of 54 days the female lays some 375 eggs (at 30C) over a life-span of 6-8 months but may be prolonged at low temperatures. The adult may overwinter in temperate areas in the fabric of the building or granary. The life-cycle can be completed over 20C to 37.5C, the optimum range being 31-34C. Development is relatively rapid and is completed in 22 days at 30C and 68 days at 20C (at 70% R.H.). The species is very tolerant of low humidities and even at 30C and 10% R.H., larval mortality is less than 15%. The adults rarely fly and during the day they tend to hide in cracks and crevices which enables them to escape the harmful effects of unfavourable temperatures and insecticide treatments. Aggregations occur at the edges of and in the dampest and warmest parts of a grain bulk and may contribute to grain heating. O. surinamensis is a cosmopolitan secondary pest of cereals, mainly milled products such as flour, meals, breakfast foods, stock and poultry feeds, copra, confectionery and dried fruits. (ii) O. mercator (Fauvel), The merchant grain beetle. Small (2.5-3 mm) brown beetle: may be distingguished from O. surinamensis which it closely D:/cd3wddvd/NoExe/…/meister11.htm 2/248 06/11/2011 Towards integrated commodity ... - Se… resembles, by the eye diameter being larger than the temple region behind the eye, the more triangular head and generally darker and slightly larger. Life-history and biology similar to that of 0. surinamensis but O. mercator has a lower rate of increase because of its lower fecundity and slower development. Thus, the female produces an average of only 200 eggs and development takes 23 days at 30C and about 100 days at 20C (both at 70% R.H.). Additionally, the species is less tolerant of low humidities and extreme temperatures than O. surinamensis and is therefore less important in temperate regions. O. mercator is more abundant in oilseeds, cakes and dried fruit than cereals and milled products although it will thrive in the latter. (iii) Ahasverus advena (Walt!), The foreign grain beetle. Small (2-3 mm) brown beetle: prothorax squarer than O. surinamensis and has only one prominent tooth at each apex. Generally regarded as a mould feeder attacking a wide range of commodities such as damp cereals or cereal products, copra, groundnuts, oilseeds and cakes, dried fruits, etc., but can breed in clean cereals provided that yeast or germ is present. At 25C and 70 R.H. development is completed in 35- 40 days but the species fails to breed below 60% R.H. A. advena, although cosmopolitan, is most abundant in tropical and warm temperate regions. D:/cd3wddvd/NoExe/…/meister11.htm 3/248 06/11/2011 Towards integrated commodity ... - Se… 9. TENEBRIONIDAE This is one of the largest and most important families of small to moderate sized beetles nearly always unicolorous black or dark brown with 11 segmented antennae (rarely 10-segmented) and are generally thickened or clubbed towards their apices. The elytra completely cover the abdomen, and there are five visible ventral abdominal segments. The front and middle tarsi are 5-segmented and the hind tarsi are 4-segmented. It is useful since it distinguishes members of this family from nearly all other stored products Coleoptera. They are particularly abundant in the subtropics, where most species are saprophagous, feeding on organic debris, and are also well adapted to dry conditions. Many are carnivorous; cannibalism being common, some are predators and others require their diet to be supplemented with insect remains. Almost 100 species have been recorded as stored product pests. Their size varies considerably from about 21 mm in Blaps mucronata to 2.8 mm in Alphitophagus bifasciatus. The larvae are cylindrical, generally sclerotized, yellow to brown, and compared with pests such as Sitophilus and Rhyzopertha, the adults are longer lived, producing eggs throughout most of their life and the larvae pass through many more instars. (i) Tribolium castaneum (Herbs"), The rust-red flour beetle. Small (2.3-4.4 mm) reddish-brown beetle. Antennae with distinctive 3-segmented club. Width of eyes (seen from below) about equal to the distance between the eyes. The lateral margins of the D:/cd3wddvd/NoExe/…/meister11.htm 4/248 06/11/2011 Towards integrated commodity ... - Se… head are nearly continuous at the eyes. The eggs, which are usually covered with particles and are laid singly. The larva, which is white to yellow and has rather obvious protruberances or horns on the terminal segment, passes through 6 or more instars. Newly emerged adults mate and start to lay eggs within 3 or 4 days. The adult may live for 14 months (average 9 months) and produces as many as 18 eggs per day during the first month of life when temperature, moisture and food supply are suitable. Although this high rate of egg production declines with increasing age the potential fecundity of any female may well exceed 1000 eggs. Both larvae and adults are cannibals and may consume eggs, young larvae and pupae. The life-cycle can be completed over 20-42 C but the optimum lies between 32-37.5C. Development from egg to adult takes 22 days at 34C (72% R.H.) and 50 days at 24C (76% R.H.). The adults fly readily at temperatures found 25C and are generally more numerous on the grain surface. Although cosmopolitan, T. castaneum, with its relatively high temperature optima is a pest of tropical or warm areas while in temperate or cold regions, it may be replaced by T. confusum. T. castaneum is a secondary pest of a wide range of cereals, cereal products, legumes, oilseeds and cakes, nuts, spices and animal products and is regarded as an extremely successful omnivore particularly abundant in warm and often dry conditions. Quinones secreted by the adults produce an unpleasant musty taint under high population densities. (ii) T. confusum Jacquelin du Val. The confused flour beetle. D:/cd3wddvd/NoExe/…/meister11.htm 5/248 06/11/2011 Towards integrated commodity ... - Se… Small (2.6-4.4 mm) flattened, oval, reddish brown beetle. Antennae without a distinct club, but expand gradually. The width of eyes (seen from below) about one third of distance between the eyes. The head margins are expanded and notched at the eyes. The head and upper parts of the prothorax are densely covered with minute punctures. Elytra ridged lengthways and sparsely punctate between the ridges. Life-history and biology essentially as for T. castaneum. However, T. consusum is less fecund than T. Castaneum and under favourable conditions lays only 14 eggs per day during the first month of life. The life-span is about 7 months but may exceed one year. Development from egg to adult may be completed from about 19C to 37.5C, the optimum lies between 30C and 34C. The life-cycle is completed in 26 days at 34C (72% R.H.) and in 54 days at 24C (76% R.H.). Under identical conditions of temperature and humidity T. confusum develops more slowly than T. castaneum. Development may be prolonged at low humidities but mortality is little different from that at optimal conditions. The adult seldom flies and the dispersal of the species is passive. T. confusum is less susceptible to cold than T. castaneum and although cosmololitan more abundant in temperate regions. A wide range of cereals cereal products, nuts, oilseeds and their cakes are attacked. Several other members of the genus are also troublesome on cereals and cereal products. T. audax (Halstead), the American black flour beetle, is commonly found both butdoors and in warehouses D:/cd3wddvd/NoExe/…/meister11.htm 6/248 06/11/2011 Towards integrated commodity ... - Se… and is often confused with the European T. madens (Charpentier) which it resembles in appearance, biology and habits. Both are essentially similar to T. confusum, but are larger (3.55.2 mm) and black in colour. Another European import is T.