Taxonomy
provided by EOL authors
The saw-toothed grain beetle belongs to the genus Oryzaephilus of the family Silvanidae, to the sub-family Silvaninae of the Cucujidae. Some history. Linnaeus (1767) made the original description of the species at which time he placed surinamensis in the genus Dermestes. He received specimens of this insect from Surinam (Dutch Guiana) and for that reason gave it the specific name surinamensis. This species was described under several names after Linnaeus account. Geer (1775) placed it in the genus Tenebrio and named it Tenebrio surinamensis. Fabricius, in the same year (1775), described it as Anobium frumentarium. Oliver (1790) named it as Ips frumentaria. Fabricius (1792) placed it in still another genus, referring to it as Colydium frumentarium and in the same year (1792) he described the same species under the names Dermestes sexdentatus and Scarites cursor. Kugelann (1794) described it as Lyctus sexdentatus, Paykull (1800) as Colydium sexdentatum, and Gyllenhal (1813) as Silvanus sexdentatus. Stephens (1830) followed Gyllenhal in placing the species in genus Silvanus and used the specific name surinamensis, and from then until comparatively recently it was known as Silvanus surinamensis. In 1899, Ganglbauer divided the genus Silvanus into two subgenera, Oryzaephilus with six teeth on the lateral margins of the thorax, and Silvanus with two or none, and placed the species surinamensis in the new subgenus Oryzaephilus. Reitter (1911) raised these two subgenera to the status of genera, and the saw-toothed grain beetle is now known as Oryzaephilus surinamensis.
Life Cycle
provided by EOL authors
Egg Eggs are generally white in colour, becoming ochre-yellow as they age, symmetrically oblong about 0.71 mm long and 0.24 mm wide at their broadest diameter with the anterior and posterior ends of almost identical shape, regularly rounded, or with the anterior end slightly narrower. Freshly laid eggs are glossy, smooth, non-opalescent, with both ends pellucid. During embryo development, eggs lose their gloss. An oblong depression is usually formed on the ventral side. The dark red eyespots and the ochre spot of mouth parts (mandibles and cibarial sclerite) are visible through the chorion at the anterior end (Kucerová & Stejskal 2002). Eggs are laid loosely in flour or other food product, or are lodged in crevices in whole grain. The female lays approximately 400 eggs either loosely in flour or other milled grain products or tucked in a crevice of a grain kernel (SGRL-CSIRO, Lyon-undated, Mason 2003). Egg laying begins about 5 days after emergence and reaches a maximum during the 2nd or 3rd week and then declines rapidly after about 10 weeks (Mason 2003). Eggs hatch in 3 - 8 days (Anon. 2009, Lyon-undated, Mason 2003) and the larvae begin to feed within a few hours of hatching (Mason 2003). Larva There are usually 3 or 4 larval instars. Larvae are creamy white in colour with a brown head and 3 pairs of legs. Larvae pupate without forming a special chamber (Halstead 1993). Tergites of abdominal segments 2-7 bearing four long setae antero-laterally, inner pair shorter (Cutler 1971). Larvae are typically free-living, mobile and not concealed. They are unable to develop on undamaged wheat (Surtees 1965, SGRL-CSIRO, Mason 2003). Under favourable conditions, larvae complete their development in 12 – 15 days. Pupa A pupal case is formed from bits of food material glued together and the pupal stage lasts from one to three weeks; total development time from egg to adult varies from 21 to 51 days, depending on temperature (Calvin 1990, Lyon-undated) Adult Length 2.2-3.1 mm, males slightly more elongate than females; usually dark brown; setae golden; dorsal side moderately shining to dull, ventral side shining. Head in males about as broad or broader than long, but in larger females may be slightly narrower than long; genae moderately raised in both sexes; slight depressions above antennal insertions; clypeus shallowly emarginate; eyes large, prominent, up to 3 times as long as broad; temples short, about one-quarter of eye length; antennae with club segments transverse, other segments particularly 8, variable; vertex with shallow punctuation; area of frontal triangle behind antennal depressions has most punctures smaller than eye facets; ventrally head reticulate punctuate; maxillary palps; 11-segmented antennae with segments 9 and 10 broader than in O. surinamensis, with their lateral margin outlines angled when viewed dorsally; club segments transverse but segment 8 and others variable. Pronotum slightly more elongate in males than females; median ridge well developed, frequently as high or higher medially than lateral ridges; lateral ridges pronounced, weakly curved laterally; anterior angles (tooth 1) moderately developed; punctures similar to that at sides of head. Elytra slightly longer than in O. surinamensis, elytral margin may be slightly produced before junction with suture; 3rd and alternate interstriae, slightly raised; setae decumbent, at sides of and along raised interstriae frequently overlapping, usually not appearing rigidly ordered. Prosternum obviously depressed between anterior margin and process; prosternal process raised at basal third, where procoxae inserted (Halstead 1980, Halstead 1993, Slow 1958). Adults live six to 10 months.
Distribution
provided by EOL authors
The saw-toothed grain beetle occurs worldwide. The biology of O. surinamensis suggests a tropical origin as it is most similar to an African species (O. parallelus) and a Middle Eastern species (O. abeilli) (Halstead 1980).
Biology and Morphology
provided by EOL authors
The biology of O.surinamensis has been studied in detail by Howe (1956) who found that eggs hatched at temperatures from 17.5 to 40 °C. Low humidity had little effect on the egg period and did not affect the length of the stadia. He observed that the preoviposition period at 30 and 33 °C was 3 to 8 days, usually about 5. O.surinamensis reached a peak of 6 to 10 eggs per female per day. The oviposition period he observed was over 2 months. The average number of eggs laid was about 375. The usual number of larval moults before pupation was 3, but a few individuals had 4 or 2. The optimum temperature for O.surinamensis is about 30 to 35° C. On coconut meal at 30 °C and 70% R.H., he found O.mercator grew faster than O.surinamensis. Both species could not complete development on groundnut meal unless yeast powder was added. On weighing adults, Howe found that Oryzaephilus beetles weighed only about 0.3 to 0.5 mg, he made no mention of either species or sex; these could not be weighed with accuracy, he claimed, since no torsion balance was available to him. The length of individuals of adults has been studied by many authors. Back and Cotton (1926) gave the average length of O.surinamensis as about 2.54 mm. Haydak (1936) gave the average length of O.surinamensis as 2.20 mm for the male, 2.26 mm for the female. Slow (1958) found that the adult of O.surinamensis was from about 2.75 to 3.25 mm long. Slow (1958) working on the morphology of adult O.surinamensis and O.mercator, measured the eye/temple ratio and round that it differed considerably in the two species. She found no other measurement or ratio which did not overlap. The male genitalia of some Cucujidae have been described by Sharp and Muir (1912), Tanner (1927), and Wilson (1930), and all of them observed that the male genital structures in the species are of a highly complex character. Agrawal (1955) gave a more detailed description of the male genitalia of O.surinamensis. The saw-toothed grain beetle is quite resistant to low temperature. De Ong (1921) working with cold storage control of insects, claimed that an exposure of 3 months at temperatures or 10° to 36° F. was needed to kill the larvae, pupae, and adults of this insects. Back and Cotton (1926) found that all stages of O.surinamensis were killed in 1 week within a temperature range of 20° to 25° F., and exposure to 0° to 5° F. killed all stages in l day. Thomas and Shepard (1940), working on the lethal effects of low temperature on the adult stage of O.surinamensis, found that adult saw-toothed grain beetles exposed at 10 °C and 2 °C gave 50 per cent mortality values at 30 days and 105 hours respectively. Solomon and Adamson (1955) exposed Oryzaephilus to winter conditions in various kinds of buildings in Britain, and found that O.surinamensis survived in all their tests.
Oryzaephilus surinamensis: Brief Summary
provided by wikipedia EN
Oryzaephilus surinamensis, the sawtoothed grain beetle, is a beetle in the superfamily Cucujoidea. It is a common, worldwide pest of grain and grain products as well as chocolate, drugs, and tobacco. The species's binomial name, meaning "rice-lover from Suriname," was coined by Carl Linnaeus, who received specimens of the beetle from Surinam. It is also known as the malt beetle and may be referenced in the poem This Is The House That Jack Built in the line "....the rat that ate the malt that lay in the house that Jack built" the malt referenced may not be actual malted grain but a sawtoothed grain beetle.
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