|Morgan, Thomas - Tom|
Submitted to: Journal of Stored Products Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/20/2002
Publication Date: 2/1/2002
Citation: MORGAN, T.D., BAKER, P., KRAMER, K.J., BASIBUYUK, H.H., QUICKE, D.L. METALS IN MANDIBLES OF STORED PRODUCT INSECTS: DO ZINC AND MANGANESE ENHANCE THE ABILITY OF LARVAE TO INFEST SEEDS?. JOURNAL OF STORED PRODUCTS RESEARCH 39: 65-75. 2002. Interpretive Summary: Insect mandibles are used to damage and penetrate intact grain kernels. We have examined whether the ability of insect pests to attack kernels may be influenced by the presence of metals in the mandibular teeth. In a collaborative study with scientists in the UK, we show for the first time that not only adult but also larval mandibles of several stored product insect pests have high levels of zinc and/or manganese. Larvae that do not have such high levels of metals in their mandibles are less capable of penetrating whole kernels. The data demonstrate that metals apparently affect the hardness of insect mandibles, which in turn enhances the ability of stored-product insects to attack whole grain. This information could be useful for the development of pest control methods that diminish the ability of pests to deposit metals in their mandibles.
Technical Abstract: Metals such as zinc and manganese were abundant in mandibles of insect larvae that bore into seeds and were not abundant in mandibles of insect larvae that do not bore into seeds. High levels of these metals were present in the larval mandibles of a lepidopteran, the Angoumois grain moth (Sitotroga cerealella), and eight coleopterans, the lesser grain borer (Rhyzopertha dominica), cigarette beetle (Lasioderma serricorne), drugstore beetle (Stegobium paniceum), spider beetle (Gibbium aequinoctiale), warehouse beetle (Trogoderma variabile), cadelle (Tenebroides mauritanicus), larger black flour beetle (Cynaeus angustus), and cowpea weevil (Callosobruchus maculatus). Larvae of all of these species can chew into seeds. However, larvae of six other species of Coleoptera, the varied carpet beetle (Anthrenus verbasci), sawtoothed grain beetle (Oryzaephilus surinamensis), rusty grain beetle (Cryptolestes ferrugineus), red flour beetle (Tribolium castaneum), longheaded flour beetle (Latheticus oryzae), and granary weevil (Sitophilus granarius) seldom if ever had metal-enriched mandibles and hardly ever chew through the outer layer of seeds. The larvae of the granary weevil hatch and feed within seeds that were penetrated previously during egg deposition by the adults. In contrast, newly hatched larvae of the cowpea weevil and the Angoumois grain moth are unable to survive unless they penetrate the seed coat and begin feeding in the interior of the seed, and they had mandibles with very high levels of zinc. These data support the hypothesis that deposition of zinc and/or manganese in the larval mandibles enhances the larva's ability to penetrate seeds.