Oviposition and Orientation of the Cereal Leaf Beetle

Author： WELLSO STANLEY G. CONNIN RICHARD V. HOXIE ROBERT P.

Publisher： Entomological Society of America

ISSN： 1938-2901

Source： Annals of the Entomological Society of America, Vol.66, Iss.1, 1973-01, pp. : 78-83

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Abstract

The orientation of the cereal leaf beetle, Oulema melanopus (L.) (Coleoptera: Chrysomelidae), during oviposition in the laboratory on seedlings of ‘Hudson’ barley, ‘Clintland’ 64 oats, or ‘Genesee’ wheat was similar, based on egg position. Oviposition on the blade apex of all 3 plants was less than on the other 4 transverse regions, but only 15% of the eggs were deposited on the blade base when the seedlings were illuminated from overhead compared with over 40% when they were illuminated from the side. When the width of the barley blade was decreased by removing the blade on one side of the midvein for the length of the leaf, oviposition on the narrow blades was reduced nearly 8-fold. The orientation of ovipositing beetles confined with inverted seedlings was inferred from the position of the egg; that these beetles had difficulty ovipositing was detected by the 3-fold increase in fallen or horizontal eggs. Also. the inversion forced the beetles to choose to oviposit either with or against gravity, and given this choice, nearly 50% of the eggs were deposited by beetles oriented upside down. Thus, the orientation of the host was found to modify female oviposition behavior. About 12% of the oviposition occurred during the scotophase of a 16-hr light:8-hr dark photoperiod at 26.7°C, and 76% of the eggs deposited during scotophase were deposited in the first half of this interval. Beetles that fed and overwintered in the field and then initiated normal spring oviposition, oviposited twice as long, an average of 34.3 days, as beetles from the same generation collected in the field and fed and stored in the laboratory about 20 weeks. The daily average number of eggs deposited per female ranged from 8.7 to 12.2 eggs.