Articles

WING DIMORPHISM IN TUSCAN POPULATIONS OF RHYZOBIUS LITURA (FABRICIUS) (COLEOPTERA COCCINELLIDAE)


Abstract


Wing polymorphism is well known among beetle families such as Carabidae, Staphylinidae, Tenebrionidae and Curculionidae, but it is relatively uncommon among Coccinellidae. Rhyzobius litura (Fabricius) is one of the Italian Coccinellidae species, with a dimorphism involving the second pair of wings which may be fully developed (macropterous) or may assume a ribbon-like structure (brachypterous). Specimens of R. litura collected from localities of the Tuscan Archipelago (islands of Elba, Gorgona and Pianosa, Province of Leghorn) and Tuscan hinterland (Lorenzana, San Giuliano and Ponsacco, Province of Pisa) were examined for wing dimorphism. Different sampling techniques were used: Malaise traps, pitfall traps, beating tray, collecting net and visual search. Specimens collected were either adults or larvae, these latter were reared till maturity and then examined. Results showed a remarkable homogeneity within the examined populations, which were always constantly or strongly brachypterous or macropterous. Most of the populations examined were composed of specimens which were brachypterous or with a high level of brachyptery, but the population from the island of Pianosa was entirely composed of macropterous specimens. The hypothesis that the emergence of a long-winged population could be due to geographical isolation is discussed.


Keywords

Coccinellids, wing polymorphism, sampling techniques, Tuscan Archipelago.

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