Taxonomic status of Dryocoetes autographus Ratz. and D. hectographus Reitt. (Coleoptera: Scolytidae)

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Abstract
The species status of D. autographus and D. hectographus is investigated by means of morphological and biosystematic methods. A hybridization experiment resulted in progeny, but the F1 generation appeared to be infertile. The size of the punctures on the elytral declivity and two dimensions of the endophallic portion of the penis were measured on specimens from the two forms and the hybrids. The declivital punctures show great variation with overlap. The shape of the penis in the two forms is distinctive and is therefore an excellent diagnostic character. The hybrids occupy intermediate positions to a great extent. D. hectographus is significantly longer than D. autographus. Olfactometer experiments showed that male Dryocoetes produce aggregation pheromones, and there was some cross-attraction between the two forms. Measurements of the supercooling points showed that significantly more D. hectographus were cold adapted. Electrophoretic analysis of both forms taken from the same breeding stock revealed a conspicuous and constant difference in the protein pattern, indicating that they are genetically distinct. It is concluded that the two species should still be considered as distinct.

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