Anatomical and Histological Comparison of the Alimentary Canal ofDendroctonus micans,D. ponderosae,D. pseudotsugae pseudotsugae,D. rufipennis, andD. terebrans(Coleoptera: Scolytidae)

The anatomy and histology of the alimentary canal of Dendroctonus micam (Kugelann), Dendroctonus ponderosae Hopkins, Dendroctonus pseudotsugae pseudotsugae Hopkins, Dendroctonus rufipennis (Kirby), and D. terebrans (Olivier) were described and compared. Characteristics in the structural organization of the alimentary canal in these species are comparable with those in previously studied Dendroctonus species. However, important histological differences not found in other scolytids were observed in the esophagus, crop, proventriculus, midgut, and hindgut of these species. Particularly, spines in the esophagus and crop, chitinous plates in the proventriculus, great cellular diversity in the midgut, and fine spines located in the cuticle surrounding the hindgut valve in the anterior hindgut are unique characteristics of Dendroctonus species. In the species studied, the ratio of foregut, midgut, and hindgut in relation to the total length of the alimentary canal varied slightly. This ratio did not show a relationship with insect size. Differences among the diameters of each gut region were statistically significant (P < 0.05), and the largest diameters did not necessarily appear in the largest species.