STUDIES ON ARTHROPOD CUTICLE. VIII. THE ANTENNAL CUTICLE OF HONEYBEES, WITH PARTICULAR REFERENCE TO THE SENSE PLATES

¹ Division of Entomology and Economic Zoology, University of Minnesota, University Farm, St. Paul 1, Minnesota

1. The epicuticle on honeybee antennae differentiates in correlation with sclerotization to give qualitatively different reactions on different parts.

2. The procuticle of the antennae shows a novel and unorthodox sequence of sclerotization involving two stages. The first stage begins at the outer surface and spreads inwardly, the second begins at the inner surface and spreads outwardly (Figs. 40-46). As a result the entire thickness of cuticle becomes sclerotized but still shows reducing power for osmic acid and ammoniacal silver nitrate. In contrast, the cuticle of thorax and abdomen shows the orthodox sequence of sclerotization proceeding from the outer surface inwardly.

3. Argentophile granules disappear during sclerotization from epidermal cells of areas that undergo sclerotization. Large numbers of argentaffin-positive granules remain in the cell cluster under the sense plates.

4. In the strip containing sense plates, the antennal cuticle develops a dark brown color in its inner half. This browning, which is additional to the usual sclerotization, is not found in the strip which is devoid of sense plates.

5. The cuticle over sense hairs and sense pegs becomes completely sclerotized; the cuticle over sense plates and sunken setae undergoes only the first of the two stages involved in sclerotization.

6. It follows that the cuticle over chemoreceptors cannot be assumed to have the same penetration properties as cuticle on other parts of the body. Also, different sensilla with cuticles of similar thickness cannot be assumed to have similar-penetration properties.

7. The color of sclerotized antennal cuticle is not noticeably affected by prolonged treatment with hot water (100° C.) but lack of complete resistance to the reatment is shown by a change from near isotropic to readily recognizable birefringence.

8. The sense plates are differentiated early in the formation of the adult cuticle. They develop a complicated micelle pattern involving both radial and tangential orientations (Fig. 4). Other sensilla also differentiate early.

9. Balken are divisible into smaller fibrils of micellar dimensions. Viewed from the surface they form a crossed-fiber pattern on the antenna with four recognizable orientations: longitudinal, circumferential and two oblique (Fig. 1). At the ends of the segments these Balken fuse into rims which show completely circumferential orientation; the rims in turn join intersegmental membranes which show completely longitudinal orientation.

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