Description of a Gland Associated with the Foveae Dorsales in 2 Species of Dermacentor Ticks, and its Possible Role in Sex Pheromone Activity (Metastigmata: Ixodidae)1

Abstract

Histological evidence concerning the existence of a pair of small glands associated with the foveae dorsales in females of Dermacentor variabilis (Say) and Dermacentor andersoni Stiles is described. Each gland comprises several lobes linked to the ducts and pores of the fovea by filamentous protoplasmic connections. In the unfed females, the gland appears to be very small, flattened and compressed in the cuticular recess below each fovea. In partially fed females, however, the gland appears to grow until it has increased to approximately 3 times in depth and 2.5 times in breadth at the end of the 5th day of attachment. Masses of intensely staining granular material were visible in the gland cells and colloid-like substance accumulated in the foveal ducts in hematoxylin-eosin stained sections of partially fed females. Scanning electron microscopy of the foveae dorsales of unfed D. andersoni females revealed the presence of narrow, slit-like openings, oriented approximately in the direction of the anterior-posterior axis. No evidence of foveae dorsales could be found in males of either D. variabilis or D. andersoni. The Possible role of the glands in relation to sex pheromone activity in ticks is reviewed.