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Disruption of sex pheromone activity in female Rocky Mountain wood ticks, Dermacentor andersoni Stiles, and American dog ticks, Dermacentor variabilis (Say), was achieved by treatment with the quinones para-benzoquinone and menadione. The most effective treatments were those administered by inoculation to unfed, mature, adult females prior to feeding. Inoculation of p-benzoquinone was also effective when administered to feeding ticks, from 2 to 5 days after they had attached, though not to the same extent as when it was given to unfed ticks. Decreases in sex pheromone activity were also observed with D. andersoni females, but not D. variabilis females, allowed to feed on rabbits receiving menadione daily by oral administration. Histochemical studies and electron microscopy revealed loss of neutral lipid secretory droplets in the pheromone glands, but no damage to gland structure, following treatment with p-benzoquinone. Elemental analysis revealed more than four times as much chlorine in pheromone glands of p-benzoquinone-treated D. variabilis females than in pheromone glands from control specimens. An extract of partially fed D. variabilis females treated with p-benzoquinone before feeding contained much more 2,6-dichlorophenol than an extract of untreated, partially fed females. Evidently, the quinone affects the neutral lipid component of the female sex pheromone gland, disrupting secretion and release of pheromone to the external body surface.

The ultrastructure of the foveae dorsales and pheromone glands (foveal glands) of both feeding and unfed female Dermacentor variabilis (Say) was studied. Each pore of the fovea contains a pore tube, with cells surrounding a lumen that can be opened or closed. Each pore tube extends below the fovea and expands to form a cone-shaped ampulla, into which a duct of the foveal gland is inserted. Each duct is lined with microvilli, except near its insertion into the ampulla where the lumen is lined with a brush border. In the feeding female, numerous vesicles and lipid droplets accumulate in and around the ducts. However, in the unfed female, the ducts are free of vesicles or droplets. A nerve, the foveal nerve, occurs in the vicinity of the ducts. Neurosecretory vesicles occur in some of the nerve fibers in the feeding tick. Microorganisms, of unknown identity, were found near the ducts of the pheromone gland in feeding females, but not in unfed females. The secretory lobes of the pheromone glands, representing the major part of these organs, contain large cells which appear to comprise one type. In the feeding female, lipid droplets of varying size occur in vesicles or, more frequently, free in the cytoplasms. The may be clustered or scattered throughout large areas of the cell cytoplasm. Accumulations of vesicles and lipid droplets are especially abundant at the ends of the cells, near the junction with the ducts, where they may occur in a single large membrane-bound enclosure. In the unfed female, the lipid droplets occur only within vesicles, distributed more or less uniformly throughout the gland cells.

The foveal glands of Dermacentor variabilis appear to consist of 2 cell types. The outer cells (Type I) are active, with large areas of abundant finely granular material, apparently precursors of the mature secretory granules. The inner cells (Type II) are apparently storage cells. They are highly vacuolated and contain coarsely granular material as well as presumably mature secretory granules. The foveal glands of D. andersoni contain only Type II cells with extensive accumulations of presumably mature secretory granules.