Hair Suitability and Selection During Oviposition by <I>Hypoderma lineatum</I> (Diptera: Oestridae)

Abstract

Tethered females of the common cattle grub, Hypoderma lineatum (Villers), were allowed to oviposit on Hereford calves. The diameters of hairs selected for oviposition were compared with the diameters of randomly sampled hairs from the back of each animal. Also, the number of eggs attached to a hair was compared with the diameter of the hair to which they were attached. The mean diameter of hairs selected for oviposition was 0.07 ± 0.002 mm, whereas the mean diameter of randomly sampled hairs was 0.04 ± 0.001 mm. These means were significantly different, demonstrating that H. lineatum females rejected the more abundant narrow diameter hairs in favor of the relatively scarce larger diameter hairs during oviposition. The number of eggs deposited per hair increased linearly with increasing hair diameter, again demonstrating a propensity for selection of large diameter hairs during oviposition. Measurements of the circular area formed by the opposing, concave, hair grasping surfaces of the 9th sternites and 10th tergites resulted in a mean diameter of 0.10 ± 0.01 mm, conforming to the diameter of the largest hairs selected during oviposition. The possible selective advantages driving hair selection by H. lineatum are discussed as well as characteristics related to hair suitability and ovipositor tip morphology.