Attraction of Bucephalogonia xanthophis (Hemiptera: Cicadellidae) to volatiles of its natural host Vernonia condensata (Asteraceae)

Plant volatiles are important cues for the orientation of herbivorous insects. It is possible that these compounds indicate whether the plant is suitable for feeding and larval development, or for mating aggregation. Vernonia condensata (Asteraceae) is known to attract species of leafhoppers, most of them important vectors of the citrus variegated chlorosis (CVC). In this study, we evaluated the role of volatiles of V. condensata on the orientation of Bucephalogonia xanthophis (Hemiptera: Cicadellidae). Four-arm olfactometer bioassays showed that only males were attracted to the volatiles of the host-plants Citrus sp. and V. condensata. Furthermore, fresh leaves of V. condensata induced a stronger response than volatiles from hexane-extracted leaves. This study opens the possibility to utilize V. condensata volatiles for pest management programs of B. xanthopis.

Aggregative Mating of Tanner Crabs, Chionoecetes bairdi

In April 1991, a high-density mating aggregation of Tanner crabs, Chionoecetes bairdi, was discovered at 150 m depth near Kodiak, Alaska, with the research submersible DSRV Delta. The aggregation consisted primarily of oldshell, multiparous female crabs which formed mounds 1–2 m in diameter, 0.5–1.0 m high, and spaced at intervals of 1–2 m. Mounds contained hundreds of crabs each at densities > 100∙m−2. Male crabs were found mating with females at the periphery of the aggregation, with sex ratios (male to female) varying from 1:10 to 1:100. The entire aggregation covered an area of about 2.2 ha and included approximately 100 000 crabs. No mounds were observed in May 1992, but recently spawned female crabs were found buried in the sediment at high densities (up to 2.2∙m−2) over an area of about 25 ha, suggesting that aggregation had reoccurred at the same location. Newly ovigerous females exhibited a cycle of nocturnal activity and diurnal burial whereas unmated crabs remained exposed on the sediment surface. Many body parts and presumably dead crabs were observed. We conclude that aggregative mating is a major mode of reproduction in the family Majidae.

Morphometry and Maturity of Paired Tanner Crabs, Chionoecetes bairdi, from Shallow- and Deepwater Environments

Paired male and female Tanner crabs, Chionoecetes bairdi, in a premating embrace were collected from shallow-(< 13 m) and deepwater (> 150 m) benthic environments by scuba and submersible, respectively. Pubescent females were restricted to shallow water; males grasping them were significantly smaller than those grasping oldshell multiparous females with eyed embryos in a large, deepwater mating aggregation. Males appeared to select for large sizes among pubescent females, but not among multiparous females, which were limited in size range. Grasping males were 82.6–166.2 mm carapace width (CW) [Formula: see text] and represented at least three different width frequency modes; all were larger than their female partners. Paired females represented two modes with mean CW ≈ 77 mm for pubescent and 99 mm for multiparous individuals. Only one to three of 176 male graspers were small-clawed (morphometrically immature), a statistically nonsignificant proportion; several others had partially regenerated claws but were otherwise morphometrically mature, as evidenced by the second right merus. These data support the hypothesis that the attainment of morphometric maturity, evidenced by a relatively large chela to body size ratio, is a prerequisite for functional maturity, the ability to mate competitively in wild populations.