Abstract: Experiments in the laboratory were conducted by continuously observing the larva-translocation behavior during maternal care in an ectoparasitoid Sclerodermus guani, with the goal of determining the developmental stage of offspring when larva-translocation behavior is initiated and exploring the rhythm of the behavior. Tenebrio militor pupae aged less than 24 hours were used as the host. The parasitoid larvae were divided into four groups according to their developmental maturity, i.e., young larva (1st-2nd instar), old larva (3rd-4th instar), mature larva (naturally dislodged) and spinning larva (starting spinning cocoon after dislodged). Parasitoid larvae treated were dislodged artificially (for young larvae) or naturally (for old larvae) from the host. A female wasp was continuously recorded for larva-translocation behaviors using video camera, and then analyzed by playbacks. The results showed that the female wasp patted larvae of all stages with its antennae, but did not move the young larva. The female exhibited a strong tendency to move the mature larva, with an instant probability of 4.09 times as high as that to move the old larva. The instant probability of moving the spinning larva was 7.69 times as high as that of moving the old larva. The proportion of larvae moved was 96% for the old larva and 100% for both mature and spinning larvae, without a significant difference between them (P≥0.05). The time the female parasitoid spent on a larva-translocation was on average 27.96 s for the old larva, 34.04 s for the mature larva, and 32.49 s for the spinning larva, without significant differences between them (P≥0.05). The larva-translocation distance, the direct length by which a larva was moved, was 4.19, 7.18, and 9.43 mm for the old, mature, and spinning larva, respectively; there was no significant difference between the first two (P≥0.05), but there was between the first two and the last (P<0.05). The linear trend analysis showed that there was a significant decreasing trend in the number of larvae tapped before translocation, but not in the larva-translocation duration and distance. There was a significant autocorrelation at lag 1 and 2 in the number of larvae tapped before translocation, and at lag 1 in the larva-translocation duration, but not in the larva-translocation distance. The results of this study suggest that S. guani females do not initiate larva-translocation behavior until their offspring larvae mature, and some behaviors of larva-translocation may be rhythmic.

Key words: Parasitoid, Sclerodermus guani, maternal care, larva-translocation behavior, behavioral rhythm, social behavior