A Preliminary Study On Maternal Care Behavior Of The Parasitoid Sclerodermus Guani Xiao Et Wu (Hymenoptera:Bethylidae)

The parasitoid Sclerodermus guani Xiao et Wu (Hymenoptera:Bethylidae) is one of important parasitic natural enemies of stem-boring coleopteran pests in forests of China. It has been widely used in the biological control of forest insect pests across China mainland. Though numerous studies have been carried out, producing rich publications, many of which are only involving simply observing of life history and qualitative describing of behavior, few studies have been made on behaviors in detail. Therefore, this thesis focused on maternal care behaviors of S. guani by investigating costs and benefits, timing of larval-translocation and rhythm and parent-child relation. This study will provide data for understanding of the evolution of social behavior in parasitoids, and also offer basic information for the mass-production of the parasitoid in biological control practices.1. Costs and benefits of maternal care behavior in the pareasitoid S. guani Treatment level of the study for whether the offspring larva with the mother or not, and then observing the fecundity of maternal and the development fitness of offspring, in this case we have found that:(1) The lifetimes of maternal wasp don’t have any difference, which is26.64d and28.85d. But. the numbers of larva of maternal care wasp is significant lower than inmaternal care wasp, because the maternal care wasp could only autoeciousness2times and the inmaternal care wasp could autoeciousness4times;(2) With maternal care, the development of offspring would enhance, because the death proportion, cocoon propprtion and the weight of offspring are respectively9.29%,61.52%and0.64mg. which is significant beter than the control group, which are respectively22.04%,27.4%and0.55mg, but, there don’t have difference in the emergence rato of larva and the paroportion of female in offspring between with or without maternal care.2. Initiation and rhythm of larva-translocation behavior during maternal care in the ectoparasitoid S. guani Experiments in the laboratory were conducted by continuously observing the larva-translocation behavior during maternal care in the ectoparasitoid Sclerodermus guani, with the goal of determining at which developmental stage of offspring was the larva-translocation behavior initiated and exploring the rhythm of the behavior. Tenebrio militor pupae aged less than24hours were used as the host. The parasitoid larvae were manipulated as four categories along the developmental stage, including young larva (1st-2nd instar), old larva (3rd-4th instar), mature larva (naturally dislodged) and spinning larva (starting spinning cocoon after dislodged). Parasitoid larvae were treated as being 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 with its antennae larvae of all categories, but did not move the young larva. The female exhibited a strong tendency to move the mature larva, with a instant probability of4.09times as high as that to move the old larva. The instant probability of moving the spinning larva was7.69times as high as that of moving the old larva. The proportion of translocating larvae was96%for the old larva and100%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 average27.96s for the old larva,34.04s for the mature larva, and32.49s 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, was4.19,7.18, and9.43mm 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 tapping larvae before translocation, but not in the larva-translocation duration and distance. There was a significant autocorrelation at lag1and2in the number of tapping larvae before translocation, and at lag1in the larva-translocation duration, but not in the larva-translocation distance. The results of this study suggested that S. guani females do not initiate the larva-translocation behavior until their offspring larvae mature, and some behaviors of the larva-translocation may follow the cyclic rhythm.3. Comparison in the larva-translocation behaviors between natural and step mother wasps in S. guani After laying eggs mother wasp were exchanged between the broods and a continuous observation using video camera was made. that the results showed that:(1) There was not a significant difference in proportion (>95%) of translocating larvae between natural and step mother;(2)Feeding would enhance the behavior of maternal care, the rato of larva-translocation are respectively50%,70%,100%,95%,95%, the rato of larva-translocation in Host-prefeeding is significant difference to pre-oviposition, young larva, old larva, spinning larva and the difference among pre-oviposition, young larva, old larva, spinning larva is insignificant;(3) The same as natural mother wasp, larva-development stage also largly influence the behavior of step mother and the difference between natural and step mother is insignificant. Such as, no matter the mother wasp is natural or step,the rato of larva-translocation is0%to young-larva and the rato of larva-translocation all is over95%to old-larva, mature-larva and spinning-larva, wich make a significant difference between young larva and others;(4) In the care of step mother, the offspring mortality is11.06%and the weight of offspring is0.634mg which is better than without mother wasp(21.56%and0.553mg), and the defference is insignificant between natural and step mother. In the same time, some week differences are also existing between natural and step mother, the larva-probe time of step mother to young larva and old larva (respectively29.09and86.62min) are significant higher than natural mother’s(15.32and42.39min) and the frequency of larval-translocation of step mother(83.48) is also significant shorter than natural mother’s (176.08) in600min.(5) As the increasing of larva-translocation, the interval time between larva-translocations, frequency of larva-probing and duration of larva-probing would decrease significant(coefficient is0.20,0.95and0.98, respectively), and, the duration of larva-translocation and distance of larva-translocation would increase significant(coefficient is1.18and1.01), but there also have some difference between natural and step mother wasp. Namely, as the increasing of larva-translocation, the frequency of larva-probing, duration of larva-probing, the duration of larva-translocation and distance of larva-translocation is significant different between natural and step mother, the step mother’s is respectively0.70,0.84,1.18and0.07times to natural mother’s.