Abstract:

Effects of adult body size on the reproductive fitness and offspring development in the Coleopteran parasitoid Dastarcus helophoroides (Fairmaire) (Coleoptera: Bothrideridae) were investigated through pairing the biotype adults of Monochamus alternatus according to three levels of body weight at constant temperature condition and recording the parameters of parental reproductive fitness and offspring development in nine treatment combinations. The results showed that, with respect to adult reproductive fitness, the proportion of oviposition (＞60%) of the adult pairs with the same body weight was significantly higher than that of the pairs with body weight incompatibility (＜50%). Significant differences were found in the proportion of oviposition when smallfemales and males were paired with big, moderate and small partners. There was no significant difference in pre-oviposition period among the nine pairing treatments, while the egg production significantly decreased by 41.20% with decreasing female body weight, and increased by 69.92% with decreasing male body weight, but was not affected by the comprehensive impacts of both sexes. With respect to offspring development, the pre-hatching duration (10.80―11.36 d), the hatching duration (2.57―3.08 d), and the hatching rate (64.36%―75.45%) showed no significant difference among the nine pairing treatments. However, the percentage of parasitism of the offspring larvae decreased significantly from 96.77% to 86.5% with decreasing female body weight. The percentage of pupation and emergence significantly decreased from 76.47% to 56.55% and from 75.33% to 56.55% with decreasing female and male body weights, respectively, but were not affected by the comprehensive impacts of both sexes. The developmental duration of larva-pupa significantly extended from 45.69 d to 47 d with the weight loss of parental generation. The body weight, body length, and body width of female offspring were not affected by the weight loss of parental generation, while the body weight of male offspring was affected by their maternal body weight, and the body length was affected by their parental body weight. These results demonstrate that the ectoparasitoid beetle displays size-assortative mating and the body weight of the beetle has a profound effect on reproductive fitness and offspring development. Therefore, cautions have to be exercised to avoid the negative influences incurred from the difference in body size of the beetle during large-scale breeding by selecting large adults to improve the quality of offspring.

Key words:

 Dastarcus helophoroides, body size, reproductive performance, growth and development, morphological development