Guarding behavior is an important activity in sub-social insects, and this behavior is believed to improve the survival of offspring. Sclerodermus harmandi (Hymenoptera: Bethylidae) is one of most powerful epizoic parasitoid wasps, and it parasitizes Monochamus alternatus, a borer of wood and also the primary vector of the pinewood nematode Bursaphelenchus xylophilus. After laying eggs, S. harmandi exhibits sub-social behavior involving the female tending the clutch of eggs until emergence (guarding behavior). In this study, the benefits of this maternal care with regard to improvements in the survival of offspring were examined. During the developmental stages, only offspring in the egg and larval stages were sensitive to guarding behavior. A positive relationship between the survival of the offspring and the duration of guarding was detected with logistic regression analysis. A female replacement experiment demonstrated that multiparous S. harmandi stepmothers showed guarding behavior and that this behavior improved the survival of the immature offspring, whereas nulliparous stepmothers failed to exhibit the guarding behavior. These results indicate that S. harmandi females display maternal care and that this behavior improves the survival of offspring.

The Bipolaris setariae NY1 strain, isolated from a diseased green foxtail plant in Henan Province, China, showed strong pathogenicity towards green foxtail. In order to clarify the role of phytotoxic substances in the fungal pathogenicity, bioassay-directed isolation and bioactivity assays of secondary metabolites produced by the fungal strain were carried out. Five ophiobolins were obtained: 3-anhydro-ophiobolin A, 6-epi-ophiobolin A, 6-epi-ophiobolin B, 3-anhydro-6-epi-ophiobolin B and ophiobolin I. Bioassays on punctured and intact detached leaves of green foxtail indicated that 3-anhydro-ophiobolin A was the most phytotoxic, followed by 6-epi-ophiobolin A. The other three ophiobolins appeared to be inactive against green foxtail. The effects of 3-anhydro-ophiobolin A and 6-epi-ophiobolin A were synergistic. The symptoms on green foxtail caused by 3-anhydro-ophiobolin A or its mixture with 6-epi-ophiobolin A resembled those caused by the fungus. 3-Anhydro-ophiobolin A and 6-epi-ophiobolin A are likely the main pathogenic determinants of B. setariae. 6-epi-Ophiobolin A caused cytotoxicity against five kinds of human cancer cells: human colon adenocarcinoma cells (HCT-8), human liver cancer cells (Bel-7402), human gastric cancer cells (BGC-823), human lung adenocarcinoma cells (A549), and human ovarian adenocarcinoma cells (A2780). The results provide information for the development of herbicides and antitumor potential of the ophiobolin sesterterpenes.