Toyomi Kotaki

To determine the duration of winter conditions necessary to achieve successful termination of diapause in Orius sauteri (Poppius) (Hemiptera: Anthocoridae), nymphs were subjected to a L12:D12 photoperiod at 18 °C and emerged females were maintained under the same conditions for 15, 30, 45, or 60 days. After the respective period, the females were subjected to a photoperiod of L16:D8 at 25 °C, and four parameters were evaluated: pre‐oviposition period, oviposition period, total number of eggs laid per female, and longevity. In females of all four groups of different rearing durations at 18 °C, oviposition commenced within 2 weeks. There was a strong correlation between the pre‐oviposition period and the duration of rearing at 18 °C, with the pre‐oviposition period of females reared for 60 days being 4.5 ± 0.7 days, which was equivalent to that of non‐diapause females. Although the pre‐oviposition period of females reared for a 30‐day period was approximately 10 days, these females laid the highest total number of eggs among the four treatment groups. Longevity was found to be negatively correlated with the length of rearing duration at 18 °C, whereas neither oviposition period nor total number of eggs per female was significantly correlated with the rearing duration. We subsequently subjected females collected in the field in late October to the same rearing conditions at 18 °C for 30, 45, 60, or 90 days, and accordingly found that the pre‐oviposition period of field‐captured females was longer than that of the laboratory‐bred females. However, the highest total number of eggs laid by field‐captured females was observed in those subjected to a 30‐day rearing period. Based on these observations, we can conclude that a period of 30 days under conditions of 18 °C is sufficient to induce diapause termination without reducing fecundity.

Juvenile hormone (JH) plays important roles in almost every aspect of insect development and reproduction. JHs are a group of acyclic sesquiterpenoids, and their farnesol backbone has been chemically modified to generate a homologous series of hormones in some insect lineages. JH III (methyl farnesoate, 10,11-epoxide) is the most common JH in insects, but Lepidoptera (butterflies and moths) and ‘higher’ Diptera (suborder: Brachycera; flies) have developed their own unique JHs. Although JH was first proposed in the hemipteran suborder Heteroptera (true bugs), the chemical identity of the heteropteran JH was only recently determined. Furthermore, recent studies revealed the presence of a novel JH, JH III skipped bisepoxide (JHSB₃), in some heteropterans, but its taxonomic distribution remains largely unknown. In the present study, we investigated JHSB₃production in 31 heteropteran species, covering almost all heteropteran lineages, through ultra-performance liquid chromatography coupled with tandem mass spectrometry. We found that all of the focal species produced JHSB₃, indicating that JHSB₃is widespread in heteropteran bugs and the evolutionary occurrence of JHSB₃ascends to the common ancestor of Heteroptera.

To clarify the role of Juvenile hormone (JH) in the induction of oosorption in females of the stink bug Plautia stali Scott (Heteroptera: Pentatomidae), the effects of extirpation and implantation of the corpus cardiac‐corpus allatum complex (CC‐CA) are examined in fed and starved adults, respectively. Removal of CC‐CA induces oosorption in fed females, whereas CC‐CA implantation stimulates ovary development in starved females. Transection of the nervous connections between the brain and CC‐CA also exerts a stimulatory effect on ovary development. Uptake of yolk protein by the oocytes, assessed in terms of incorporation of a fluorescence dye, occurs on the day after food deprivation but ceases within 1 day after allatectomy. When females are deprived of food, beginning on day 3 of adult life, and treated with JH III skipped bisepoxide (JHSB ₃ ) on the same day, their ovaries develop in a dose‐dependent fashion. Approximately half of the starved females that received JHSB ₃ application on day 5 undergo oosorption in the terminal oocytes. This indicates that the critical starvation period for oosorption induction is approximately 2 days, and the earlier half of this period may reflect the time required for the brain to detect poor nutritional condition. During the latter half, in response to food deprivation, the brain inhibits JH biosynthesis by the corpus allatum through nervous connections, resulting in a low JH titre, which in turn induces oosorption.

Juvenile hormone (JH), which occurs in several forms in different insects, is one of the most important insect hormones. The structure of JH in Heteroptera has not been elucidated until recently, although insects in this suborder have long been used as experimental animals for JH research. Here we review the structure determination of a novel JH in a stink bug,Plautia stali, which was named juvenile hormone III skipped bisepoxide [JHSB₃: methyl (2R,3S,10R)-2,3;10,11-bisepoxyfarnesoate], based on the arrangement of two epoxides at C2,3 and C10,11 with a skipped double bond at C6,7.

The structure of the juvenile hormone (JH) in the suborder Heteroptera, order Hemiptera, has been known for a very long time to be different from the JH of other orders, but the structure has been a matter of controversy. The structure was first elucidated by an unprecedented approach involving the screening of a JH molecular library. The novel Heteroptera-specific JH (JHSB₃) is a new category of JH that is featured by the skipped bisepoxide structure.