Preparing the larval artificial diet of Euscepes postfasciatus involves two procedures: pre-processing of diet ingredients, and mixing and heating, both of which are complicated. To simplify the diet preparation, we compared the survival and development of E. postfasciatus among three versions of diet: the previous version (diet A), diet B in which three ingredients (dried sweet potato, vitamin mixture and salt mixture) were replaced by ready-processed commercial products without modifying the mixing and heating process, and diet C in which the mixing and heating were simplified using the same ingredients as for diet B. For diet B, the survival rate was higher and the development time was shorter than for diet A, indicating that replacing the ingredients favorably affects the survival and development of insects. The survival rate with diet C was between and did not differ significantly from diets A and B. Development with diet C was longer than with diet B, but did not differ significantly from that with diet A. These results indicate that survival and development with the diet prepared by a simple method is comparable to with the previous diet.
Scirpus juncoides Roxb. var. ohwianus is a cyperaceous weed species found in rice fields and has been reported as an alternative substrate plant for the egg deposition of the sorghum plant bug, Stenotus rubrovittatus. The seasonal occurrence of S. rubrovittatus and its damage to rice grains were investigated in S. juncoides-infested and non-S. juncoides-infested rice fields in 2005 and 2006. In S. juncoides-infested rice fields, the immigration of S. rubrovittatus adults started prior to the heading period of rice plants, and nymphs and adults of the next generation were also observed in the field. In non-S. juncoides-infested rice fields, S. rubrovittatus adults immigrated into the fields after the rice plant heading period and very few nymphs were observed throughout the survey period. The percentages of rice grains damaged by S. rubrovittatus in S. juncoides-infested rice fields were higher than those damaged by S. rubrovittatus in non-S. juncoides-infested fields. These results suggest that weed management in rice fields is essential for reducing the extent of plant bug damage to rice grains as well as for managing weeds in the original habitat of plant bugs.
We investigated the mating and oviposition behaviors of the sorghum plant bug, Stenotus rubrovittatus (Matsumura) (Heteroptera: Miridae) under 25°C and 16L8D conditions in the laboratory in order to use the synthesized sex pheromone effectively as part of the integrated pest management. The ethogram of male courtship behavior was composed of the following four steps: approach, antennae, hold, and mounting. Both the durations from paring to copulation and copulation durations were almost same in light and dark conditions, suggesting that S. rubrovittatus males recognized the mate by using factors except visual stimuli in the short distance. The copulation rate of virgin females increased with an increase in days after adult eclosion. Females that copulated once received no additional copulations within three days after the first copulation. No significant differences in the preoviposition periods and total numbers of eggs deposited were observed between virgin and copulated females, which were paired with a male during their lifetime or until the first oviposition. On the other hand, virgin females had significantly longer longevities relative to copulated ones. Most of the eggs deposited by single copulated females were fertilized, suggesting that a single insemination provided enough sperm to fertilize all the eggs produced by S. rubrovittatus females during their lifetime.
A method to promote flower visiting by honeybees Apis mellifera L. (Hymenoptera; Apidae) on eggplants was examined by conditioning honeybees to associate eggplant floral scents with sugar-water rewards. The fragrance components of eggplant floral scents were analyzed by coupling solid-phase micro-extraction techniques and gas chromatography-mass spectrometry. The main fragrance component of the whole flowers and pollen of eggplants was identified as geranylacetone. The effect of scents on foraging preferences was investigated by feeding honeybee colonies with sugar water including geranylacetone during the evening before the test day. Foraging honeybees from geranylacetone-conditioned colonies tended to visit feeding sites with geranylacetone scent more than feeding sites with linalool scent and only sugar water. Twelve geranylacetone-conditioned honeybee colonies were placed in eggplant greenhouses. Foraging honeybees from all 12 colonies started visiting eggplant flowers the following day. Unconditioned colonies fed only sugar water were tested as a control. In 5 of 12 unconditioned colonies, foraging honeybees started visiting eggplant flowers the following day. In the other 7 unconditioned colonies, foraging honeybees waited more than 2 days before starting to visit eggplant flowers. We conclude that conditioning honeybees to associate geranylacetone—the main fragrance component of eggplant floral scents—with sugar-water rewards promotes flower visiting.
A pest of cultivated shiitake mushroom Chaetosciara takahashii Sasakawa, 1992 (Diptera: Sciaridae) originally described on Hachij Island, Tokyo was recently recorded in Shizuoka, Miyagi and Iwate Prefectures, mainland Japan. The Palaearctic congeners C. estlandica (Lengersdorf, 1929) and C. umbalis Mohrig and Krivosheina, 1990 were recorded in Japan for the first time.