Eighteen species of mesostigmatids, 22 of cryptostigmatids and one of astigmatids fed on soil nematodes. All mesostigmatids and astigmatids and 7 species of cryptostigmatids devoured whole living nematodes, whild the remaining cryptostigmatids fed only on their body fluids. No mites fed on sedentary forms of nematodes such as cysts Heterodera or adult females of Meloidogyne. Caloglyphus sp. (Astigmata) took 8 days of complete its life cycle when feeding on the nematode Cephalobus sp. at 23°C. When populations of Caloglyphus sp. and Cephalobus sp. (Nematoda) were mixed and inoculated into the soli, the nematodes decreased in number. The number of hypopi of Caloglyphus sp. increased when the mite had not been served with food (nematodes).

View full abstract

The mating behavior of three species of delphacid insects, Nilaparvata lugens, Laodelphax striatellus and Sogatella furcifera, was studied under laboratory conditions. It was demonstrated that both sexes of these species emitted species-specific vibratory signals perceived by the opposite sex as substrate vibrations. Most males of the three species emitted signals within five minutes after placed on a rice plant regardless of the presence or absence of other individuals. Stationary virgin females responded to make signals of the same species by performing abdominal vibration (FAV) by which signals were emitted. Males responded to female signals by moving toward females on rice plants. Males stopped moving and emitted signals immediately after female signals ceased. Thus, alternate signal emission by both sexes was continued until males came in close proximity to females. Males always emitted postcopulatory signals to which mated female partners showed no behavioral respones. Normal mating behavior was performed both under fluorescent light and under darkness. In N. lugens, the entire process of mating behavior was observed on a sheet of thin paper without rice plants. Sexually mature virgin females responded to the playback of recorded male signals of the same species only when the signals were transmitted as substrate vibrations. Mated females and females of other species never reponded to the signals. Although females emitted signals by monotonous vibration of whole abdomen (FAV), males emitted signals by vibration of specialized tymbal organs on the 1st and 2nd abdominal terga.

View full abstract

The timing mechanism of sexual calling by female L. candida was investigated in the laboratory. Experiments with several photoperiods indicated that the timing of female calling was primarily determined by the transition from light to dark. Female calling was inhibited by light, and was considered to reflect an endogenous circadion periodicity.

View full abstract

The wing form of Pteronemobius taprobanensis was influenced by a photoperiodic change. Macropterous adults were few in number either long-day (16L : 8D) or short-day (12L : 12D) conditions, but very common when there was shift in photoperiod from a long to a short one or vice varsa in the middle stage of nymphal development. The induction of the macropterous form by a short-day following 10 long-days after hatching was completed in about a week.

View full abstract

The smaller brown planthopper, Laodelphax striatellus, exhibited egg deposition into a 5% sucrose solution through a Parafilm membrane, however, when a mixture of amino acids was added to the 5% sucrose solution, no eggs were laid. Among 23 individually tested amino acids, arginine, glutamic acid, tyrosine, and valine showed an inhibitory effect upon oviposition, whereas the influence of cystine was stimulative.

View full abstract

Aggregate formation of the 1st instar larvae of Eurydema rugosa was induced by both olfactory and tactile responses rather than visual perception. The chemical stimuli responsible for the aggregation were derived from scent components produced by the stink bugs themselves. These chemical substances were considered as "aggregation pheromone." trans-2-Hexenal, one of the major components of the scent of E. rugosa, had roles of "attractant" and "arrestant". The same aldehyde was reported to have an alarm effect for aggregating larvae of R. rugosa (ISHIWATARI, 1974), therefore, trans-2-hexenal was considered to be not only the alarm pheromone component but also the aggregation pheromone component.

View full abstract

Different formulation of the synthetic female sex pheromone of Spodoptera littoralis were evaluated in the field. A trap baited with 1 mg of cis-9, trans-11-tetradecadienyl acetate (72% active isomer) alone adsorbed in a rubber septum was equivalent in effectiveness to a trap baited with virgin females for at least 77 days. The purified attractant (92% active isomer), however, was significantly less efficient in attractiveness than the partially purified synthetic attractant (72% active isomer). The addition of a small amount of cis-9, trans-12-tetradecadienyl acetate to the purified attractant strongly enhanced te attraction. However, cis-9, trans-12-tetradecadienyl acetate had no synergistic effect when added to the partially purified attractant. The addition of increased amounts of cis-9, trans-12-tetradecadienty acetate markedly reduced the cathch of male moths. The combination of 4.8-mg attractant (97% purity) with 12-mg antioxidant adsorbed on a filter paper was somewhat less efficient in attractiveness than virgin females.

View full abstract

The antifeedant of barnyard grass (var. oryzicola) against N. lugens was isolated and characterized as trans-aconitic acid. This acid was detected in barnyard grass but not in rice plant. Trans-aconitic acid, neutralized to pH 7 with calcium hydroxide, showed potent inhibitory activity for feeding of N. lugens at concentrations of 0.25% and 0.5% while the cis-isomer showed much less inhibitory activity.

View full abstract