The life cycle of some aphid species involves seasonal switches between unrelated summer (secondary) and winter (primary) host plants. Many of these “host-alternating” species, belonging to the sub-family Aphidinae, produce two return migrant forms on secondary host plants in autumn. Winged females (gynoparae) are produced first; these locate the primary host and deposit their sexual female offspring (oviparae). Later, males are produced on the secondary host and these locate the primary host independently before mating with the oviparae. The mechanisms of primary-host location by gynoparae and males are reviewed in this paper. Studies with several aphid species indicate that both forms are able to respond to volatile cues released by their specific primary host plant. Plant odours may also enhance or modify the responses of return migrants to the sex pheromone released by mature oviparae. Aphids are also able to sample non-volatile plant chemicals after landing, but there have been very few detailed investigations of the behaviour of return migrants at the primary-host-plant surface. Recent experiments with gynoparae of the black bean aphid, Aphis fabae Scopoli, show that these insects detect primary-host-specific cues during stylet penetration of peripheral plant tissues, and these stimuli promote settling and reproduction. Similar behavioural studies with males are required to shed light on the processes of speciation and reproductive isolation in host-alternating aphids.
A North American bruchid beetle Acanthoscelides pallidipennis (Motschulsky) was newly found on Kyushu Island, Japan, the larvae of which feed in seeds of introduced false indigo (or indigobush), Amorpha fruticosa L. (Fabaceae: Astragaleae). The morphological characters of the Japanese population were similar to those of introduced populations in Korea and China and of native populations in Texas. Plant quarantine records indicated that the introduction of A. pallidipennis was due to recent introductions of A. fruticosa seeds from China and/or Korea as soil cover on cut slopes. The proportions of seeds eaten by A. pallidipennis in three consecutive years (1997–1999) in Fukuoka, located in the northern part of Kyushu Island, were as high as 56.0% for the overwintered generation and 92.0% for the first generation feeding in the dry seeds of previous years. No parasitoid emergence was observed in the first two years. In 1999, however, Eupelmus sp. (Hymenoptera: Eupelmidae) had parasitized the overwintered generation at an extremely low level, which is the first record of a parasitoid of A. pallidipennis in Japan. Time lags required for parasitoids to use introduced phytophagous insects are reviewed. The ability of Eupelmus sp. and its host to overwinter and the short lag between our first observations of each of the two species in Japan may indicate a joint introduction of the parasitoid with its host.
The species composition of Liriomyza leafminers infesting commercially grown tomato plants was surveyed in two contiguous greenhouses in Muko City, Kyoto Prefecture, from August to December 1999. Full-grown larvae and puparia of Liriomyza were collected weekly from the greenhouses, and reared to adult emergence in the laboratory. The male adult flies that emerged were identified on the basis of the shape of their genitalia. The results revealed the occurrence of L. sativae, which has not been recorded in Japan. L. sativae coexisted with L. trifolii and L. bryoniae in one tomato greenhouse and with L. bryoniae in the other. Further, the relative abundance of the three species changed throughout the growing season of tomato plants and the peaks of each species population differed.
Cultural and morphological characters of isolates belonging to an entomogenous Paecilomyces species commonly found in Japan were investigated and compared with the literature. This species has not been recorded in major monographs of this genus, but identified as Paecilomyces cateniannulatus Liang described in 1981 from China. Mycelia on insects and media were pure white, and sometimes produce loose synnemata up to 10 mm. Growth rate of the fungus is moderate. The reverse side of colonies on SDY or MEA media are colorless to light yellow. Phialides are flask shaped with a narrow neck, 3.0–16.1×1.3–3.2 μm, often forming a whorl. Conidia are oval to short cylindrical, 2.1– 4.6×1.3–2.4 μm, arranged in basipital chains. Conidial chains are often irregularly curved and sometimes form a loop. Early stage of the conidiogenous structure of this fungus resembles that of Beauveria, but is distinguished by formation of conidial chains.
To compare the aedeagal length of sympatric species of Bactrocera fruit flies in Thailand, 340 specimens, which were collected with methyl eugenol traps from 7 localities, were examined. Based on aedeagal length and the costal marking at the apex of the wing, males were divided into 5 groups, i.e., a longer aedeagus with a continuous marking (LC, n=233), a longer aedeagus with a discontinuous marking (LD, n=2), a shorter aedeagus with a continuous marking (SC, n=7), a shorter aedeagus with a discontinuous marking (SD, n=97), and a very long aedeagus with a discontinuous marking (LLD, n=1). Using the CABIKEY (White and Hancock, 1997, Windows CD-ROM, CAB International, Wallingford), males of the LC and SD groups were determined to be B. dorsalis (Hendel) and B. correcta (Bezzi), respectively. The SC group was similar to B. dorsalis; however, all males of this group had a very narrow costal marking different from the typical B. dorsalis. The aedeagal lengths (without distiphallus) differed significantly among the 3 groups (ANCOVA, F=307.02, p<0.0001): the LC group (2.727±0.111 mm, mean±SD), the SC group (2.201±0.065 mm) and the SD group (2.063±0.075 mm). The aedeagal length of the LD group was 2.33–2.34 mm. This group resembled B. zonata (Saunders), however; they differed from the CABIKEY B. zonata in possessing a very small spot-like costal marking at the apex of the wing. The aedeagal length of one male of the LLD group was 4.17 mm. This male resembled B. tuberculata (Bezzi), but differed somewhat from the CABIKEY B. tuberculata. Thus, specimens of the SC, LD and LLD groups could not be accurately placed. The aedeagal length of B. dorsalis was compared with those of the parapatric species, B. papayae and B. carambolae, and potential factors affecting a longer and shorter aedeagal length are discussed.
This study investigated pheromone communication and mating behaviour of the coffee white stem borer (CWSB), Xylotrechus quadripes (Coleoptera: Cerambycidae), in South Yunan, China. Coupled gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometric (MS) analyses of volatiles released by male and female CWSB identified 2-hydroxy-3-decanone and 2,3-decanedione as male-specific candidate pheromones. Further GC-EAD and GC-MS analyses confirmed that only (S)-2-hydroxy-3-decanone is produced by male CWSB and elicits antennal responses by male and female CWSB. In field experiments, 2-hydroxy-3-decanone as a trap bait afforded capture of one female CWSB, and in laboratory experiments it weakly attracted female but not male CWSB. Complex mating behaviour in CWSB includes: 1) attraction of potential mates by both sexes; 2) repeated landings (with ever decreasing distance) of a female next to a male; 3) males dashing to a nearby female; 4) rejection of mating attempts by females; 5) post-mating female guarding by males; and 6) size-dependent mating success of males. Considering this complex mating behaviour, lack of direct flight towards pheromone sources, mating near pheromone-baited traps, and only moderate attractiveness of (synthetic) pheromone, pheromone-based trapping of females does not seem to be a viable strategy for managing CWSB populations in China.
Females of Bruchidius dorsalis, a wild bean weevil, exhibit courtship behavior actively, whereas the males are reluctant to mate but donate a large amount of seminal fluid, which eventually enhances female fecundity. This study examined the pre- and post-copulatory advantage of greater investing males: whether females choose greater investing males as their mates before copulation, and whether greater investing males attain larger reproductive success either by predominant sperm precedence or by prolonging the refractory period of the mating partner. B. dorsalis females did not preferably mate with greater investing or larger males, but refrained from mating for a longer period if they had obtained more investment. The sperm precedence of females mated with a sterilized and a normal male showed that the last mated male had precedence. Namely, B. dorsalis females did not choose greater investing males on a behavioral basis, but they preferentially used sperm of greater investing males by prolonging the mating interval according to the amount of the investment. The refractory period, approximately 20 h at the longest, was probably too short for the receiving females to assimilate the nutrients derived from the seminal fluid to the production of eggs that would be fertilized by the donating males. If this is the case, male investment in B. dorsalis is expressed as mating effort rather than paternal investment.
The oak platypodid beetle, Platypus quercivorus, stridulates both during premating behavior and when stressed, as well as spontaneously. When a female was put onto the bark surface of a male-infested log, she began to walk and produce an “approaching chirp, ” searching for a gallery entrance. When finding one, she entered it and tried to pull a male out. If the male's abdomen became visible, she appeared to push her frons against his elytral declivity and made a “premating buzz” that lasted about 5–10 s. During this buzzing, the male backed out of the gallery in order to allow her in. Females that had been silenced via surgery did not evoke this reaction; thus, males apparently identified females by their buzzing sound. The male then followed the female into the gallery, and produced an “in-gallery chirp” with his posterior abdomen visible. After a while, both sexes backed out of the hole and copulated at the entrance. Both sexes produced “stress chirps” when confined inside a cotton ball, and “spontaneous chirps” when walking alone on the surface of an oak bark piece.
Larvae of the Shonai ecotype of the rice stem borer, Chilo suppressalis, were in diapause until October when the ambient temperature was relatively high and most of the larvae terminated diapause in November before winter. The cold hardiness of field-collected larvae was low at the diapause stage, but relatively high at the post-diapause stage. Glycerol was scarcely detected at the diapause stage, but its content increased at the post-diapause stage. Conversion between glycogen and glycerol was found in diapausing larvae during temperature acclimation (0–30°C), but a time lag between glycogen loss and glycerol increase was detected under field conditions. The results obtained for the Shonai ecotype are compared with those of the other main ecotype of this species, the Saigoku ecotype.
To investigate factors involved in the recent northward invasion of the great mormon butterfly, Papilio memnon L. (Lepidoptera: Papilionidae), cold hardiness of pupae was compared among 4 populations including those in a subtropical and a northernmost area of Japan. The mean supercooling points (SCP) of diapausing and non-diapausing pupae were lower than −20°C in all populations. The SCP was not affected by an acclimation period nor by pupal weight, although it became higher with inoculation. Diapausing pupae were placed in 4 sites at different altitudes in southern Osaka Prefecture during the winter, then survival rates were compared in the spring. All individuals died at altitudes of 1, 100 and 800 m, while more than half of the individuals survived the winter at 400 and 30 m. There was no difference in the survival rate at each site among populations. Even the subtropical population showed cold hardiness to survive winter in Osaka, which is located near the northern edge of the distribution of this species. These results show that the recent northward invasion has occurred without any substantial changes in the cold hardiness of this species. Based on the results, we inferred that the climatic lethal limits during the winter lie between −3.8 and −7.3°C for the minimum temperature, and between 52 and 68 frost days. We discuss the effect of climatic warming on the northward invasion of this species.
Effects of methoprene (a juvenile hormone analog) on the larval development and hemolymph titers of biliverdin-binding proteins (BPs) in Spodoptera litura were studied. BP-A first appeared in the hemolymph of the fifth (penultimate) instar larvae, decreased during the molting to the sixth instar and prominently increased during the sixth (last) instar. On the other hand, the titer of BP-B, a predominant component in preceding stadia, greatly increased during the fifth instar, drastically decreased before the ecdysis to sixth instar, and slightly increased during the sixth (last) instar. Methoprene (0.1–5 μg/insect) topically applied on day 0 of the fifth instar caused little effect on the duration of the fifth instar and on the titers of BPs, while the application to day 0 sixth instars extended the last instar dose-dependently and changed the BP titers as follows: BP-A showed a similar increase as in untreated control, but continued to increase further during the prolonged feeding period; BP-B titer showed a increase within one day of the application. Double applications of methoprene at one day interval induced a stepwise increase of the BP-B titer at each application, but not of BP-A. These results suggest that BP-B synthesis is triggered by juvenile hormone, which also regulates the synthesis of BP-A indirectly by blocking larval-pupal transformation.
We observed color changes of the katydid, Conocephalus maculatus, from the hatchling to the adult stage under various rearing conditions using two populations in southern Osaka Prefecture. C. maculatus showed color polymorphism in the nymphal stage as well as in the adult stage: Although all the hatchlings were green irrespective of populations or conditions, the rate of green morph (G rate) decreased to 40–80% in the adult stage. Moreover, about 10% of individuals which had once turned brown returned to the green morph after one of the succeeding moults. The G rate of progenies between a green female and a green male tended to be higher than that between a brown female and a brown male throughout the nymphal stage, while environmental factors such as temperature, humidity and background color had no significant effect on nymphal color morph. The present results show that color-morph determination is controlled mainly by genetic factors and little affected by environmental factors in nymphs and adults of C. maculatus.
A clonal cell line (BCIRL-HZ-AM1-11) of Helicoverpa zea was grown in stationary and suspension cultures in Ex-Cell 401TM medium containing 10% fetal bovine serum at 28°C. The cell population doubling time was 22 h in stationary culture as compared with 27 h in suspension culture. A lag time of approximately 24 h was observed during the first 24 h of the suspension culture following initiation but no lag time was observed in the stationary culture. Maximum viral titers were achieved in stationary and suspension cultures at 120 h (1.80×106 TCID50/ml) and 168 h (1.48×107 TCID50/ml), respectively, following inoculation with the Helicoverpa zea baculovirus (HzSNPV/Br-CL2). Infected cells harvested at 168 h from the 50 ml suspension culture produced a total number of occlusion bodies of 3×109.
Population density of Plutella xylostella on two cabbage varieties (Kinkei 201 and Shinsei) in an urban environment created different pest loads. A maximum larval density of 9.3 larvae per plant was recorded in Kinkei 201 field. In contrast, the corresponding value was 6.3 larvae per plant in Shinsei field. Shinsei cabbage showed lower larval density of pest but higher parasitism by Cotesia plutellae. Four major parasitoids and two hyperparasitoids were collected and identified during the two year period. No egg parasitoids of the DBM were observed. Comparison of C. plutellae parasitism rates between the two varieties in the field showed a higher parasitism rate on Shinsei cabbage. Parasitoid density peaked on July 13 (4.1 cocoons/plant) in Shinsei and on June 27 (2.3 cocoons/plant) in Kinkei 201. Parasitism of host larvae by C. plutellae was high on Shinsei cabbage in both years and ranged from 40 to 83.3%. Pest density, parasitism rates and rain impact on Kinkei 201 and Shinsei are discussed.
The effects of three aphid species (fourth instars only), Aphis gossypii Glover; Myzus persicae (Sulzer) and Lipaphis erysimi (Kaltenbach), on immature development, survival and predation of the common green lacewing, Chrysoperla carnea (Stephens), were determined in the laboratory. Survival rates of C. carnea from first stadium to adult emergence were significantly different among larvae fed different aphid species. When larvae were fed A. gossypii and M. persicae, 94.4±3.3% (mean±SE) and 87.6±5.1% of individuals developed to adults, respectively; whereas only 14.9±3.4% of individuals developed to adults when fed L. erysimi. The developmental durations of C. carnea larvae were also significantly different among larvae fed the three aphid species. The developmental duration from first stadium to adult emergence was shortest when larvae were fed A. gossypii (19.8±0.4 d), followed by M. persicae (22.8±0.2 d), and then L. erysimi (25.5±0.4 d). The total number of fourth stadium aphids consumed by C. carnea larvae differed significantly among individuals fed different aphid species. Chrysoperla carnea consumed more A. gossypii (292.4) and M. persicae (272.6) than L. erysimi (146.4). Although total numbers of aphids consumed by the three C. carnea larval stadia differed significantly, the proportions of aphids consumed by each larval stadium to the total number of aphids consumed were similar, 3.9–7.1% by the first stadium, 12.0–16.8% by the second stadium, and 78.1–83.9% by the third stadium.
Second-, third-, early and late fourth-stadium larva, and pupa of Plutella xylostella (L.) were singly presented to female Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae) in the laboratory to investigate the effects of host age on oviposition behavior and development of the parasitoid. With regard to the oviposition behavior, the following three events were recognized after encountering the host: (1) drumming by antennae, (2) ovipositor penetration and oviposition, and (3) host feeding. Host acceptance rates did not differ among the different host ages except for pupa. Time required for ovipositor penetration and oviposition tended to increase with host age. About one third to one half of the wasps showed host feeding behavior irrespective of host age. The parasitism rate for fourth-stadium host larvae was higher than that for the second- and third-stadia. There were no significant differences among mean development times of the wasp in second-, third-, and early fourth-stadium larvae. However, development times in the late fourth-stadium hosts (=prepupa) were significantly shorter than in the early fourth- and other stadia hosts. This suggests that larval development of O. sokolowskii is influenced by host physiology.
The insecticidal activity of BT (Bacillus thuringiensis) formulations to the silkworm, Bombyx mori, reared under dark conditions was reduced significantly when the insects were reared under two different light conditions (80–120 and 1,500–2,000 lx: 16L–8D). The neonates reared with no illumination showed significantly lower sensitivity (20.7% mortality) than insects reared under the two illuminated conditions (50.3 and 52.1% mortality, respectively) (p>0.05). The LC50 of BT to insects reared under dark conditions (3.77 μg/g diet) was lower than for insects reared under the two light conditions (2.57 and 2.45 μg/g diet, respectively). These results strongly suggest that a protocol for rearing insects under dark will conditions reduce the insecticidal activity of BT formulations, and it is not appropriate to evaluate natural sensitivity to BT formulation of insects reared under dark conditions.
The cDNA fragments of a 2 kb gene, encoding the housefly acetylcholinesterase (AChE) were compared among 6 strains. While there were 4 substitutions of amino acids in the predicted peptides between Asp83 and Arg648, which is well conserved in insects, the following contrasts were made among the strains. The insecticide susceptible strains, aabys and SRS had Gly342 and Phe407, and the resistant strains, LPR, YBOL and YPRN had Ala342 and Tyr407, with Val342 unique to YBOL. In addition, Leu260 was found only in the chiral organophosphate resistant strains, YBOL and YPRN. These results showed that the patterns of single nucleotide polymorphisms, which resulted in amino acid substitutions, can be a practical tool for characterization of the insecticide resistance of houseflies.
Insecticidal bioassays on Plutella xylostella (Linneaus) of an oxadiazine insecticide indoxacarb and its N-decarbomethoxylated metabolite (DCJW), and their modulation of voltage-gated sodium channels in rat dorsal root ganglion neurons were examined. No significant difference was observed in insecticidal activity between indoxacarb and DCJW in ingestion and contact tests. In patch-clamp experiments, both indoxacarb and DCJW suppressed the peak sodium currents in a time- and dose-dependent manner. DCJW at 1 μM blocked the sodium currents to 62.7±3.0% (n=5) of the control after 25 min of bath application. In contrast, in the presence of 1 μM indoxacarb, currents were blocked to 4.5±0.6% (n=4) of control. Thus, the potency of DCJW in blocking sodium currents was higher than that of indoxacarb in rat dorsal root ganglion neurons.
Pot studies on the effects of mycorrhizal root colonization on plant growth and nematode reproduction in tomato-Meloidogyne incognita and carrot-Pratylenchus penetrans pathosystems were carried out. The mycorrhizal fungus Glomus mosseae did not protect tomato plants inoculated with the pathogen M. incognita when it was inoculated simultaneously with the mycorrhiza, as plants inoculated with M. incognita died before harvest. On the other hand, when tomato seedlings were inoculated with the nematode three weeks after mycorrhization, colonization of tomato roots by G. mosseae compensated for the reduction of plant growth caused by M. incognita infection. Tomato shoot weight was 24% greater and gall index 33% lower than plants inoculated with the nematode alone, and final soil densities of M. incognita were reduced by 85% when tomato roots were colonized by the mycorrhiza. Root infection by P. penetrans reduced carrot growth, but soil inoculation with Glomus sp. spores compensated for the damage caused by P. penetrans. Addition of Glomus spores to soil reduced P. penetrans soil densities by 49%.
The mate-receptivity behavior and reproductive capacity of single- and multiple-mated females of a predacious mite, Amblyseius womersleyi, were examined. Although most females rejected a second mating within one day after the first mating (1 day later), they accepted it towards the end of the oviposition period (10 days later). Females that had experienced full copulation twice produced significantly more eggs than those that had mated only once. All females that had copulated with a sterile male which had lost its ability to fertilize a female following a series of multiple matings, showed a positive response toward the second copulation on the next day. These results suggest that acquisition of sperm or seminal fluids is probably a critical factor for mating receptivity and that multiple matings are required in order to reach the full reproductive capacity for A. womersleyi females.