Post-diapause Adults Research Articles

Relationship between the natural duration of diapause and post-diapause reproduction in the cabbage beetle, Colaphellus bowringi (Coleoptera: Chrysomelidae)

The cabbage beetle, Colaphellus bowringi Baly undergoes an imaginal summer and winter diapause in the soil; adult emergence is spread over several months to more than 2 years, with prolonged diapause occurring in certain adults under natural conditions. The relationship between natural duration of diapause and postdiapause reproduction was investigated at 25°C under 12L: 12D photoperiod. The mean body weight of postdiapause adults with the long diapause duration of 21 months was significantly greater than with the shorter diapause duration of 5, 11 and 17 months. The longevity and mean total egg production of the postdia- pause adult females with the long diapause duration of 21 months was significantly greater than that of postdiapause females with shorter diapause duration of 5, 11 and 17 months. All results demonstrate that extended diapause is associated with a high level of postdiapause reproductive performance. There is no negative trade off between diapause duration and the post-diapause reproductive traits that we measured in C. bowringi.

Photoperiodic and Food Signals Control Expression Pattern of the Clock Gene, Period, in the Linden Bug, Pyrrhocoris apterus

The temporal expression pattern of the circadian clock gene period was compared between heads of the linden bug, Pyrrhocoris apterus , kept under diapause-promoting short days (SD) and diapause-preventing long days (LD) using a real-time PCR quantification. Diapause or reproduction was programmed by photoperiod during the larval stage, but the first difference in per mRNA abundance between SD and LD insects was observed only after adult ecdysis. The expression level of per mRNA was markedly higher, up to more than 10-fold, in the destined-to diapause animals compared with those scheduled for reproduction. Up-regulation of per transcript was restricted to an early diapause peak, with the maximum expression on days 3 to 5 after adult ecdysis. Starvation reduced the peak level of per mRNA to about 50% of the value found in feeding females in the SD conditions, but per mRNA abundance was similarly low in fasting and feeding females in LD. Photoperiodic refractoriness in either wild-type postdiapause adults or in a selected nondiapause variant of P. apterus was associated with reproduction and low, LD-like levels of per mRNA under both SD and LD. Overall, the data suggest that the photoperiodic programming itself has no direct effect on per mRNA abundance, but it does determine the response of per transcript to food signals during subsequent expression of diapause/reproduction physiology.

Parental effects: Physiological age, mating pattern, and diapause duration on diapause incidence of progeny in the cabbage beetle, Colaphellus bowringi Baly (Coleoptera: Chrysomelidae)

The cabbage beetle, Colaphellus bowringi Baly, is a short-day species that has both a facultative summer and winter adult diapause. In this study, we systematically investigated the effects of parental physiological age, mating pattern (including mating frequency and delayed mating), and diapause duration on the diapause incidence of progeny in the beetle. As parents aged, progeny diapause incidences showed considerable inter-parental variability and an abnormally varying pattern, but their predicting line was approximate to horizontal when reared under constant conditions. There was significant difference in progeny diapause incidence between multiple-mating and once-mating treatments. Higher diapause incidences in the progeny were observed in delayed-mating treatments. Progeny diapause incidences increased as diapause duration in the parental generation increased, and hibernating individuals produced more diapausing progeny than aestivating ones. Reciprocal cross tests between the post-diapause adults and non-diapause adults with no diapause history showed that the effect of parental diapause duration on the progeny diapause incidence was determined by both mothers and fathers but the mothers appeared to have a stronger effect than the fathers. Our results suggest that the parental age effect in Colaphellus bowringi might not be simply age-dependent, but may be controlled by the interaction of multiple factors, including physiological, environmental, behavioral and genetic factors. We discuss the ecological and physiological significance of these findings.

Effects of diapause duration on future reproduction in the cabbage beetle, Colaphellus bowringi: positive or negative?

Abstract. Cabbage beetles, Colaphellus bowringi, undergoing an imaginal summer and winter diapause in the soil, show a great difference in diapause duration (from several months to more than 3 years) under natural conditions. The effects of diapause duration on future reproduction in the beetle are investigated at 25 °C with an LD 14 : 10 h photoperiod and under natural conditions. The fecundity of postdiapause adults with a short diapause of 5 months and nondiapause adults is similar, showing that a short diapause has no affect on reproduction, whereas the longevity of postdiapause adults with a short diapause of 5 months is significantly shorter than nondiapause adults, showing that a short diapause has a negative affect on longevity. The mean total egg production per female and longevities of postdiapause adults with long diapause periods of 16, 22, 29 and 34 months are similar to nondiapause adults, but the mean daily egg production per female is significantly higher than nondiapause adults, showing that extended diapause has a positive effect on postdiapause reproduction. The offspring of postdiapause parents require a relatively shorter time for egg development compared with the offspring of nondiapause parents, showing that diapause has a positive effect on their offspring's performance. However, there are no significant differences among offspring performance in terms of survival, adult longevity, mean egg production per female and mean daily egg production per female.

Hormonal control of diapause and overwintering traits in a leaf beetle, Aulacophora nigripennis

Summary To elucidate whether Juvenile Hormone (JH) regulates physiological status in relation to diapause and cold hardiness, we investigated various physiological and biochemical changes in diapause adults of Aulacophora nigripennis after treatment with exogenous pyriproxyfen, an analogue of JH. Topical application of pyriproxyfen at high dose (≥0.05 μg) caused the diapause adults not only to consume more oxygen and mate earlier, but also to suppress enhancement of chill tolerance at 0°C and accumulation of myo-inositol. By contrast, a lower dose of pyriproxyfen (0.01 μg) did not, suggesting that the amount of pyriproxyfen between 0.01 and 0.05 μg is a critical dose breaking both diapause and cold hardening. Pyriproxyfen-treated post-diapause adults lost triacylglycerols, but not glycogen, more rapidly than the acetone control. It is suggested that triacylglycerols are the main energy resource in both diapause and post-diapause adults, but are consumed more by the latter because of their higher metabolic rate. Glycogen may be converted mainly into myo-inositol during diapause, but consumed as an energy fuel for basal metabolism during post-diapause development. Thus, various physiological and biochemical traits in relation to diapause and cold tolerance in this beetle may be at least in part under the control of JH.

Overwintering and Spring Migration in the BollwormHelicoverpa armigera(Lepidoptera: Noctuidae) in Israel

To clarify the relationship between overwintering and spring migration in the bollworm Helicoverpa armigera (Hubner) in Israel, we caged larvae under field conditions in fall and used sex pheromone traps to monitor field populations the following spring. No diapause was detected in October-exposed individuals. Overall, 67.7 and 89.2% of the individuals exposed to field conditions during November and December, respectively entered pupal diapause. Most nondiapausing individuals eclosed early in the following January. In contrast, postdiapause adults started to eclose synchronously in late April. Approximately 50% of the postdiapaused females eclosed before 6 May, 9 d before 50% of the males did. Capture of field H. armigera moths in sex pheromone traps occurred 1 mo before the eclosion of adults from caged overwintering diapause pupae. Moths trapped before the eclosion of diapausing individuals had lower wing loading, fewer wing scales, and larger relative thorax size (ratio of thorax to head widths). These morphometric data imply that the early season field moths were trapped after long distance flight. Taken together, the phenological and morphometrical data support the notion that H. armigera exhibits an early-spring migratory behavior in Israel. These results are discussed within the context of physiological and genetic data from related studies.

Larval diapause duration and fat metabolism in three geographical strains of the blow fly, Calliphora vicina

Diapausing larvae of the blow fly, Calliphora vicina, from three geographical strains exposed, as adults, to short days, were maintained under identical conditions (darkness, 11–12°C) and examined for changes in wet weight, dry weight, water and fat content during diapause development to the emergence of post-diapause adults. Larvae produced by flies originating from northern Finland (Nallikari, 65°N) showed a longer, more intense, diapause than those from localities further south (Edinburgh, Scotland, 55°N and Barga, Italy, 44°N), but all three strains showed similar rates of loss of the parameters measured. This was also the case for post-diapause adults, flies of the Barga strain with its relatively short diapause emerging with greater residual fat reserves than flies from the Edinburgh or Nallikari strains with their more protracted diapause. It was concluded that the rates of water and fat loss were functions of the conditions used for diapause larval maintenance (probably temperature) rather than the maternally programmed degree of diapause incidence, or of its ‘depth’ or ‘intensity’.

Establishment and Early Effects ofOmphalapion hookeri(Kirby) (Coleoptera: Apionidae) as a Biological Control Agent for Scentless Chamomile,Matricaria perforataMérat (Asteraceae)

Omphalapion hookeri(Kirby) (Coleoptera: Apionidae) (= Apion hookeriKirby) was released and established in four provinces in western Canada (British Columbia, Alberta, Saskatchewan, and Manitoba) as a biological control agent for scentless chamomile,Matricaria perforataMérat (Asteraceae), a rapidly spreading, introduced, annual weed of disturbed ground. Larvae of this univoltine European weevil feed on developing achenes in the capitula of scentless chamomile. Overall, 74% of releases resulted in establishment; these included both releases of prediapause adults in late summer or fall and postdiapause adults in early summer. In experimental plots in Alberta,O. hookeripersisted for five consecutive growing seasons from an initial release of 38 adults. Populations in these plots showed year-to-year increases of up to 17-fold, and in mass rearing cages net reproductive rates of up to 64-fold were obtained. Up to 17O. hookerideveloped in a single scentless chamomile seed head in the field. In the field plots each individual ofO. hookericompleting development reduced seed production in a head by 11.2 seeds; unattacked heads produced an average of 171 seeds. A host choice test confirmed thatO. hookeriwould not develop in the herbal chamomile,Chamomilla recutita.AdultO. hookeridispersed up to 350 m between emergence and oviposition. Our results suggest thatO. hookerican be established across the scentless chamomile-infested areas of the Canadian prairies and that it has potential for reducing the weed's reproductive output.

Seasonal change of the thermal response in relation to myo-inositol metabolism in adults of Aulacophora nigripennis (Coleoptera Chrysomelidae)

The thermal response of Aulacophora nigripennis adults in relation to myo-inositol metabolism changed seasonally. Myo-inositol accumulation was stimulated at 15 and 5°C in October (autumn), but only 5°C was effective for the accumulation in December (early winter). In February (mid winter), myo-inositol degradation was prominent at both temperatures. Myo-inositol metabolism of this beetle thus gradually shifts from synthesis to degradation as the season progresses. This may be related to the progress of diapause development and may contribute to the seasonal profile of the myo-inositol pool in a natural population. Post-diapause adults in March (spring) and June (early summer) regained the ability for myo-inositol accumulation at 5°C. Thus, there are at least two types of myo-inositol accumulation in this beetle; one is under the control of diapause and the other responds directly to environmental conditions independently of diapause.

Melatonin in the Testis of the Cabbage Armyworm, Mamestra brassicae

N-Acetyl-5-methoxytryptamine (melatonin; MEL) was detected in the testis of non-diapausing pupae and in the testis of post-diapause pharate adults of the cabbage armyworm, Mamestra brassicae, by use of a threedimensional HPLC system with multiple coulometric electrochemical detectors. Intermediates providing evidence of various metabolic pathways were identified, as follows: tryptophan (TRP) → 5-hydroxytryptophan (5-HTP) → 5-hydroxytryptamine (5-HT) → N-methyl-5-hydroxytryptamine (N-MET) ↳5-hydroxyindoleacetic acid (5-HIAA) ↳N-acetyl-5-hydroxytryptamine (N-ACET-5-HT) ↳melatonin (MEL). The possible physiological roles of melatonin in the testis of both diapausing and non-diapausing pupae are discussed.

Use of Imidacloprid- Treated Row Mixtures for Colorado Potato Beetle (Coleoptera: Chrysomelidae) Management

The ‘high dose’ strategy of applying imidacloprid as an ‘at-planting’ soil treatment uniformly throughout a potato field may result in rapid pest adaptation, as it has for other systemic insecticides. Alternatively, treated and untreated plants in a field provide a refuge to pests so that some portion of the population is not subjected to selection. In 1993- and 1994-field experiments involving potato cultivars with contrasting maturity periods, plots of mixtures of imidacloprid-treated and untreated rows were compared with plots of untreated and 100%treated rows to determine their effects on the Colorado potato beetle, Leptinotarsa decemlineata (Say). First-generation populations and feeding injury were significantly reduced by mixtures of imidacloprid treated rows, when post-diapause adults were released along the edge of plots to simulate a typical colonization pattern. Densities of life stages and percentage defoliation decreased as the proportion of imidacloprid-treated rows increased. The effectiveness of imidacloprid was greater than the additive effect based on the proportional contribution of the treated rows. Beetle populations decreased as the distance increased inward from the outer rows, because invading beetles were increasingly suppressed as they encountered rows of imidacloprid-treated plants. This suggests that the treated rows at the edge of the field in a row mixture acted as a toxic barrier to colonizing beetles. Even when colonizing adults were introduced uniformly in row mixture plots, the treated rows trapped many dispersing adults and suppressed feeding injury on adjacent untreated rows. Mixtures of treated and untreated rows deployed alone or in combination with a perimeter treatment are discussed as ways to reduce the amount and cost of insecticide used, create refuges to minimize resistance development, and reduce environmental risks.

Oviposition behaviour of post-diapause Hypolimnas bolina (L.) (Lepidoptera : Nymphalidae) in tropical Australia

Observations were made on the oviposition behaviour of post-diapause adults of Hypolimnas bolina (L.) at a site in Townsville, Australia (19˚15′S, 146˚45′E). Females most often laid one or two eggs on freshly emerged seedlings (<10 mm height) of Synedrella nodiflora (L.) (Asteraceae). Mature foodplants of S. nodiflora, Sida rhombifolia (L.), Sida acuta (Burm. f.) and Malvastrum coromandelianum (L.) (all Malvaceae) were present, and occasionally sampled by females, but were ignored as oviposition substrates. Females were present at the site from 0900 to 1500 hours, and were more persistent than their male counterparts under adverse environmental conditions (i.e. reduced temperature and solar radiation). The relatively high number and apparent selectiveness of ovipositing females in this situation indicates the importance placed on utilising fresh growth of the larval foodplant. This behaviour may serve to maximise the rate of return per unit reproductive effort of post-diapause females.

Seasonal Abundance and Parasitism of the Sunflower Beetle (Coleoptera: Chrysomelidae) on Cultivated Sunflower in the Northern Great Plains

Postdiapause adults of the sunflower beetle, Zygogramma exclamationis (F.), appeared in plots of sunflower, Helianthus annuus L., between 28 May and 9 June and were present until mid-July 1985-1987. Peak density of adults occurred between 13 and 23 june when plants had 6-15 leaves. Eggs were present on plants for approximately 1 mo (June) with maximum egg densities occurring between 13 and 26 June. Larvae were initially observed between 10 and 19 June when plants had 5-12 leaves and were present an average of 53 d before entering the soil to pupate. There were four larval instars. New-generation (prediapause) adults emerged from the soil at the end of july or the beginning of August. By late September, all prediapause adults had left the plants and entered the soil to overwinter. Although population densities varied, life history patterns were similar among the 3 yr. There was one generation per year. The parasitoid Erixestus winnemana Crawford (Hymenoptera: Pteromalidae) was reared from sunflower beetle eggs, but egg parasitism was extremely low (1985, 0.1%; 1986, 1.9%; 1987, 0.4%). Doryphorophaga macella Reinhard (Diptera: Tachinidae) was the only larval parasitoid recovered. Larval parasitization varied between 0 and 14.8% in 1985, 35.7 and 66.7% in 1986, and 0 and 100% in 1987. The life history of D. macella showed good synchrony with its host; sunflower beetle larvae were parasitized during the entire period they were present. The tachinid parasitoid Myiopharus sp. was recovered from prediapause adult sunflower beetles in 1987, but its rate of parasitization was only 1.7%. Parasitism by D. macella may have contributed to the reduction in sunflower field infestations by the sunflower beetle during recent years.

Photoperiodic induction of the first and the second diapause in the bean bug, Riptortus clavatus: a photoperiodic history effect

In nondiapause adults raised under a long-day photoperiod, the critical daylength for diapause induction was between 13 and 14 h although some individuals did not respond to the short-day photoperiod and went on laying eggs. In postdiapause adults in which LD 13∶11 induced the first diapause (L13 insects), the critical daylength for diapause reinduction was between 13 and 14 h, whereas it was between 12 and 13 h in postdiapause adults in which LD 10∶14 induced the first diapause (L10 insects). Under LD 13∶11, a small proportion of L10 insects went into the second diapause after great delay as compared with L13 insects. Under LD 10∶14, on the other hand, L10 insects went into the second diapause more rapidly than L13 insects. Therefore, the photoperiod which had induced the first diapause affected the photoperiodic induction of the second diapause not only in the critical daylength but also in the speed of response. In Riptortus clavatus, the photoperiodic history influences the subsequent photoperiodic response even after a physiological state induced by the previous photoperiod was terminated completely.

INTERACTIONS OF THE AMBROSIA BEETLE, XYLEBORUS DISPAR (COLEOPTERA: SCOLYTIDAE), WITH ITS SYMBIOTIC FUNGUS AMBROSIELLA HARTIGII (FUNGI IMPERFECTI)

AbstractTwo bioassays were used to study the effects of the various life stages of a Temperate Zone ambrosia beetle, Xyleborus dispar (F.) (Coleoptera: Scolytidae), on the induction of the ambrosial form of its symbiotic fungus, Ambrosiella hartigii Batra (Fungi Imperfecti).Postdiapause adults and pupae of X. dispar cause a change from the mycelial to the ambrosial form of A. hartigii in culture.Larvae feed on the mycelial form in vitro, but ambrosia is required by larvae to develop and pupate. One of the main factors inducing the ambrosial form of A. hartigii is probably a secretory product of X. dispar.

In Vitro Culture of the Ambrosia Beetle Xyleborus dispar (Coleoptera: Scolytidae) with its Symbiotic Fungus, Ambrosiella hartigii1,2

Postdiapause adults of the ambrosia beetle Xyleborus dispar (F.) collected in March through June with rotary nets, and excised from overwintered and newly attacked host material, produced a single generation when the beetle was reared in vitro with its symbiotic fungus, Ambrosiella hartigii Batra. Prediapause beetles excised from host material in September failed to oviposit. This report is the 1st record of rearing a temperate zone scolytid on a fungus in the genus Ambrosiella.