Duration Of Oviposition Research Articles

蝇蛹金小蜂的交配行为及雄蜂交配次数对雌蜂繁殖的影响

多数昆虫能够进行多次交配,随寄生蜂雄蜂交配次数的增加,雄蜂体内精子减少,雌蜂获得的精子数量减少,产下更多的单倍体卵,发育为雄性后代;一些单寄生性的寄生蜂雌蜂一生仅能够交配1次。描述了蝇蛹金小蜂雌雄蜂的交配行为,探讨了雄蜂交配次数对雌蜂后代产量等的影响以及雌蜂的可交配次数。结果表明,交配过程包括求偶、交尾前期、交尾和交尾后期;雄蜂已交配的次数并不能够显著影响其配偶的寿命、产卵期和后代总数量,但显著影响到其配偶的雌、雄后代数量和性比。随雄蜂交配次数的增加,与之交配的雌蜂的后代雄性百分比显著增大,雌蜂在产卵期内更早地出现较多雄性后代,体内精子不足的现象更加明显。无论已交配的蝇蛹金小蜂雌蜂在产卵期中是否出现精子不足,均不能再次完成交配。;Most insects can mate multiple times. With the increasing of male mating frequency, male parasitoid wasps would have less sperm, and the female partners would gain less sperm during copulation, which will make them lay more unfertilized eggs, developing into male offspring. Some solitary female parasitoid wasps can only mate once in the life span. In this article, the mating behavior of the solitary endoparasitoid, <em>Pachycrepoideus vindemmiae</em> Rondani, was described, with the pupae of houseflies as the hosts, and the effects of male mating frequency on the production of the female partners and the possible mating times of the mated females were studied. The results showed that the mating behavior of <em>P. vindemmiae</em> included courtship, precopulatory, copulation, and postcopulatory, which lasts (41.21±83.16) s, (26.05±17.99) s, (2.62±0.62) s, and (30.43±11.44) s, respectively. When mated with males for the 1^st, 3^rd, 6^th, 9^th, 12^th, and 15^th times, the longevity of the females was (11.18±7.17) d, (10.82±8.51) d, (9.09±5.74) d, (9.36±4.74) d, (9.64±3.47) d, and (13.45±7.03) d, respectively, and the oviposition duration was (9.73±7.52) d, (9.82±8.51) d, (7.55±5.20) d, (8.18±4.71) d, (8.55±3.50) d, and (11.64±7.50) d, respectively. The total progeny number was (57.00±39.15), (50.18±35.52), (44.18±24.62), (42.55±15.69), (47.27±18.23), and (62.09±37.55), respectively, and the male proportion was (0.21±0.19), (0.17±0.06), (0.27±0.22), (0.43±0.31), (0.45±0.30), and (0.63±0.34), respectively. The mating frequency of males did not significantly affected longevity, oviposition duration and total progeny number of the female partners, but significantly affected the production of female and male progeny and offspring sex ratio, respectively. With the increasing of male mating times and with the increasing of female oviposition duration, daily female offspring number per foundress decreased, but male offspring number increased. When males mated for the 1^st, 3^rd, 6^th, 9^th, 12^th, and 15^th times, females laid offspring with male proportions higher than 50% on the 8^th, 17^th, 11^th, 6^th, 5^th, 2^nd day, respectively. The interaction of female ages and mating frequency affected offspring sex ratio significantly. After mated with the males which had mated multiple times, females laid more male offspring earlier, which suggests the sperm limitation in females was more obviously when they had mated with multiply mated males. Mated females could not finish mating again neither just after mating nor after they had laid eggs for 8 days, which suggests females might mate only once in their life span, no matter whether they lack sperm or not.

Oviposition behaviour ofSympetrum frequens(Selys) (Odonata: Libellulidae)

Oviposition behaviour by Sympetrum frequens, a species endemic to Japan, has been observed throughout its entire breeding season, which extended for about one month after the harvest of rice. Approximately 50% of oviposition events occurred during the first week of the reproduction period. Sunny oviposition sites were preferentially selected by ovipositing pairs. The starting time of oviposition was highly correlated with the ambient temperature (Ta), the days elapsed since the beginning of the oviposition period, and the weather of the day. The mean duration of oviposition (DO) was 325.0±194.7 s in tandem oviposition (TO) and 152.5±101.8 s in oviposition of the female alone (single oviposition; SO), and DO was poorly correlated with Ta. Dip rate (DR) was constant throughout the oviposition bout; however, wing-stroke frequency (WSF) of the tandem male declined from the start of oviposition to its end. The WSF of males in TO was 39.4±2.8 Hz, significantly higher than that of tandem females (34.5±3.0 Hz, p<...

Behavioral Interactions betweenBemisia tabaci(Homoptera: Aleyrodidae) andTetranychus truncatus(Acarina: Tetranychidae)

Interspecific interactions between Bemisia tabaci (Gennadius) and the spidermite Tetranychus truncatus Ehara were evaluated by observation of behavioral responses over 30 min intervals on cowpea leaves. The response of adult female whiteflies was observed on 4 classes of leaf: (1) uninfested (2) previously fed upon by spidermite nymphs, (3) spidermite nymphs and webbing present, and (4) spidermite adults present. Likewise, adult female spidermite response was observed on (1) leaves uninfested with whiteflies, (2) leaves previously fed upon by whitefly nymphs, (3) leaves with whitefly nymphs present, and (4) leaves with whitefly adults present. Spidermites generally had a greater effect on whitefly behavior than vice versa. Whitefly feeding duration decreased while labial tapping duration and frequency increased on all 3 types of mite-infested leaves compared to uninfested leaves. Although whitefly oviposition duration and frequency did not change on leaves infested with spidermite nymphs, whitefly fecundity decreased compared to untreated leaves. Although whitefly effects on spidermite behavior were less marked, nevertheless, duration and frequency of cheliceral tapping by spidermites did increase in the presence of whiteflies, although duration or frequency of feeding did not. Thus, one would predict that spidermites would win out in competition with whiteflies on a common host plant. Behavioral observations of interactions between herbivores can provide valuable insight into competitive relationships which should, however, be verified by field studies.

English

Some morphological and biological features of Megacephala euphratica euphratica were examined. The life table of M. euphratica euphratica was investigated and the net reproduction rate (R 0), length of generation (T 0) and rate of natural increase (r m) were calculated in 2004 under labarotory conditions. The net reproduction rate (R 0) of M. euphratica euphratica (6.02), representing the total fe- male birth rate with a mean length of generation (T0) as 18.87 days, was determined, and the intrinsic rate of natural increase (r m) was calculated as 0.0981. The duration of pre-oviposition, oviposition and post-oviposition of the species, the shortest life span of both male and female, and the lowest and highest total eggs of female were also investigated. Some morphological features, like adult descrip- tion and body size of the species, collected from Izmir, Mersin and Adana provinces, in 2001 and 2010, was given.

Effect of long-term exposure to simulated acid rain on the development and reproduction of the predatory mite, Euseius nicholsi (Ehara et Lee) (Acari: Phytoseiidae)

The effects of simulated acid rain on the development and reproduction of E. nicholsi, an important natural enemy of many species of pest mites in China, were studied in the laboratory. The life history parameters of E. nicholsi were investigated after long-term (about 8 generations) exposure to various levels of simulated acid rain (pH 2.0, 3.0, 4.0, and 5.6). The results showed that the acid rain had negative effects on some basic parameters of the life history of the E. nicholsi population indirectly. The whole development durations with pH 3.0–5.6 treatments were longer and the duration with pH 2.0 treatment was shorter than with deionized water treatments (control). Adult longevity and oviposition duration were notably shortened, and female fecundity was decreased by an increase in acidity. The net reproductive rate (R0) of the populations treated with acid rain was less than that of the control populations and gradually decreased with an increase in acidity; however, the values of the intrinsic rate of increase (r) were not affected significantly by acid rain, and inhibitory effects of acid rain on the population growth of E. nicholsi were not recognized.

Fertilisation and prey deprivation affecting reproduction, life history and life table of the predacious mite Paraseiulus talbii (Athias-Henriot) (Acari: Phytoseiidae)

Two factors were examined to determine their effect on the life history, reproduction and life table parameters in the predacious mite Paraseiulus talbii (Athias-Henriot), cultured in the laboratory at 32°C and 75% RH, using tydeid mite, Orthotydeus californicus (Banks) as food. The factors investigated included age of mating females and food deprivation periods during adult stage. Age of mating females has an influence on fecundity and adult longevity; old females decreased egg production and shortened adult longevity compared with young females under constant conditions of abundant prey. A significant lower fecundity, shorter oviposition period and adult longevity were recorded on females when exposed to different food deprivation programmes. Old mating females (30-days old) as well as females exposed to severe food deprivation (three days starvation/a week) resulted in the lower net reproductive rate (Ro), intrinsic rate of natural increase (rm) and finite rate of increase (λ) values (Ro = 7.301 and 7.486, rm = 0.202 and 0.198, λ = 1.224 and 1.219) compared with young females (0-day old) and without food deprivation (Ro = 41.312, rm = 0.308, λ = 1.361). The influence of the duration of copulation on egg production was also studied. Artificial curtailment of copulation to half or quarter the average duration resulted in a reduction in the percentage of reproducing females, fecundity, oviposition duration and the proportion of females in the progeny.

Heat Requirements for the Development of the Black cutworm, Agrotis ipsilon (Hüfnagel) (Noctuidae: Lepidoptera)

The present investigation aimed to study the effect of three constant temperatures (20, 25, and 30°C) on the development of the black cutworm, Agrotis ipsilon (Hufnagel). The incubation period, larval duration, pupal duration, pre oviposition period and duration of generation were estimated. The time required for development was decreased as the temperature increased from 20 to30 °C. The lower threshold temperatures (t0) was 11.49°C for eggs, 10.63 °C for larvae, 9.83 °C for pupae, 11.06 °C for pre-oviposition period and 10.53 °C for generation. The average thermal requirements needed for completing the development were 51.3, 303.5, 183.5, 38.1 and 575.3 degree-days for eggs, larvae, pupae, pre-oviposition period and generation, respectively.

Seasonal variation in genital and body size, sperm displacement ability, female mating rate, and male harassment in two calopterygid damselflies (Odonata: Calopterygidae)

Sperm competition is a pervasive force. One adaptation is the male ability to displace the rivals' sperm that females have stored from previous copulations. In the damselfly, Calopteryx haemorrhoidalis asturica, males with wider aedeagi displace more spermathecal sperm. The present study documents that the same mechanism operates in another damselfly, Hetaerina americana. However, this genital width in both species decreases along the season, but late-emerging females have more sperm displaced than early-emerging females. Because territorial males mated more and were larger in body and genital size than nonterritorial males, late-season females mated with considerably larger males with respect to female size and this produced higher sperm displacement. Assuming female benefits from storing sperm but that such benefit does not prevail if males displace sperm, it is predicted that, along the season, females will mate less and male harassment (in terms of male mating attempts and oviposition duration) will increase. These predictions were corroborated. In H. americana, it was also tested whether spermathecal sperm became less viable along the season. The results obtained did not corroborate this. This is the first evidence indicating that season affects sperm displacement ability and female mating frequency due to changes in male body and genital size. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 815–829.

Field and laboratory studies in a Neotropical population of the spinose ear tick,Otobius megnini

One ear of each of five cows on a property close to Dean Funes, province of Córdoba, Argentina, was inspected monthly from December 2004 to November 2006 to determine the presence of Otobius megnini (Dugès) and to ascertain its seasonality. Ticks were collected to study the biological parameters of larvae, nymphs and adult ticks. Groups of nymphs were also maintained at three different photoperiods at 25 degrees C. The abundance of immature stages was greatest during January-April and August-October in the first and second years of the study, respectively. No larvae successfully moulted. Nymphs weighing < 17 mg also failed to moult, but 89% of heavier nymphs moulted into adults. Nymphs moulting to males weighed less (49.5 +/- 16.09 mg) than nymphs moulting to females (98.1 +/- 34.08 mg). The pre-moult period was similar for nymphs moulting to either sex and significantly longer (P < 0.01) for female nymphs maintained at 25 degrees C compared with nymphs kept at 27 degrees C. No effect of photoperiod on the pre-moult periods of nymphs was detected. Female ticks produced a mean of 7.0 +/- 1.94 egg batches after a preoviposition period of 16.4 +/- 8.41 days for the first batch. The mean oviposition period was 61 +/- 20.8 days and the duration of oviposition for each batch varied from 1 to 6 days. The mean number of eggs per batch was 93.1 +/- 87.53. The minimum incubation period for the first egg batch was 13.6 +/- 2.77 days. The total number of eggs laid by each female was 651.6 +/- 288.90. Parthenogenesis was not observed. The reproductive efficiency index (REI) (number of eggs laid/weight of female in mg) was 5.5 +/- 1.26. Pearson's correlations showed a significant direct relationship between the weight of the female and number of eggs laid (P < 0.01) and REI (P < 0.05). Several of the biological values presented above for the tick population from the Neotropical zoogeographic region showed marked differences to equivalent values for O. megnini populations from the U.S.A. (Nearctic) and India (Oriental). Nevertheless, the only two sequences of 16S rDNA deposited in GenBank from ticks originating in Argentina and allegedly in the U.S.A. indicate that they are conspecific (99.8% agreement). We tentatively consider the biological differences among populations of this tick species to represent adaptations for survival at different conditions.

Influence of long-term exposure to simulated acid rain on development, reproduction and acaricide susceptibility of the carmine spider mite, Tetranychus cinnabarinus.

Development, reproduction and acaricide susceptibility of Tetranychus cinnabarinus (Boisduvals) (Acari: Tetranychidae) were investigated after long-term (about 40 generations) exposure to various levels of acid rain; pH 2.5, 3.0, 4.0, and 5.6. Deionized water (pH 6.8) served as a control. The mites were reared on eggplant leaves at 28°C, 80%RH and a photoperiod of 14:10 (L:D) in the laboratory. The results showed that the duration of the immature stage was significantly affected by acid rain exposure. The shortest duration (8.90 days) was recorded for populations exposed to pH 5.6 acid rain, while the longest duration (9.37 days) occurred after exposure to pH 2.5 acid rain. Compared with the control population, adult longevity was shortened with an increase in acidity. Similarly, the oviposition duration was also shortened by an increase in acidity. Statistically, female fecundity did not differ significantly between pH 5.6, pH 4.0 and control populations, but did differ significantly between the control population and those exposed to pH 2.5 and pH 3.0 acid rain. This suggested that the mite suffered reproductive defects after long-term exposure to acid rain with higher acidity (pH 2.5 and 3.0). The intrinsic rate of increase among different populations was not significantly affected, but the net reproductive rate of populations exposed to pH 2.5 and 3.0 acid rain was significantly less than pH4.0, 5.6, and control populations. Bioassay results showed that after long-term exposure to acid rain, susceptibility of the mites to two acaricides, dichlorvos and fenpropathrin, did not change significantly.

TAXONOMIC VARIATION IN OVIPOSITION BY TAILED FROGS (ASCAPHUS SPP)

Abstract Tailed frogs (Ascaphus spp.) oviposit in cryptic locations in streams of the Pacific Northwest and Rocky Mountains. This aspect of their life history has restricted our understanding of their reproductive ecology. The recent split of A. montanus in the Rocky Mountains from A. truei was based on molecular differentiation, and comparisons of their ecology are limited. Our objectives were to provide a range-wide summary of information on Ascaphus oviposition, compare some aspects of the reproductive ecology of the 2 species, and examine geographic variation in their reproductive traits. Reproductive ecology of the 2 species differed. Ascaphus truei had smaller clutches, oviposited later in the summer, and had a longer duration of oviposition than A. montanus. A greater number of communal oviposition sites were attributed to A. montanus. These ecological differences support the recent taxonomic revision of Ascaphus and suggest that different management strategies may be necessary for each species whe...

Effects of male harassment on females' oviposition behaviour in Libellulidae (Odonata)

Abstract I investigated whether the level of male harassment affects females’ ovipositionbehaviour, such that females oviposit unguarded under suboptimal conditionsand/or vary oviposition duration, dip number, dip frequency or number of oviposi-tion site changes. The study species were the libellulids Crocothemis erythraea , Orthetrum chrysostigma , Pantala flavescens , Sympetrum fonscolombii , Trithemisannulata and T. kirbyi ardens . Only a few ovipositions under suboptimal conditionswere observed and females hovered lower under high male harassment. However,in only a few species studied oviposition behaviour differed with the level ofharassment. No evidence for a special female strategy to avoid the negative effectsof males’ harassment was found. Due to the great intraspecific variability females seemed to be able to react flexibly to current conditions, such as changing maledensity and the level of male harassment. Introduction Density has an important influence on the behaviour of mature male libellulids atreproduction sites (Pezalla 1979). High density intensifies male-male competitionso that males have a lower chance to mate and face higher costs due to fights(Corbet 1999: 375). For males, several behavioural parameters are known to changeunder high densities, for example: (1) a reduction in territorial size (Alcock 1998),(2) a decreasing duration of territorial occupancy (Sherman 1983), (3) shortercourtship (Martens 1996), (4) shorter (Miller 1982) or longer (Rehfeldt 1989) co-pulation, and (5) increased aggressive behaviour in some species (Pajunen 1966;Wolf & Waltz 1984; Corbet 1999: 657). As most of the literature on odonate mating patterns has focused on males, whilefemales were often ignored or just considered as passive partners (Fincke et al.1997), less is known about possible effects of multiple mating and male harassmentduring oviposition under high male density on females. Multiple mating causesbenefits and costs for females. Whereas males can increase their reproductive success

Detection and Avoidance of Fish Predators by Adult Enallagma Damselflies

Reproductive success of iteroparous insects depends on their own survival as well as that of their offspring and thus adults should consider risk of predation to both themselves and their offspring when selecting a suitable place to lay eggs. We surveyed species composition of Enallagma damselflies from sites in eastern Ontario and found that, similar to studies in Michigan, USA, Enallagma boreale does not co-exist with fish, whereas E. signatum is apparently restricted to sites with fish. E. ebrium is found at fish and fishless sites. Laboratory experiments on these species showed no effect of chemical cues of fish presence on propensity to oviposit or number of eggs released. By using field enclosures, we found adult E. ebrium could detect and avoid fish during visits to a site, but females visiting fish sites did not significantly reduce oviposition duration.

Do behavioural and life-history traits vary with mate-guarding intensity in libellulid odonates?

It has been demonstrated that in libellulid dragonflies the distribution of eggs during oviposition and the offspring size vary with the type of mate guarding during oviposition (non-contact guarding and contact guarding). In this study, we investigated the hypothesis that oviposition behaviour and life-history traits also differ between these two guarding types. Therefore, we studied oviposition behaviour and life-history traits in six species of a dragonfly assemblage of the Namib Desert. Among the oviposition behaviours, oviposition duration and number of pond changes differed significantly between the guarding types. Clutch size did not differ between the guarding types, whereas some offspring characters, namely egg width, temperature sum to hatch, and larval head width, differed between the guarding types. Eggs of tandem species (those performing contact guarding) were larger, which might explain differences in all other offspring characters studied; bigger eggs need a lower temperature sum for egg development, result in bigger larvae, and have a faster growth rate, all traits that might be seen as an adapation to temporary waters, which are major habitats of the tandem species. This observation is discussed in the light of different dispersal strategies between the species performing different guarding types.

Oviposition behavior of Zabrotes subfasciatus females (Coleoptera, Bruchidae) under conditions of host deprivation

Oviposition of Zabrotes subfasciatus (Boheman, 1833) on Phaseolus vulgaris (Linnaeus, 1753) was studied immediately after emergence of the adults throughout the females life and in situations of host deprivation lasting for 1 to 10 days. The number of eggs laid daily, longevity, duration of oviposition and distribution of eggs per grain were studied. The number of eggs laid per day varied significantly, with the oviposition peak in the presence of the host (control group) occurring between day 2 and day 5 of oviposition. In the absence of the host, a shift in the oviposition peak to the first day after deprivation was observed, except for the group deprived for one day which showed a peak between days 1 and 4 after introduction of the host. The distribution of the eggs per grain in the control group and in the groups deprived of the host for 2, 5, 8 and 10 days, a larger egg aggregation was observed for all deprived groups compared to the control group.

Egg distribution, mate-guarding intensity and offspring characteristics in dragonflies (Odonata)

We studied how egg size, larval size and egg development time are related to oviposition site selection and mate guarding in a dragonfly assemblage of the Namib desert. Species that oviposited mainly in tandem flight (Pantala flavescens and Sympetrum fonscolombii) spread their eggs over several ponds, which we interpreted as spatial risk spreading. Other species (Orthetrum chrysostigma, Trithemis kirbyi, T. annulata and Crocothemis erythraea) performed noncontact guarding and localized their eggs, usually in a single pond, which we interpreted as distinct habitat selection. Because long oviposition durations increase the risk of disruption by rival males, we predicted that in species that localize their eggs to a distinct oviposition habitat the first-laid eggs of a clutch should be the largest, indicating high quality. Species that perform risk spreading should distribute large eggs randomly over all oviposition sites. We tested our hypothesis at artificial ponds using experimental manipulations of oviposition. In O. chrysostigma and T. kirbyi, egg size and larval size decreased significantly with order of laying, and the time to hatch was randomly distributed. As predicted, within the clutches of P. flavescens and S. fonscolombii, egg size was randomly distributed over a clutch and we found no trend of decrease in larval size or increase in the time to hatch in relation to order of laying.

Individual production differences do not explain cannibalistic behaviour in laying hens

1. Sixty-three laying hens were collected from 5 commercial farms experiencing outbreaks of cannibalism. It is known that cannibalistic behaviour varies strongly between hybrids and between individuals of the same hybrid. The aim of this study was to test specific hypotheses about the causation of cannibalism by comparing matched individuals varying in their cannibalistic behaviour. 2. To investigate feed efficiency, egg production and feed consumption, data were collected over 30 d. Nutrient deficiencies have been associated with outbreaks of cannibalism and we hypothesised that cannibals are more feed efficient than their flock mates and, therefore, more susceptible to transient nutrient deficiencies or imbalances that trigger cannibalistic behaviour. 3. Video recordings were made of victims of cloacal cannibalism and their matched controls during oviposition. Victims were expected to have longer oviposition durations and a higher incidence of short-term cloacal prolapses than controls, because the starting point for cannibalism is often suggested to be pecking at the red mucosa of the victim during, or just after, oviposition. 4. Oviduct swab samples were taken from surviving victims of cloacal cannibalism and their matched controls 4 weeks after the cannibalistic attack. If peck wounds provide a route for subsequent bacterial invasion of the reproductive tract, victims would be expected to have greater bacterial colonisation of the oviduct. 5. Mortality within each matched trio was recorded over a 23-month period after the cannibalistic attack. Victims that survived a cannibalistic attack were expected to have reduced longevity compared to controls and cannibals. This could occur if they developed secondary infections as a result of the cannibalistic attack, or if they had poorer health even before the attack. 6. No significant differences were found between cannibals, victims and controls in feed efficiency or any of the production variables measured. Victims of cloacal cannibalism did not expose their cloacal mucosa more, or for longer, than matched control hens during oviposition, and had no more bacteria in their oviduct. Victims tended to die sooner than their matched cannibals or cannibals during a 23-month period after a cannibalistic attack.

Microclimate influence in a physiological model of cattle-fever tick ( Boophilus spp.) population dynamics

Since their official eradication from the US in 1943, the cattle-tick species Boophilus microplus and Boophilus annulatus, vectors of bovine babesiosis, frequently have penetrated a quarantine zone established along the Texas–Mexico border designed to exclude them. Inspection and quarantine procedures have eradicated reinfestations successfully within the US, but increasing acaricide resistance in Mexican B. microplus populations poses a threat to future eradication efforts. Better understanding of interrelationships among Boophilus populations, their hosts, and vegetation communities in south Texas could improve prediction of the behavior of reintroduced Boophilus populations and increase management options. To this end, we constructed a simulation model to evaluate how microclimate, habitat (i.e. vegetation) heterogeneity, and within-pasture cattle movement may influence dynamics of Boophilus ticks in south Texas. Unlike previous Boophilus tick models, this model simulates dynamics at an hourly time-step, calculates all off-host dynamics as functions of temperature and relative humidity, and runs with ground-level microclimate data collected bi-hourly in three different habitat types. Sensitivity analysis of the model showed that temperatures and relative humidities created by habitat type, as well as engorged female mass, influenced tick population dynamics most strongly. Host habitat selection, initial number of larvae per cow, and the number of cells into which the simulated pasture was divided also had a strong influence. Population dynamics appeared moderately sensitive to the proportion of Bos indicus in cattle genotypes and the larval attachment rate, while appearing relatively insensitive to factors such as mortality rate of engorged females. When used to simulate laboratory experiments from the literature, the model predicted most observed life-history characteristics fairly well; however, it tended to underestimate oviposition duration, incubation duration, and egg mortality and overestimate larval longevity, especially at low temperatures and high humidities. Use of the model to predict Boophilus population dynamics in hypothetical south Texas pastures showed that it reasonably generated qualitative patterns of stage-wise abundances but tended to overestimate on-host tick burdens. Collection and incorporation of data that appear not to exist for Boophilus ticks, such as larval lipid content and lipid-use rates, may improve model accuracy. Though this model needs refinements such as a smaller spatial resolution, it provides insight into responses of B. microplus or B. annulatus populations to specific weather patterns, habitat heterogeneity, and host movement.

Effects of greenhouse pesticides on the soil-dwelling predatory mite Stratiolaelaps scimitus (Acari: Mesostigmata: Laelapidae) under laboratory conditions.

Knowledge of the effects of pesticides on biological control agents is required for the successful implementation of integrated pest management (IPM) programs in greenhouse production systems. Laboratory assays were conducted to assess the effects of an acaricide (dicofol), two insecticides (chlorpyrifos and pyriproxyfen), and two fungicides (fosetyl-Al and mefenoxam) on Stratiolaelaps scimitus (Womersley), a soil-dwelling predatory mite widely marketed in North America under the name Hypoaspis miles (Berlese) as a biological control agent of dark-winged fungus gnats (Bradysia spp.). Eggs, larvae, protonymphs, deutonymphs, and adult male and female mites were first assayed using dicofol, an acaricide used in the experiments as a positive control, applied to filter paper in an enclosed arena. Protonymphs were assayed for lethal and sublethal effects against the remaining pesticides at maximum label-recommended rates applied to filter paper, by using dicofol as a positive control and water as a negative control. The larva and protonymph were the life stages most susceptible to dicofol, with estimated 24-h LC50 values of 9 and 26 mg m(-2), respectively. Chlorpyrifos was highly toxic to the protonymphs of S. scimitus, causing >95% mortality after 24-h exposure and 100% mortality after 48 h. In contrast, the insect growth regulator (IGR) pyriproxyfen was much less toxic to protonymphs of S. scimitus; pyriproxyfen caused no significant mortality, compared with <5% mortality in the water control. Mortality caused by the fungicides was also relatively low; 72-h exposure to fosetyl-Al and mefenoxam resulted in 17.4 and 27.5% mortality, respectively. The IGR and fungicides increased the duration of the protonymphal stage by 1.2-1.8-fold, but they had no effect on the duration of subsequent life stages, nor on the duration of preoviposition, oviposition, and postoviposition periods of adult females. Total numbers and viability of eggs laid by mites exposed to the IGR and fungicides did not differ from the negative control, although the average rate of egg production during the oviposition of mites exposed to fosetyl-Al was increased. Pyriproxyfen, fosetyl-Al, and mefenoxam are likely to be compatible with S. scimitus under field conditions, because these pesticides caused little mortality of protonymphs, and they did not negatively affect the development and reproduction of S. scimitus under extreme laboratory conditions. In contrast, the use of chlorpyrifos in conjunction with S. scimitus is not recommended unless more comprehensive testing under semifield or field conditions demonstrates compatibility.

Effect of temperature on development and reproduction in Gastrophysa viridula (Coleoptera: Chrysomelidae)

The duration of development, reproduction and longevity of Gastrophysa viridula (DeGeer) was measured at constant temperatures and a long day photoperiod. At 18, 21.5, 25, and 28°C the average duration of development of the egg, larval and pupal stages and total development time (28.2, 21.6, 16.1, 15.0 days) decreased with temperature but the proportion of time spent in the egg, larval and pupal stages did not significantly change with temperature. Total development required 304.6 day degrees above the lower development threshold of 7.1°C. Pre-adult mortality and the rate of oviposition increased, and the duration of oviposition decreased with increasing temperature. Net reproduction rate Ro decreased (from 157 female eggs at 18°C to 75 female eggs at 28°C) and mean generation time T also decreased (from 45.5 days at 18°C to 24.1 days at 28°C) with increasing temperature. The intrinsic rate of population increase rm increased with temperature (from 0.111 at 18°C to 0.179 at 28°C). On a physiological time scale the average generation time T was 496 day degrees.