Proportion Of Female Offspring Research Articles

Relationship between parasitism and morphology of Trichogramma (Hymenoptera: Trichogrammatidae) on Spodoptera frugiperda (Lepidoptera: Noctuidae).

In this study, 5 species of Trichogramma Westwood were evaluated for the biological control of Spodoptera frugiperda (JE Smith), concerning the physical characteristics of female Trichogramma. The results showed that Trichogramma chilonis Ishii, Trichogramma dendrolimi Matsumura, and Trichogramma ostriniae Pang et Chen exhibited high parasitism rates, emergence rates, and offspring numbers, with the highest values observed for T. ostriniae. The ovipositor length of Trichogramma japonicum Ashmead and T. dendrolimi were longer than those of other species, and the hind tibia length was the shortest in Trichogramma cacoeciae Marchal. We further evaluated relationships between the parasitism ability of Trichogramma and various morphological indexes based on Spearman's rank correlation coefficients. A positive correlation was found between the parasitism rate and hind tibia length of T. cacoeciae. In T. dendrolimi, the parasitism rate was negatively correlated with ovipositor width and positively correlated with the length-width ratio of the ovipositor. A significant positive correlation was observed between the proportion of female offspring and the mother's ovipositor length in T. japonicum. However, there were no significant correlations between morphological indexes and indexes of parasitism in T. ostriniae. Overall, the parasitic abilities of T. chilonis on S. frugiperda eggs were significantly correlated with the morphology of the female ovipositors.

Diluent pH affects sperm motility via GSK3 α/β-hexokinase pathway for the efficient enrichment of X-sperm to increase the female kids rate of dairy goats

Dairy goats are the goats bred with the ability to produce large quantities of milk, and the increase of the female kid rate of breeding dairy goats is beneficial for milk production and economic benefits of dairy goat farms. Our previous study revealed that regulating the pH of dairy goat semen diluent to 6.2 or 7.4 respectively, the proportion of X chromosome bearing sperm (X-sperm) in the up and down layers of the tube after incubation was significantly higher than that of Y chromosome bearing sperm (Y-sperm) i.e. enriched X-sperm. In this study, fresh dairy goat semen collected in different seasons was diluted in different pH solutions to calculate the number and rate of X-sperm and to measure the functional parameters of enriched sperm. The artificial insemination experiments were performed with enriched X-sperm. The mechanisms of regulating the pH of diluent affecting sperm enrichment were further studied. The results showed that the proportion of enriched X-sperm in pH 6.2 and 7.4 diluents of sperm collected in different seasons showed no significantly different, but were significantly higher than that of the control group (pH 6.8). The in vitro functional parameters of X-sperm enriched in pH 6.2 and 7.4 diluent solution were not significantly different from those of the control group (P > 0.05). After artificial insemination with X-sperm enriched in pH7.4 diluent, the proportion of female offspring was significantly higher than that of the control group. It was found that the regulating pH of the diluent affected sperm mitochondrial activity and glucose uptake capacity via phosphorylating NF-κB and GSK3α/β proteins. The motility activity of X-sperm was enhanced under acidic conditions and weakened under alkaline conditions, which was conducive to the effective enrichment of X-sperm. This study demonstrated that the number and proportion of X-sperm enriched using pH 7.4 diluent were elevated, and the proportion of female kids was increased. This technology can be used for the reproduction and production of dairy goats in farms at large scales.

Impact of a nonnative parasitoid species on intraspecific interference and offspring sex ratio

In an assemblage of multiple predators sharing a single prey species, the combined effects of the component species may scale unpredictably because of emergent interspecific interactions. Prior studies suggest that chaotic but persistent community dynamics are induced by intra-/interspecific interactions between native and nonnative parasitoids competing over a shared host. Here, we test the impact of the nonnative parasitoid Heterospilus prosopidis (Hymenoptera: Braconidae) on the intraspecific interference and offspring sex ratio of the native parasitoid Anisopteromalus calandrae (Hymenoptera: Pteromalidae). We found that the nonnative parasitoid reduced intraspecific interference among native parasitoids and decreased the proportion of female offspring produced by the native parasitoid (predicted under conditions of reduced host availability). At higher host densities, the nonnative parasitoid contributed less to the total proportion of hosts parasitized, as its innate saturating Type II response changed to a dome-shaped Type IV response with increasing density of the native parasitoid, while the native parasitoid retained its increasing Type I response. This inverse host-density-dependent response between the two parasitoids and associated competitive superiority can explain the observed changes in parasitism; at high host densities, the searching efficiency of the native parasitoid increases via host feeding while the nonnative parasitoid experiences egg limitation. These results highlight the importance of the complementary top-down effects of multiple consumers on a single resource.

Fertilization potential test of sperm from nano monoclonal antibody injected goats

• Over 90 % of X bearing sperm could be available using NMA™ sex selection technique. • In vitro fertility potential of sperm sorted by NMA™ injection was comparable to that in the control group. • The percentage of female offspring was more than 90 %. Controlling the sex of an animal’s offspring has long been the dream of most livestock producers. To produce a very higher percentage of X chromosome bearing sperm, calcium phosphate nano monoclonal antibody (NMA™) against Guanzhong dairy goat sperm epitope was developed in advance, and the detailed development technique has been applied for patent protection. The present study focused on the fertilization potential detection of sperm which was treated by testis injection of NMA™ to implementing sex selection of Guanzhong dairy goat. Results showed that no significant differences in sperm viability, sperm velocities, acrosomal integrity and plasma membrane integrity, although the volume and density of a single ejaculate were slightly lower in goats from the NMA™ injection group than those of the control group. From the 6th to 30th week following NMA™ injection, the percentage of X chromosome bearing sperm was more than 90 %; at the week 40th, it dropped to 88 %. After the second NMA™ injection performed at the 40th week, over 90 % of sperm with X chromosome could be obtained again. Moreover, the in vitro fertilization capacity of sperm derived from NMA™ injection was the same as that of the control group. No significant difference in pregnancy rates and kidding rates was observed following artificial insemination using sorted sperm versus unsorted sperm, but the proportion of female offspring was more than 90 %, which was significantly higher in the sex sorted group than that of the control group. The sex determination technique presented here can be mainly applied to facilitate the mass production of female Guanzhong dairy goats.

Effects of male and female age on mating success in Tetranychus urticae Koch (Acari: Tetranychidae)

Females of most arthropods undergo multiple matings, most often with different males (polyandry) but sometimes with the same male (repeated matings). Arthropod seminal fluid contains components that are known to stimulate their fecundity and fertility. In spider mites, much is known about the paternal effects on offspring phenotypes, but nothing is known about how the age of males affects their fertility. In Tetranychus urticae Koch (Acari: Tetranychidae), the female offspring ratio is known to decrease with time. Here, we attempted to clarify whether the decrease is due to sperm deletion or a decrease in male fertility ability with age. Female age had significantly increase the fecundity. Older virgin females that mated with virgin males produced fewer female offspring. Female age at mating was negatively related to the mating time (= copulation time, sec) but not to the premating time (sec) after introduction of a virgin male. The mating time tended to decrease with increasing age at mating. Male fertility defined as the proportion of female offspring produced, and male fertility declines with male age and number of matings, even no female offspring produced in some cases. These results suggest that increased male age at mating is associated with sperm depletion, which in turn affects the number of progeny as well as the phenotype of the progeny in the subsequent generation.

Maternal metabolic syndrome induces liver injury and promotes tumor growth in the offspring

Abstract Objective Obesity is a growing disease entity affecting a third of women of reproductive age. Epidemiological studies show that children of obese mothers suffer from obesity, long-term morbidity and an increased rate of childhood cancers. However, the mechanisms of disease transmission remain unknown. The aim of this study is to test this hypothesis in a mouse model and shed light on the involved mechanisms of vertical transmission. Methods Female mice were fed a high fat or standard diet (HFD/SD) for 16 weeks before being mated with mice fed a normal diet. Corresponding diet was continued until weaning, all offspring were thereafter fed a SD. Metabolic profile, weight gain, liver enzymes and the gut microbiota profile were assessed in the offspring (n = 24). Additional groups of offspring (n = 48) were injected with a carcinogen (diethylnitrosamine) at week two, tumor characteristics were assessed by computed tomography scan at week 36. Results Mothers fed HFD developed obesity and non-alcoholic fatty liver disease (NAFLD). Female offspring of mothers fed HFD gained significantly more weight (+33.7%, p = 0.001), had increased alanine transaminase levels (62 vs 18 IU/L, p = 0.003) and a significantly altered liver histology exemplified by an increased NAFLD activity score (3.8 vs 0.6, p = 0.016). Expression levels of several candidate genes were studied of which FGF21 showed the largest differential expression between HFD and SD offspring (9 vs 1 2^ΔΔCT, p = <0.001). However, epigenetic analysis of FGF21 in the liver revealed no changes in methylation level between HFD and SD offspring. Furthermore, offspring of HFD mothers had a distinctly altered gut microbiome with lower proportions of Bacteroides caccae, Bacteroidales and Parasutterella excrementihominis. Interestingly, the proportion of female offspring developing tumors was significantly higher in offspring of HFD mothers (83 vs 44%, p = 0.011), the average total tumor volume was larger (234 vs 3.5mm3, p = 0.022) and the offspring developed more tumors (3.5 vs 0.6, p = 0.010). Conclusion Maternal obesity promotes liver tumor growth in the offspring, alters metabolic patterns and induces liver suffering in the progeny in a sex-dependent manner. The gut microbiome seems to play a role in this transmission of disease. Yet further research is needed to determine the vectors of transmission and evaluate preventive interventions in obese mothers.

Infection effects of the new microsporidian species Tubulinosema suzukii on its host Drosophila suzukii

Microsporidian infections of insects are important natural constraints of population growth, often reducing lifespan, fecundity and fertility of the infected host. The recently discovered Tubulinosema suzukii infects Drosophila suzukii (spotted wing drosophila, SWD), an invasive pest of many fruit crops in North America and Europe. In laboratory tests, fitness effects on larval and adult stages were explored. High level infection after larval treatment caused up to 70% pupal mortality, a decreased lifespan and a 70% reduced oviposition of emerging adults in biparental infection clusters. A shift to higher proportion of female offspring compared to controls suggested a potential parthenogenetic effect after microsporidian infection. A clear sex-linkage of effects was noted; females were specifically impaired, as concluded from fecundity tests with only infected female parents. Additive effects were noted when both parental sexes were infected, whereas least effects were found with only infected male parents, though survival of males was most negatively affected if they were fed with T. suzukii spores in the adult stage. Although most negative effects on fitness parameters were revealed after larval treatment, infection of offspring was never higher than 4%, suggesting limited vertical transmission. For that reason, a self-reliant spread in natural SWD populations would probably only occur by spore release from cadavers or frass.

Biological attributes of diapausing and non-diapausing Doryctobracon areolatus (Hymenoptera, Braconidae), a parasitoid of Anastrepha spp. (Diptera, Tephritidae) fruit flies

Doryctobracon areolatus(Szépligeti), a solitary endoparasitoid native to the Neotropics, attacks eggs and early instar larvae ofAnastrephafruit flies, and can enter diapause under tropical and subtropical conditions. We aimed to test if biological attributes, such as size, flight ability, starvation resistance, longevity and fecundity of diapausing individuals differ from those of non-diapausing ones. Parasitoids were obtained from a laboratory colony reared onAnastrepha ludens(Loew) larvae. Parasitized host puparia were sorted in two cohorts according to their diapause condition. Developmental time from egg to adult ranged from 18 to 31 days in non-diapausing parasitoids, and 70 to 278 days for diapausing individuals. Pupal weight and adult measurements were higher in non-diapausing than in diapausing parasitoids. There were no differences in adult longevity, starvation resistance, and emergence between diapausing and non-diapausing wasps. Flight ability and fecundity rates were greater in the non-diapausing than in the diapause cohort. The proportion of female offspring was greater in the non-diapausing cohort (42.5%), whereas in the diapausing cohort the male offspring proportion was greater (62.4%). Both cohorts produced diapause offspring, but the non-diapausing cohort produced more (26.6%) than the diapausing one (9.1%). Maternal age had a significant effect on the proportion of diapause offspring: in 26 to 34 days old non-diapausing females, 78.9% of their offspring entered into diapause. These results confirmed that diapause affects the biological attributes ofD. areolatus. The observed differences contribute to better understand the diapause influence on the colonization and rearing process of this species and its use as biocontrol agent.

Relative polyphagy of \u201cMediterranean\u201d cryptic Bemisia tabaci whitefly species and global pest status implications

The Bemisia tabaci whitefly was previously considered a single, highly polyphagous species, but is now accepted as a group of cryptic biological species. We investigated the host plant relations of two sister species, the “Mediterranean” (MED) composed of the Q1 and Q2 mitochondrial groups and the “ASL” species (formerly considered a MED group), to discover whether polyphagy was related to the global pest status. We compared their performance by measuring the oviposition rate, survival, fecundity and proportion of female offspring on 13 host plants from nine families. In addition, oviposition preference was compared among leaves of different ages. Significant (P < 0.05) differences were found between populations in all parameters, particularly in adult survival and fecundity. Females preferred strongly to oviposit on the oldest true leaf on tobacco and tomato and on young leaves of sweet potato and pepper. The greatest differences in fecundity occurred on bean, okra, squash, pepper and tobacco. Hosts favourable for all four populations were cotton and sweet potato; no offspring were produced on cassava, chard or tomato. Host ranges of Q1 populations from Europe and sub-Saharan Africa differed despite their close genetic relatedness at the mitogenome level. Discrepancies between the parental and offspring fitness were observed. Our findings show that (1) the species have differing but overlapping host plant ranges and (2) the Q1 is the most polyphagous and can utilise tobacco, which predisposes it to evolving resistance to neonicotinoids. Our findings contribute to the understanding of ecology of this pest species complex and aid the development of efficient pest control strategies.

Reproductive incompatibility between genetically differentiated populations of Tetranychus urticae from different host plants

The study of host plant adaptation in arthropods, and especially agricultural pests, presents great interest, as it relates to patterns of population isolation and differentiation, with effects ranging from gene flow restriction to speciation. Prompted by our earlier isoenzyme studies that revealed genetic differentiation of Tetranychus urticae (Koch) collected on citrus, compared to other host plants, we investigated crossing compatibility between T. urticae collected from citrus (lemon) trees (ELCI) and T. urticae collected from the weed Mercurialis annua (ELMA), in the same citrus grove. Crossing compatibility in haplodiploid species where unfertilised eggs develop into males, like T. urticae, is assessed based on both the number and the sex ratio of the offspring. When ELMA females were crossed with ELCI males, fecundity was not affected, however the sex ratio was significantly biased towards males (16.6 % females, compared to 66% in the control cross ELMAxELMA). In the reciprocal crosses (ELCIxELMA), fecundity was lower by 30% and the proportion of female offspring was reduced to 52% from 67 %, compared to the control. The fecundity of the F1 hybrid females was significantly reduced and the eggs they laid were less viable, compared to the non-hybrids, further reducing the reproductive potential of inter-strain crosses. Combined with previous data, these results suggest the existence of a citrus-associated T. urticae host race.

Parasitoid Diaeretiella rapae (Hymenoptera: Braconidae) Adjusts Reproductive Strategy When Competing for Hosts.

Parasitoid fitness depends on its ability to manipulate reproductive strategies when in competition. This study investigated the parasitism and sex allocation strategies of the parasitic wasp Diaeretiella rapae McIntosh at a range of host (Brevicoryne brassicae L.) and conspecific densities. The results suggest that D. rapae females adjust their progeny production and progeny sex ratio with changing competition. When foraging alone, female D. rapae parasitize larger number of B. brassicae nymphs when the number of available hosts is increased, but the overall proportion of parasitized hosts decreases with increase in host density. The proportion of female offspring also decreases with elevated host density. Increase in the number of female D. rapae foraging together increased total parasitism, but reduced relative contribution of each individual female. The number of female progeny decreased when multiple females competed for the same host. However, foraging experience in the presence of one or more conspecifics increased the parasitism rate and proportion of female progeny. Competing females were more active during oviposition and had shorter lives. The study suggests that both host and foundress (female parasitoid) densities have significant effect on progeny production, sex allocation, and longevity of foraging females.

Comparison of biological development of Blattisocius dentriticus (Blattisocidae) fed on Tyrophagus putrescentiae (Acaridae) and Megninia ginglymura (Analgidae)

ABSTRACTThis study evaluated Blattisocius dentriticus (Berlese) as a candidate predator of two mite species of public-health importance for humans and animals. We observed the development time, reproduction, survival and sex ratio of this predatory mite when fed on one of two pest mites, Tyrophagus putrescentiae (Schrank) and Megninia ginglymura (Mégnin), under laboratory conditions, at a temperature of 25 ± 1°C and 80 ± 5% relative humidity, in the dark. The study started with 30 experimental units containing M. ginglymura as a food source and 30 containing T. putrescentiae, each with an egg of B. dentriticus obtained from fertilized females. The length of the pre-oviposition period was significantly longer when M. ginglymura was used as food, compared to T. putrescentiae. The life-table parameters for B. dentriticus differed on the two diets. These parameters indicated that the population of B. dentriticus fed on T. putrescentiae increased about 7.53 times (Ro = 7.53) every 14.3 days (T = 14.3), corresponding to a daily population growth of about 15% (λ = 1.15), i.e. a production of 0.14 female per female per day (rm = 0.14). B. dentriticus fed on M. ginglymura showed lower values (Ro = 2.79; T = 23.76; λ = 1.04; rm = 0.04). The gross reproductive rate (GRR) and the proportion of female offspring were higher on T. putrescentiae (GRR = 10.73; ratio of females to males = 0.87). Our study demonstrated that B. dentriticus is a potential predator, developing and reproducing successfully on the two mites T. putrescentiae and M. ginglymura. Blattisocius dentriticus performed better against T. putrescentiae.

Laboratory Performance Predicts the Success of Field Releases in Inbred Lines of the Egg Parasitoid Trichogramma pretiosum (Hymenoptera: Trichogrammatidae).

In this study we assessed the relationship between the laboratory and field performance of different isofemale lines of Trichogramma pretiosum Riley. In comparative assays, we used three rare mitochondrial haplotypes as genetic markers of the isofemale lines, and by introgressing these mitochondrial haplotypes into each of 15 genetically different nuclear lines, also tested the assumption that mitochondria are neutral markers. In a laboratory trial, 45 isofemale lines (15 nuclear genotypes x three mitochondrial haplotypes) were ranked in three categories (best, intermediate and worst) according to the mean offspring production and the proportion of female offspring. Subsequently, lines from each of the three categories were selected for field releases to quantify field parasitism on Ephestia kuehniella. Temporally separate releases were done in a transgenic Bt cornfield, with four plots, each with 50 points of recapture. The points of recapture consisted of trap cards with eggs of E. kuehniella collected daily. The trap cards were maintained in the laboratory at 25°C until the adult wasps emerged, and the maternal identity of the wasps was determined using qPCR and high-resolution melt curve analysis to determine the mitochondrial haplotype. The results showed that these measures of laboratory performance (fecundity and offspring sex ratio) were good predictors of field success in T. pretiosum. We also report strong evidence discrediting the assumption that mitochondria are neutral, in view of the correlation between performance and mitochondrial haplotype.

Factors affecting the parasitism rate and the number and sex ratio of offspring of Asecodes hispinarum Bouček (Hymenoptera: Eulophidae), a biological control agent of Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae)

To optimise the production of Asecodes hispinarum Bouček (Hymenoptera: Eulophidae), a parasitoid of coconut leaf beetle, Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae), some of the factors affecting rates of parasitism, number of offspring produced per host and sex ratio of A. hispinarum were investigated. The numbers and sex ratio of A. hispinarum offspring per host reduced significantly at extreme low humidity (30% relative humidity [RH]), but there was no significant effect on parasitism. Photoperiod had no significant effects on any of the life traits tested. A. hispinarum was able to reproduce via arrhenotoky, and while increasing the proportion of female parents increased the number of parasitoids produced, the proportion of female offspring decreased. Older females showed a lower rate of parasitism than young females, however, maternal age did not affect the number or the sex ratio of offspring. Increasing the number of hosts offered to a pair of parasitoids significantly increased the number of parasitised hosts but decreased the parasitism rate while the sex ratio of progeny was not affected. Present work showed that to maximise the production of female parasitoids, a parasitoid/host ratio of 1:1, using one-day old A. hispinarum at a female/male ratio of 3:1 and RH of at least 55% is recommended.

Host Preference byDiachasmimorpha longicaudata(Hymneoptera: Braconidae) Reared on Larvae ofAnastrepha fraterculusandCeratitis capitata(Diptera: Tephritidae)

ABSTRACT The preferences of Diachasmimorpha longicaudata (Ashmead) for larvae of Anastrepha fraterculus (Wiedemann) and Ceratitis capitata (Wiedemann) were evaluated under laboratory conditions in no-choice and dual-choice tests, based on percent parasitism, proportion of emerged parasitoids, proportion of female offspring, and number of parasitoid female visits to and ovipositor probes on the artificial oviposition device as different measures of host preference. In no-choice tests D. longicaudata females did not demonstrate a significant preference between C. capitata and A. fraterculus larvae. Nevertheless, D. longicaudata females showed a strong preference for A. fraterculus larvae in dual-choice test. Although female biased parasitoid progeny resulted in all assays, significantly more D. longicaudata female offspring emerged from A. fraterculus pupae than from C. capitata pupae. Thus, this study confirmed that both C. capitata and A. fraterculus are appropriate host for rearing D. longicaudata, but a...

The parasitoid Praon volucre (Hymenoptera: Braconidae: Aphidiinae) as a potential biological control agent of the aphid Uroleucon ambrosiae (Hemiptera: Aphididae) on lettuce in Brazil

The aphid Uroleucon ambrosiae (Thomas) is one of the principal pests found on greenhouse lettuce crops, and there is no efficient biological control agent of this pest in Brazil. This work evaluates the aphid U. ambrosiae as a host for the parasitoid Praon volucre (Haliday), aimed at using P. volucre as a potential biological control agent of U. ambrosiae on lettuce. As Macrosiphum euphorbiae (Thomas) is a common host of P. volucre in the field, the development of the parasitoid was compared on these two aphid species. Twenty nymphs of the 2 nd instar were kept with P. volucre for one hour at 22 ± 1°C, 70 ± 10% RH and a 12 h photo- phase. The size of the aphid's tibiae at the moment of oviposition indicated that there was no significant size difference between U. ambrosiae (0.6 ± 0.02 mm) and M. euphorbiae (0.7 ± 0.03 mm). When mummies were formed, M. euphorbiae had significantly longer tibia (1.5 ± 0.03 mm) than U. ambrosiae (1.4 ± 0.02 mm). No significant differences were detected in the percentage emer- gence (74.9 ± 7.92 and 87.5% ± 3.31 for U. ambrosiae and M. euphorbiae, respectively), or proportion of female offspring (56.2 ± 7.62 and 44.2 ± 7.14%). The development time from oviposition to adult and longevity of females and males of P. volucre reared on the two host species were not different. High parasitism levels were recorded for both host aphid species, but the percentage para- sitism of M. euphorbiae (54.4 ± 4.40) was higher than of U. ambrosiae (35.6 ± 5.30). Female parasitoids reared on M. euphorbiae had longer tibiae (0.78 ± 0.01 mm) than those reared on U. ambrosiae (0.72 ± 0.01 mm). Our results demonstrate that the alternative host species U. ambrosiae, compared to the natural host species M. euphorbiae, affects the female's size, but did not affect parasitoid development time, longevity, emergence or sex ratio. The parasitoid P. volucre seems to be a good candidate for using as a bio- logical control agent of U. ambrosiae on lettuce in Brazil.

Host Size and Oviposition Site Effects on Sex Ratio of Pupal Parasitoid Muscidifurax zaraptor (Hymenoptera: Pteromalidae)

This study examined how the size of host pupae of Musca domestica L. and exposure of host spiracles affected parasitism and sex ratio of Muscidifurax zaraptor Kogan & Legner (Hymenoptera: Pteromalidae). Based on a model by Charnov et al. (Nature [Lond.] 289: 27-33, 1981), we predicted that a lower proportion of female offspring would be produced on large hosts when large hosts were presented alone than when both small and large hosts were presented simultaneously. This prediction was supported, suggesting that females used relative cues for determining host size. We also predicted a greater proportion of female eggs would be produced on small hosts when only small hosts were presented than when both small and large hosts were presented simultaneously. This prediction was not supported, suggesting that females also used absolute cues for assessing host size. Host size had no significant effect on the thorax widths of offspring. However, the head widths of offspring varied with pupal size, with wasps emerging from large pupae having larger thoraces. There was a difference in parasitism depending on pupal orientation; house fly pupae that had posterior spiracles exposed (i.e., anterior spiracles concealed) were less often parasitized than when the anterior spiracles were exposed. Pupal position and sex ratio were not related. Finally, females spent less time drilling through posterior spiracles than through anterior spiracles.

Release and establishment ofCotesia flavipes for biological control of maize stemborers in Zimbabwe

Five populations of the crambid stemborerChilo partellus (Swinhoe) and one of the noctuid borerBusseola fusca (Fuller) from Zimbabwe were evaluated for their suitability for immature development of the exotic braconid larval parasitoidCotesia flavipes Cameron. Successful parasitoid development occurred only onC. partellus but parasitism as well as egg-to-adult development time did not vary among the five populations. Smallest parasitoid broods, and sex ratios as the proportion of female offspring, however, were produced withC. partellus from the Muzarabani area of Zimbabwe.Co. flavipes became successfully established in five out of eight locations, where it had been released in July 1999 and the 2004/05 summer season. Its spread and impact, however, still need to be assessed.

Ratio of male to female births in the offspring of BRCA1 and BRCA2 carriers

A recent report based on 68 families, including 17 with mutations in BRCA1, suggested that there was an excess of female offspring born to BRCA1 mutation carriers. We have examined the gender ratio among offspring of 511 mutation carriers from 116 BRCA1 families, 77 and 39 from Australia and the United States, respectively. We found no evidence for a significant deviation from the expected proportion of female offspring in the Australian pedigrees, but there was an excess of female offspring in pedigrees from the USA. Ascertainment bias probably explains this bias, rather than a link with X-chromosome inactivation as previously suggested, because the families from the USA were ascertained for the purposes of linkage studies whereas those from Australia were ascertained through Familial Cancer Clinics to which they had been referred for clinical genetic counseling and mutation testing.

Effects of Neonicotinoid Insecticides on the Bionomics of Twospotted Spider Mite (Acari: Tetranychidae)

Previous reports indicate that applications of imidacloprid, a neonicotinoid insecticide, can lead to population buildups of twospotted spider mite, Tetranychus urticae Koch, in the field. Moreover, laboratory studies showed enhanced fecundity of T. urticae after an imidacloprid treatment. In this study, experiments were conducted in the greenhouse to investigate the potential effects of imidacloprid and several other neonicotinoid insecticides on fecundity, egg viability, preimaginal survivorship, and sex ratio of T. urticae (German strain WI) on French beans, Phaseolus vulgaris L. Four insecticides, i.e., imidacloprid (Confidor 200SL), thiacloprid (Calypso 480 SC), acetamiprid (Mospilan 70 WP), and thiamethoxam (Actara 25 WG), were tested at field-relevant (100, 120, 125, and 95 ppm) and sublethal doses (10, 12, 12.5, and 9.5 ppm), respectively. Both spray and drench applications were tested. At field-relevant doses, fecundity of T. urticae decreased and was lower in the treatments compared with the untreated control, whereas preimaginal survivorship and proportion of female offspring (i.e., sex ratio) were lower compared with the control. At sublethal doses, no significant differences were found among the treatments. Data on egg viability, preimaginal survivorship, and sex ratio at sublethal doses followed the same trends as at field-relevant doses. In an additional experiment, the metabolism of imidacloprid into monohydroxy-imidacloprid, olefine, guanidine, and 6-chloronicotinic acid was compared with the oviposition pattern of T. urticae. These findings are discussed with regard to previous laboratory and field observations of imidacloprid-induced fertility increases in T. urticae.