Adult Emergence Rate Research Articles

Life cycle and morphometrics of fall armyworm (Spodoptera frugiperda) (Lepidoptera: noctuidae) on maize crop

Fall armyworm (FAW) (Spodoptera frugiperda J.E. Smith) is a polyphagous pest, native to North and South America and is invasive in Eurasia and Africa. Life cycle and morphometric studies with the invasive population of FAW in Nepal were conducted under laboratory conditions in Chitwan, Nepal. Gravid females laid an average of 156.25 eggs per egg batch, with an average of 979.43 eggs during their whole lifetime. The average pre-oviposition period was 3.75 days, oviposition period was 3 days, the larval developmental period was 16.31 days, the pupal period was 9.69 days, and the whole life cycle (egg to egg) averaged 33 days. The average length of each instar larva from I to VI instars was 1.5, 3.6, 7.1, 11.6, 18.5, and 34.4 mm, respectively. Head capsule widths for each instar were 0.35, 0.47, 0.8, 1.37, 2.11, and 2.7 mm, respectively for instars first through sixth. Pupal and adult emergence rates were 98.9 and 97.2%, respectively, with a male to female ratio of 1:1.3. Larval mortalities of the I, II, and III instars were 70, 66, and 12%, with no mortality in the IV, V and VI instars. Adult longevity was 20.73 days for males and 22.78 days for females. These findings are useful to design an integrated management protocol of the fall armyworm. SAARC J. Agric., 20(1): 77-86 (2022)

Host Size Preference of the Leafcutter Ant Parasitoid Eibesfeldtphora tonhascai(Diptera: Phoridae).

Eibesfeldtphora tonhascai Brown(Diptera: Phoridae) is a natural enemy of Atta sexdensLinnaeusand Atta laevigata Smithand is considered a promising candidate for the biological control of these ants. The aim of this study was to verify if E. tonhascai has a preference for specific sizes of A. sexdens foragers and whether this parasitoid demonstrated host species preference when comparing parasitism of A. sexdens and A. laevigata. Worker ants were classified into four different size groups and introduced into an attack arena with one E. tonhascai female. To verify host species preference, both A. sexdens and A. laevigata workers were placed in the attack arena together with one E. tonhascai female. A no-choice test was also performed, when each ant species was offered to a phorid female at different times. Eibesfeldtphora tonhascai performed the highest number of inspection flights, attempted attacks, and actual attacks against A. sexdens workers with a cephalic capsule size of 3-5mm. When comparing attacks on A. sexdens and A. laevigata workers, they were equally inspected, attacked, and the total parasitism rates were similar. However, the phorid adult emergence rate was significantly higher in the A. sexdensparasitized workers. We conclude that E. tonhascai females express preference for parasitizing larger hosts (cephalic capsule width of 3-5mm), but do not display a preference for host species when comparing A. sexdens versus A. laevigata, and thus can similarly contribute to both leafcutter ants' natural biological control.

Toxicity and Sublethal Effects of Fluxametamide on the Key Biological Parameters and Life History Traits of Diamondback Moth Plutella xylostella (L.)

Fluxametamide, a novel isoxazoline insecticide, is newly registered for the control of various lepidopteran, coleopteran and thysanopteran insect pests on lethal and sublethal levels. In the present study, the toxicity and sublethal effects of fluxametamide on diamondback moth Plutella xylostella (L.), an invasive lepidopteran foliage feeder of cruciferous vegetables, were assessed to explore its bio-ecological impact on pest populations. The toxicity of fluxametamide to the third instar larvae of P. xylostella was 0.18 mg L−1 (LC50) at 72 h bioassay. After treatment with LC10 and LC30 concentrations of fluxametamide, the fourth instar larval duration, the rate of deformed pupa and adults, and the adult pre-oviposition period were significantly increased, whereas the pupation rate and pupal weight were significantly decreased in the F0 generation. In the F1 generation, sublethal effects of fluxametamide were indicated by a reduced fecundity, rate of pupation and adult emergence, pupal weight, and adult longevity, however a significant increase in eggs and total larval duration, deformed adults rate, and total longevity and pre-oviposition period was observed in the offspring. The intrinsic rate of increase (r), finite rate of increase (λ) and net reproductive rate (R0) of sublethal treatments were significantly lower than the control. The relative fitness of F1 was 0.68 and 0.64 in LC10 and LC30 treatments, respectively. The LC30 fluxametamide treatment exhibited increased glutathione S-transferase activities (elevated 1.433-fold) in P. xylostella. Our results suggest that in addition to its high lethal toxicity, the sublethal concentrations of fluxametamide might suppress the reproduction, development and survival of the P. xylostella population and its progeny, which can help to optimize integrated pest management program.

Influence of different hosts on biological parameters of the fruit fly Ceratitis capitata (Diptera: Tephritidae) in Tunisia

The Mediterranean fruit fly, Medfly, Ceratitis capitata (Wied.), is one of major and destructive insect pests of fruit crops worldwide. The influence of seven species of fruit on the biological parameters of C. capitata was examined. The fruits tested were: Citrus sinensis (Thomson navel L.), Clementine (Citrus clementica L.), Mandarin (Citrus deliciosa or reticulate L.), Lemon (Citrus limon L.), Maltese (Oranger de Malte), bitter orange (Citrus aurantium L.), and Peach (Prunus persica L.). The highest number of eggs laid by the females was observed in Citrus aurantium (13.62±0.69) and the lowest in Citrus deliciosa (10.05±0.20). The longest egg incubation time was observed in Citrus limon (2.66±0.51) and the shortest was observed in Prunus persica (2±0.00). The shortest pupal development time (8.83 days) was observed in Prunus persica, whereas the longest (11.66days) was in Citrus limon. Adult emergence rates were generally high (>60%), except for Citrus sinensis. The highest sex ratio was observed in Citrus aurantium (0.579±0) and the lowest was observed in Citrus limon (0.271±0.01). Life expectancy at pupal eclosion was recorded at adult C. capitata. The lives of adult flies were shorter or longer according to the species. Males lived longer than female on all host plants. Results showed the most suitable host-fruit for C. capitata was peach; although Citrus aurantium were shown to be the preferred host for oviposition and seem to have an important role as alternative host between Mars and Mai, allowing the continuous development of C. capitata throughout the year. The importance of these results could be used to determine perfect times for management treatments.

Effect of pyriproxyfen on development and survival of Anopheles gambiae sensu stricto under forested and deforested areas

BackgroundThe land cover changes in the form of deforestation are known for their impact on enhancing Anopheline life-history traits. In most cases, these traits depend on environmental parameters such as temperature and light. Pyriproxyfen is an insect growth regulator juvenile hormone (JH) designed to inhibit adult mosquito emergence. It is an effective biolarvicide in controlling immature stages of malaria vectors and many other insects. Despite the known efficiency of pyriproxyfen in malaria vector control, but the understanding of its performance under deforested or afforested areas is not clear. The present study aimed at evaluating the impact of pyriproxyfen on development and survivorship of Anopheles gambiae s.s. in forested and deforested areas. Tests of two dosages (0.03 ppm.ai. and 0.3 ppm.ai.) of pyriproxyfen were done in standardized semi-field conditions under ambient temperature and light in netting screened environment. The plastic artificial microcosms containing 1 kg of soil and 2000 mL of dechlorinated water were used. First instars larvae were distributed in densities of 20, 40, and 60 in six replicates each, to form a total of 18 microcosms per each land cover type. Larvae mortality, development, and survival time were monitored and recorded after every 24 h until pupation. Emerging adults from pupa were recorded, and their sexes were identified.ResultsPyriproxyfen increased Anopheles gambiae larvae mortality rates and larvae developmental time of first instar larvae to pupal at densities of 20, 40 and 60 larvae in forested area (p < 0.05). Also, the larvae survival time was found to be longer in forested area compared to deforested area (p < 0.05) except at the density of 20 larvae. Pyriproxyfen reduced larvae pupation rates by 88% in forested area and it had 100% adult emergence inhibition regardless of land cover type and pyriproxyfen concentration, except at the density of 60 larvae exposed to 0.03 ppm, where adult emergence rate of 6.7% was detected.ConclusionThese findings suggest that, the efficacy of pyriproxyfen against Anopheles gambiae s.s. larvae and pupae is dependent on land cover types and its larvicidal effect can be increased by presence of trees canopy covers. Therefore, reviving forestry schemes and community afforestation programmes could have a positive impact on mosquito larval control by using larvicides. Also, increasing land canopy cover can be opted as a way to discourage the development and survival of potential malaria vectors.

Involvement of Laccase2 in Cuticle Sclerotization of the Whitefly, Bemisia tabaci Middle East-Asia Minor 1.

Simple SummaryBemisia tabaci Middle East–Asia Minor I (MEAM1) is a widely distributed invasive agricultural pest that causes extensive damage to agricultural, horticultural, and ornamental crops. Laccase2 (Lac2), a phenol oxidase, plays an important role in cuticle tanning of some insects. However, the function of Lac2 in whitefly remains unclear. In this study, we identified a BtLac2 gene in MEAM1 that is expressed in all developmental stages, and its expression in the cuticle is especially high. Knockdown of BtLac2 in nymphs produced thinner and fragile cuticles, which significantly increased the mortality rate and extended the development duration of nymphs, as well as further decreasing the emergence rate of adults. Overall, BtLac2 plays an important role in cuticle hardening of whitefly, suggesting a potential management strategy using RNAi to knock down BtLac2 expression.Cuticle sclerotization is critical for insect survival. Laccase2 (Lac2) is a phenol oxidase that plays a key role in cuticle formation and pigmentation in a variety of insects. However, the function of Lac2 in whitefly, Bemisia tabaci, remains unclear. In this study, we identified a BtLac2 gene in B. tabaci MEAM1 and found that BtLac2 was expressed in all stages. It was highly expressed in the egg stage, followed by nymph and adult. Moreover, the expression of BtLac2 was higher in the cuticle than in other tissues. Knockdown of BtLac2 in nymphs produced thinner and fragile cuticles, which significantly increased the mortality rate, extended the development duration of nymphs, and decreased the emergence rate of adults. This result demonstrates that BtLac2 plays an important role in the cuticle hardening of B. tabaci and suggests a potential management strategy using RNAi to knock down BtLac2 expression.

Modifications of Traditional Formulas to Estimate and Project Dependency Ratios and Their Implications in a Developing Country, Bangladesh.

Traditional dependency ratios based on the United Nations’ old age definition (≥ 65 years) appear to be an inappropriate indicator for many developing countries, including Bangladesh. Bangladesh, with a retirement age of 59 in many sectors, defines old age as ≥ 60 years, whereas the United Nations documents 60–64 years as working age. This study offers two modifications to the traditional formulas of dependency ratios and compares the modified measures against the traditional measures from 1975 to 2100. Using data from the United Nations and the World Bank, (i) we moved the cut-off for ‘old age’ to 60 instead of 65 years, considering 15–59 years as ‘potentially working’, and (ii) we used the economically active population instead of the entire working-age population. Using our modified calculations, the growth rate of older adults (≥ 60 years) will be at its peak (4.6%) between 2020 and 2030 and continue to increase until 2085, though we will observe a negative population growth after 2055, and 2020–2040 appears to be the best time for reaping the highest demographic dividend. Compared to our modification, the traditional formula undercounted the older adults substantially, predicting a much lower demographic and financial burden. The modifications and associated estimates are important in advancing our understanding of dependency ratios in Bangladesh and have policy and practical implications in preventing the inaccurate representation of demographic and financial issues, and they are useful for planning for geriatric care, social safety nets, and healthy aging. The modified formulas may also be applicable in other countries which adopt ≥ 60 years as an old-age threshold.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11113-022-09720-8.

Responses of Fungi Maggot (Bradysia impatiens Johannsen) to Allyl Isothiocyanate and High CO2.

Botanical pesticide is highly recommended for integrated pest management (IPM), due to its merits such as environmental friendliness, safe to non-target organisms, operators, animals, and food consumers. The experiment was conducted to determine the lethal and sub-lethal effects of allyl isothiocyanate (AITC) on eggs, third instar larvae, pupae, and females and males of Bradysia impatiens Johannsen (B. impatiens). Different concentrations of AITC under ambient CO2 by the conical flask sealed fumigation method were used for the experiment. The results showed that there was a significant linear relationship between different concentrations of AITC and the toxicity regression equation of B. impatiens. The sub-lethal concentrations of AITC had significant effects on the larval stage, pupal stage, pupation rate, pupal weight, adult emergence rate, and oviposition. The pupation rate, pupal weight, and adult emergency rate were significantly (p < 0.05) affected by AITC fumigation. The pupation rate was the lowest after fumigation treatment of AITC at LC50 (36.67%), followed by LC25 (41.94%), compared with the CK (81.39%). Female longevity was significantly (p < 0.05) shortened by fumigation at LC25 (1.75 d) and LC50 (1.64 d), compared with that of CK (2.94 d). Male longevity was shorter at LC25 (1.56 d) than at LC50 (1.25 d) and had no significant difference between these two treatments. The fumigation efficiency of AITC was significantly increased under high CO2 condition. Furthermore, detoxification enzyme activities and antioxidant enzyme activities were accumulated under high CO2 condition. The fumigation method in the application of AITC can be useful in areas where B. impatiens is a major concern.

Identification of a Cordyceps fumosorosea Fungus Isolate and Its Pathogenicity against Asian Citrus Psyllid, Diaphorina citri (Hemiptera: Liviidae).

Simple SummarySome entomopathogenic fungi are highly pathogenic to Diaphorina citri, which is the mainly transmitting vector of CLas. In our study, we isolated an entomopathogenic fungus strain from an adult cadaver of D. citri. The isolate was identified as Cordyceps fumosorosea, based on morphology and ITS sequence analysis, and named C. fumosorosea SCAU-CFDC01. We further evaluated its pathogenicity against D. citri nymphs and adults under laboratory and greenhouse conditions. The laboratory results showed that C. fumosorosea SCAU-CFDC01 was most pathogenic to young nymphs, followed by old nymphs and adults. Furthermore, the results on greenhouse experiments revealed that C. fumosorosea SCAU-CFDC01 not only had high pathogenicity against nymphs, but also had serious negative effects on adults from nymphs treated, including emergence rate of adults and female longevity. Our results showed C. fumosorosea SCAU-CFDC01 was highly pathogenic to D. citri, and these findings will facilitate mycoparasite development for biological control of D. citri.Diaphorina citri is the mainly transmitting vector of the citrus huanglongbing pathogen, which causes severe losses in in the citrus industry. In this study, we isolated a new entomopathogenic fungus, identified as member of Cordyceps fumosorosea based on morphology and ITS sequence analysis. We named C. fumosorosea SCAU-CFDC01 and evaluated its pathogenicity against D. citri nymphs and adults by immersion under laboratory and greenhouse conditions. Results showed that SCAU-CFDC01 was most pathogenic to young nymphs, followed by old nymphs and adults. The LC50 values of the fungus on nymphs and adults showed a declining trend over a 2–7-day period after inoculation. The LT50 (lethal time for a certain concentration to cause 50% mortality) values also presented a decreasing trend along with increasing conidia concentrations. For the results on greenhouse experiments, when 3rd and 5th instar nymphs were inoculated with 1 × 105 conidia mL−1, the survival rate of nymphs were lower, and the emergence rate of adults and female longevity was significantly reduced compared with the control. However, there were no significant effects on sex ratio of adults and male longevity. Our results showed SCAU-CFDC01 was highly pathogenic to D. citri, and may promote mycoparasite development for biological control of D. citri.

Effect of Different Types of Iraqi Soils and Burial Depths of the Larvae and Pupae on the Adult Emergence Rate of the Mediterranean Fruit fly, Ceratitis capitata (Wiedemann), Under Laboratory Conditions.

This experiment was conducted to study the effect of soil type (structure) and different dumping depths of larvae and pupae within the soil on the emergence rate of adults of the Mediterranean fruit fly, Ceratitis capitata, which is considered a major pest affecting citrus and stone fruits orchards. Three soil types were selected: sandy clay, clay loam and loam and for each type six dumping depths were tested (3, 5, 7, 10, 15 and 20 cm).The results showed that the soil type had a significant effect on the adults emergence rate, and the highest rate was recorded for the sandy clay soil, when using the last larval instars (pre-pupae) and pupal stages, and reached 55.28 and 51.66%, respectively. The results also showed that the soil type and dumping depth together have a significant effect on the adults' emergence rate of the Mediterranean fruit fly. The sandy clay soil and the two depths, 5 and 7 cm, gave the highest emergence rate which was 73.3 and 71.67%, respectively, when using the last larval instar. Whereas, the clay loam soil gave at 3 and 5 cm soil depths a 70% emergence rate for both dumping levels. The results also showed that the two soil types sandy clay and loam showed that the emergence of adults continued even at 20 cm depth. The results obtained in this research can be incorporated to the practices used for the integrated management of the Mediterranean fruit fly C. capitata. Keywords: Mediterranean fruit fly, soil type, soil depth, adults' emergence rate.

Age and growth rates of a translocated chub Squalius cephalus chalk-stream population with comparison to indigenous riverine populations in England

Introduced fishes into lowland rivers can result in invasive populations establishing and then dispersing, where knowledge of their life history traits contributes to understandings of their invasion ecology. Here, the age and growth rates of a translocated chub Squalius cephalus population were assessed in the River Frome, a lowland chalk-stream in Southern England, where chub was introduced approximately 15 years ago. The results were assessed in relation to 35 riverine indigenous chub populations in England. Across these populations, individual chub were present to lengths over 550 mm and aged to at least 19 years old. In samples collected from the River Frome, however, no fish were present over 300 mm and age 4+years. Growth rate analyses of both the annual length increment produced between age 1 and 2 years (juvenile growth rate) and length at the last annulus (adult growth rate) revealed that both of these were relatively high in the River Frome population, being among the fastest of all sampled populations. It is suggested these fast growth rates were the response of the fish to their new environment, facilitating their establishment and colonisation through, for example, enabling reproduction at relatively young ages.

Effect of body size on the long-term reproductive output of eastern Atlantic loggerhead turtles Caretta caretta

We assessed the relationship between body size and several important life history parameters to understand the demographic significance of interpopulation variability in the body size of loggerhead turtlesCaretta carettanesting on Boa Vista Island (Cabo Verde). The adult growth rate (0.34 ± 0.60 cm yr-1), annual mortality rate (0.13, 95% CI: 0.12-0.15) and remigration interval (3.1 ± 1.2 yr) were independent of curved carapace length (minimum curved carapace length [CCLmin]). Conversely, the body condition index decreased significantly with female CCLmin. The clutch size, mean egg mass, mean hatchling straight carapace length and mean hatchling mass increased significantly with female CCLmin. However, there was no relationship between female size and hatching success. Randomization and bootstrapping were used to incorporate variability when calculating the average individual fecundity over 20 yr, a period that accumulated, on average, 94% of the adult mortality. The overall fecundity during this period increased with carapace length at first maturity (71 cm CCLmin: 815 eggs, 95% CI: 653-863; 80 cm CCLmin: 906 eggs, 95% CI: 822-959; 90 cm CCLmin: 1089 eggs, 95% CI: 926-1415). However, only 8% of the adult females nesting on Boa Vista Island are larger than 90 cm CCLmin, and they produce less than 12% of the total annual egg production. The scarcity of large females might result from a shortage of high-quality foraging grounds where females may reach first sexual maturity at a large carapace length and from the combined effect of a small carapace length at first sexual maturity, low adult somatic growth and high adult mortality.

Effects of Microalgal Food Quantity on Several Productivity-Related Parameters of the Calanoid Copepod Bestiolina similis (Calanoida: Paracalanidae)

The optimization of copepod feeding protocol is paramount to improve culture productivity and to maintain favorable water quality parameters overtime, as well as saving operational costs by preventing the production of unnecessary quantities of microalgae. The influence of microalgal feeding concentration on major parameters related to culture productivity of the calanoid copepod Bestiolina similis (Paracalanidae) was investigated in a series of laboratory experiments. B. similis was fed eight different concentrations (0, 150, 300, 600, 900, 1,200, 1,500 and 1,800 μgC l–1) of a mixed microalgal diet consisting of Tahitian strain of Isochrysis species, Pavalova 50 and Tetraselmis chuii at 1:1:1 carbon ratio. The results indicate that female daily and cumulative egg production over lifespan, egg hatching rate, naupliar and copepodite survival and development, adult female life expectancy, population growth and fecal pellet production rate (FPPR) were all significantly affected by microalgae feeding ration. Conversely, no significant influence could be established between microalgae food concentration and egg diameter or adult sex ratio. Feeding rations as low as 150 μgC l–1 led to lower egg hatching rates, survival and development, adult female life expectancy and population growth compared with the higher microalgae rations tested. Feeding concentration ≤ 900 μgC l–1 significantly limited female daily egg and fecal pellet production rate, as well as their cumulative egg production over lifespan, when compared to a level of 900 μgC l–1. Bestiolina similis fed with 1,200 μgC l–1 significantly improved female egg and fecal pellet production when compared to the lower treatments and was responsible for the highest female lifespan egg production and population growth observed among all treatments. Feeding rations as high as 1,500 μgC l–1 and 1,800 μgC l–1 did not lead to significant improvement in any of the parameters measured. This is likely due to a saturation effect at high food concentration which is known to decrease calanoid copepods feeding efficiency. Finally, B. similis FPPR, used as a proxy for ingestion, was found to saturate at a microalgae concentration of 783.4 μgC l–1 using a non-linear Michael-Menton (2 parameters), indicating that CVI female ingestion did not increase significantly above this concentration. Based on the above results it is recommended that B. similis cultures should be fed at a concentration of 1,200 μgC l–1, and not above, as rations &amp;gt; 1,200 μgC l–1 will not significantly improve any of the productivity-related parameters observed in this study. Feeding rations should never be below 783.40 μgC l–1 as this is the threshold level below which adult female ingestion rates become limiting.

Evaluating the effects of Bt protein Vip3Aa on immature Propylea japonica (Thunberg) (Coleoptera: Coccinellidae)

BackgroundGenetically modified (GM) crops have become a common tool for managing insect pests of economic importance. However, before their commercialization, bio-safety evaluation on non-target arthropods such as pollinators and biological control agents is a pre-requisite to save services rendered by them in agro-ecosystem.ResultsIn the present experiment, the potential adverse effects of Bt protein (Vip3Aa) were studied on the life table parameters (pupation and emergence rates, 7-day larval weights, larval development time, and adult weight) of a predatory beetle, Propylea japonica (Thunberg) (Coleoptera: Coccinellidae) in the laboratory. P. japonica was exposed to Bt protein incorporated in synthetic diet at the rate of 200 µg/g of fresh weight of diet. Temporal stability, bioactivity and the uptake of insecticidal protein were confirmed by enzyme-linked immunosorbent assay and a sensitive insect bioassay. The results indicated that pupation and adult emergence rates did not differ significantly from that of negative control (pure synthetic diet). Similarly, the fresh weight of male and female adults emerged in Vip3Aa treatment (2.87 mg and 3.86 mg, respectively) did not vary significantly from that of the negative control treatment (2.66 mg, 3.75 mg). However, the time taken by the larvae to complete their development (12.70 days) was significantly extended than that of the negative control (10.21 days). In contrast, the tested life-table parameters of P. japonica were adversely affected when fed on synthetic diet containing boric acid (positive control) indicating experimental fitness to detect adverse effects.ConclusionsOn the basis of the results, it is suggested that GM crops expressing Bt protein (Vip3Aa) are safe for non-target insects such as P. japonica and are compatible with other biological programs for the integrated management of insect pests.

Aedes albopictus life table: environment, food, and age dependence survivorship and reproduction in a tropical area

BackgroundEnvironmental conditions affect the biology of mosquito vectors. Aedes albopictus is a major vector of many important diseases including dengue, Zika, and chikungunya in China. Understanding the development, fecundity, and survivorship of Ae. albopictus mosquitoes in different environmental conditions is beneficial for the implementation of effective vector control measures.MethodsAedes albopictus larval and adult life-table experiments were conducted under natural conditions in indoor, half-shaded, and fully shaded settings, simulating the three major habitat types in Hainan Province, a tropical island in the South China Sea. Temperature, humidity, and light intensity were recorded daily. Larval rearing used habitat water and tap water, with and without additional artificial food. Development time, survivorship, pupation rate, and adult emergence rates were monitored. Adult mosquito survivorship and fecundity were monitored daily and reproductive rates were determined, and age-dependent survivorship and reproduction were analyzed.ResultsThe pupation time and male and female emergence times were significantly shorter in indoor conditions than in shaded and half-shaded conditions for both tap water with added food and habitat water with added food groups. For habitat water with added food, the shaded environment had the lowest pupation rate among the settings. For tap water with added food group, the shaded environment had the lowest pupation rate. The mean survival time of females was 27.3 ± 0.8 days in the indoor condition, which was significantly longer than that in the half-shaded (18.4 ± 0.6 days) and shaded (13.8 ± 1.2 days) conditions. Adult mortality was age-dependent, and the rate of change in mortality with age was not significantly different among different environmental conditions. The mean net replacement rate (R0) of female mosquitoes showed no significant difference among the three conditions, whereas the per capita intrinsic growth rate (r) in the shaded condition was 42.0% and 20.4% higher than that in the indoor and half-shaded conditions, respectively. Female daily egg mass was also age-dependent in all the settings, decaying exponentially with age.ConclusionsOur results imply that half-shaded conditions are likely the best natural condition for adult emergence and female reproduction, and food supply is crucial for larval development and pupation. The results provide new avenues for integrated mosquito management in indoor and outdoor areas, especially in half-shaded areas.Graphical

Sex-specific developmental trajectories in an extremely sexually size dimorphic spider.

Adult body size, development time, and growth rates are components of organismal life histories, which crucially influence fitness and are subject to trade-offs. If selection is sex-specific, male and female developments can eventually lead to different optimal sizes. This can be achieved through developmental plasticity and sex-specific developmental trajectories. Spiders present suitable animals to study differences in developmental plasticity and life history trade-offs between the sexes, because of their pronounced sexual dimorphism. Here, we examine variation in life histories in the extremely sexually size dimorphic African hermit spider (Nephilingis cruentata) reared under standardized laboratory conditions. Females average 70 times greater body mass (and greater body size) at maturity than males, which they achieve by developing longer and growing faster. We find a small to moderate amount of variability in life history traits to be caused by family effects, comprising genetic, maternal, and early common environmental effects, suggesting considerable plasticity in life histories. Remarkably, family effects explain a higher variance in male compared to female life histories, implying that female developmental trajectories may be more responsive to environment. We also find sex differences in life history trade-offs and show that males with longer development times grow larger but exhibit shorter adult longevity. Female developmental time also correlates positively with adult body mass, but the trade-offs between female adult mass, reproduction, and longevity are less clear. We discuss the implications of these findings in the light of evolutionary trade-offs between life history traits.

Heat waves affect an invasive herbivore and its parasitoid differentially with impacts beyond the first generation

AbstractHeat waves are becoming more frequent with climate change, and their impact on lower and higher trophic levels can differ. Higher trophic levels, such as predators and parasitoids, are predicted to be more strongly affected by heat waves than herbivores because they may have smaller thermal windows and because of altered ecological interactions with lower trophic levels. We tested the effects of heat waves of varying intensity (36–42°C), imposed for 4 h during five consecutive days on the egg stage of an invasive herbivore, the brown marmorated stink bug (Halyomorpha halys), and on various developmental stages of its parasitoid,Trissolcus japonicus.Halyomorpha halyseggs had lower hatching success and fewer nymphs emerging with increasing intensity of heat stress, while exposure during the egg and larval stages ofT. japonicusdid not decrease adult emergence rates. Heat waves increased developmental time of parasitoids and decreased adult emergence when pupal stages were exposed. Adult parasitoids experiencing heat stress had lower survival, but their parasitism success overall was not affected. In addition, we detected transgenerational effects, whereas emergence success and the number of adult parasitoids emerging in the second generation declined when the parental generation was exposed to 42°C. Contrary to expectations, the results suggest thatH. halysmay be more sensitive to heat stress thanT. japonicus, at least during early development. Our findings indicate that biological control services provided byT. japonicuscan be maintained in the face of increasing heat wave events and point to the importance of following populations beyond the first generation to better understand the long‐term consequences of heat stress.

Wolbachia promotes successful sex with siblings in the parasitoid Habrobracon hebetor.

Wolbachia are intracellular α-proteobacteria that have a wide distribution among various arthropods and nematodes. They affect the host reproduction favoring their maternal transmission, which sets up a potential conflict in inbreeding situations when the host avoids sexual reproduction preventing inbreeding depression, while Wolbachia pushes it. We used the wasp Habrobracon hebetor to test the hypothesis that Wolbachia modulates inbreeding avoidance behavior and promotes sib mating. Our results showed no obvious pre-copulatory inbreeding avoidance in this wasp. However, H. hebetor showed a strong post-copulatory inbreeding avoidance behavior that resulted in a low fertilization rate of uninfected siblings and therefore high rate of production of male progeny was obtained. We observed higher rates of fertilization success in the Wolbachia-infected lines that resulted in significantly higher female progeny production compared to the uninfected sib mates. Since diploid females are the result of successful fertilization due to haplodiploidy sex determination system in this insect, our results indicate that Wolbachia promoted fertile sib mating in H. hebetor. Interestingly, the rate of adult emergence in the progeny of Wolbachia-infected sib mates were almost similar to the non-sib mate crosses and significantly more than those observed in the uninfected sib mate crosses. Our results support the idea that Wolbachia modulates inbreeding avoidance and promotes sib mating and also mitigates inbreeding depression. By promoting successful sex with siblings and increasing the probability of female progeny, Wolbachia enhances its transmission to the next generation. This is an undescribed effect of Wolbachia on the host reproduction. © 2021 Society of Chemical Industry.

Ingestion Effect of Makisterone A, a Phytoecdysteroid, on Development and Detoxification Enzymes of Tribolium castaneum (Coleoptera: Tenebrionidae)

Worldwide losses of stored and post-harvested products are mainly due to insect attacks. Although conventional pesticides are widely applied to control pest invasions, there has been an increasing pressure to reduce reliance on conventional pesticides in the interests of avoiding health and environmental consequences. In this work, the effect of ingested Makisterone A, which is a phytoecdysteroid, was tested on the major insect pest of stored products, Tribolium castaneum (Herbst). Firstly, the effect of this molecule on post-embryonic development parameters (mortality, pupation and adult emergence) was tested after ingestion at 300, 600, 900 and 1200 ppm. Secondly, the effect of the Makisterone A was also tested on the biochemical parameters (proteins, alpha-amylase, detoxification enzymes). Ingestion of Makisterone A by T. castaneum larvae induced mortality and significantly reduced pupation and adult emergence rates. Our results show that the level of proteins decreases significantly (P < 0.001) in larvae treated with Makisterone A in comparison with the controls in a dose-dependent manner. Protein content was 176.94, 106.72, 93.16 and 39.32 µg/larva, respectively for 300, 600, 900 and 1200 ppm. In addition, a significant inhibition of alpha-amylase activity was also registered. Its activity achieved 131.68 ± 1.7 µg of starch consumed/larva at 1200 ppm. Results also showed that ingestion of Makisterone A decreased the esterase and P-450 monooxygenases activities when used at higher concentration. In contrast, glutathione S-transferase activity increased in a dose dependent manner. The activity reached 273.26 ± 6.4 nanomoles of substrate conjugated/min/mg of protein using Makisterone A at 1200 ppm. All the results showed the bioinsecticidal potential of phytoecdysteroids in control of insect pests of stored products.

Cannibalism and Necrophagy Promote a Resource Loop and Benefit Larval Development in Insects of Temporary Waters.

Simple SummaryThe consumption of conspecific individuals by cannibalism (i.e., the killing and eating of conspecific individuals) and necrophagy (i.e., feeding on dead individuals of the same species) has been documented in several insect species. Selective advantages have been proposed to explain the persistence of these behaviors in natural populations. In this paper, we tested the hypothesis that cannibalism and necrophagy lead to a significant resource loop within an insect cohort, allowing individual survival and development. With this aim, we performed laboratory and semi-field experiments using the tiger mosquito Aedes albopictus. Larval stages of this species develop in small aquatic habitats, such as tree holes and artificial containers. These latter are highly ephemeral habitats, where resources are often scarce and of poor quality (mainly leaf litter, wood, and vegetal detritus). We first estimated the relative rate of cannibalism and necrophagy. Then, we analyzed the effects of cannibalism and necrophagy on larval survival and adult yield. Consistent with our hypothesis, we found that conspecifics consumed about 50% of the initial cohort. Furthermore, conspecific consumption significantly increased the rate of adult emergence and larval survival, which supports that cannibalism and necrophagy can positively affect insect populations in temporary waters.Temporary aquatic habitats are contingent on the allochthonous inputs of plant and animal detritus, whose quality and availability can significantly affect the species developing in these habitats. Although animal detritus (i.e., invertebrate carcasses) is a high-quality food, it is an unpredictable and variable resource. On the contrary, conspecific individuals (dead or alive) are a nutritionally high-quality food source that is always available. In this context, conspecifics consumption, by cannibalism or necrophagy, can be a good strategy to overcome nutrient limitation and allow individual maintenance and development. Here, we tested this hypothesis by using the tiger mosquito Aedes albopictus. By carrying out laboratory and semi-field experiments, we first estimated the relative rate of cannibalism and necrophagy, under different larval densities. Then, we analyzed the effects of cannibalism and necrophagy on larval survival and adult yield. Consistent with our hypothesis, we found that cannibalism and necrophagy occurred under all experimental conditions, and that conspecific consumption had positive effects on individual development, as it significantly increased the rate of adult emergence and larval survival. Interestingly, about 50% of the initial cohort was consumed by conspecifics, suggesting that cannibalism and necrophagy can drive an important resources loop in temporary aquatic habitats.