Egg Development Time Research Articles

Variation in parasitoid adult size is related to host egg size, maternal state and developmental time

AbstractBody size is a characteristic of many animal species that is correlated with many fitness‐related traits. Parasitoids are important biological control agents of pests; larger parasitoids often have greater fitness and enhanced performance. Host size is a major influence on parasitoid size, which has been explored in the important egg parasitoid Anastatus disparis (Hymenoptera: Eupelmidae), a potential biological control agent for several Lepidopteran pests. Here, we found that the body size of A. disparis females increased with increasing host egg size, while host egg size did not significantly affect male size. In addition, both female and male offspring sizes significantly increased with increasing maternal size, and female offspring produced by younger mothers were also larger. Furthermore, the body sizes of both females and males appeared to increase when the total development time from egg to adult eclosion decreased. Male offspring produced by larger females have shorter development times, while female offspring produced by older females have longer development times. Consequently, our results suggested that the effect of maternal status on offspring size may be mediated by influencing development time. In summary, our results indicated that the body size of A. disparis is determined by multiple factors with differing effects on females and males, and our results provide guidance for its effective mass rearing and its performance in the field.

Risk assessment, fitness cost and transcriptome analysis of cyantraniliprole resistance in Spodoptera frugiperda

Spodoptera frugiperda is a notorious invasive pest causing substantial yield losses of crops and has developed resistance to various types of insecticides. In this study, a cyantraniliprole-resistant strain, SfCYAN-R, was obtained from a susceptible strain, SfCYAN-S, after 13 generations of selection with cyantraniliprole. The fitness cost in SfCYAN-R strain was evaluated, and the putative resistance-related genes were explored by RNA-seq analysis. The results showed that SfCYAN-R strain developed 23.97-fold resistance to cyantraniliprole with the realistic heritability of 0.127. The development time of eggs, larvae, prepupae and pupae in SfCYAN-R strain was significantly prolonged than that in SfCYAN-S strain, but no difference in pupation rate, emergence rate and female fecundity was observed between SfCYAN-R and SfCYAN-S strains. Comparative gene expression analysis between SfCYAN-R and SfCYAN-S strains identified 776 significant differentially expressed genes (DEGs), among which several DEGs associated with xenobiotic metabolism were upregulated in SfCYAN-R strain. These results provide insights into the resistance mechanisms of cyantraniliprole and would be helpful for resistance management of S. frugiperda.

Biology of Euwallacea interjectus, an emerging poplar pest, reared on an ambrosia beetle artificial diet and medium of fungal symbiont.

Euwallacea interjectus, a recently discovered pest in poplar plantations, poses a significant economic threat due to its role in causing widespread tree mortality. This pest's cryptic behaviour has hindered research and control efforts, making laboratory rearing a valuable tool for studying its development and biology. We investigated the development period and biological characteristics of E. interjectus using artificial diets and fungal medium. Our findings revealed that the development time for eggs, larvae, and pupae averages approximately 6, 18, and 6 days, respectively. Notably, first and second instar larvae displayed peak moulting periods at 3.45 ± 0.64 SD and 7.92 ± 1.77 SD days, respectively. Furthermore, we measured head capsule widths of postmolt larvae, yielding values of 318.02 ± 7.38 SD μm for first-instar larvae, 403.01 ± 11.08 SD μm for second-instar larvae, and 549.54 ± 20.74 SD μm for third-instar larvae. Our research also uncovered a positive correlation between the number of progeny (eggs, larvae, pupae, and adults) and the mean length of the gallery system. Interestingly, the haplodiploid reproductive strategy did not significantly affect the number of offspring produced by the foundress. Additionally, we observed that foundresses displayed higher fecundity when subjected to nutrient-rich diets as compared to nutrient-poor diets. Our results will deepen our understanding of the biology of E. interjectus and provide criteria for larval instar classification. Additionally, managing nutrient availability within the colony could be considered a viable approach to regulating population size.

Combining temperature-dependent life table data into Insect Life Cycle Model to forecast fall armyworm Spodoptera frugiperda (JE Smith) distribution in maize agro-ecological zones in Africa.

The fall armyworm (FAW), Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), an invasive agricultural pest, has significantly impacted crop yields across Africa. This study investigated the relationship between temperature and FAW life history traits, employing life cycle modeling at temperatures of 20, 25, 28, 30, and 32°C. The development time for eggs, larvae, and pupae varied from 0-3 days, 10-18 days, and 7-16 days, respectively. The optimal temperature range for immature stage survival and female fecundity was identified as 21-25°C, with the intrinsic rate of increase (rm) and gross reproductive rate (GRR) peaking at 25-28°C. Model validation confirmed the accuracy of these findings. The research further projected the Establishment Risk Index (ERI), Activity Index (AI), and Generation Index (GI) for FAW under current and future climates (2050 and 2070) using RCP 2.6 and RCP 8.5 scenarios. Results indicate that RCP 2.6 leads to a reduction in high-risk FAW areas, particularly in central Africa. Conversely, RCP 8.5 suggests an increase in areas conducive to FAW activity. These findings highlight the impact of climate policy on pest dynamics and the importance of incorporating climatic factors into pest management strategies. The study predicts a potential decrease in FAW prevalence in West Africa by 2070 under aggressive climate mitigation, providing a basis for future FAW management approaches.

Temperature has an overriding role compared to photoperiod in regulating the seasonal timing of winter moth egg hatching.

To accurately predict species' phenology under climate change, we need to gain a detailed mechanistic understanding of how different environmental cues interact to produce the seasonal timing response. In the winter moth (Operophtera brumata), seasonal timing of egg hatching is strongly affected by ambient temperature and has been under strong climate change-induced selection over the past 25years. However, it is unclear whether photoperiod received at the egg stage also influences timing of egg hatching. Here, we investigated the relative contribution of photoperiod and temperature in regulating winter moth egg development using two split-brood experiments. We experimentally shifted the photoperiod eggs received by 2-4weeks compared to the actual calendar date and measured the timing of egg hatching, both at a constant temperature and in combination with two naturally changing temperature treatments - mimicking a cold and a warm year. We found an eight-fold larger effect of temperature compared to photoperiod on egg development time. Moreover, the very small photoperiod effects we found were outweighed by both between- and within-clutch variation in egg development time. Thus, we conclude that photoperiod received at the egg stage does likely not play a substantial role in regulating the seasonal timing of egg hatching in the winter moth. These insights into the regulatory mechanism of seasonal timing could have important implications for predicting insect climate change adaptation, as we might expect different targets of selection depending on the relative contribution of different environmental cues.

Simultaneous warming and acidification limit population fitness and reveal phenotype costs for a marine copepod.

Phenotypic plasticity and evolutionary adaptation allow populations to cope with global change, but limits and costs to adaptation under multiple stressors are insufficiently understood. We reared a foundational copepod species, Acartia hudsonica, under ambient (AM), ocean warming (OW), ocean acidification (OA), and combined ocean warming and acidification (OWA) conditions for 11 generations (approx. 1 year) and measured population fitness (net reproductive rate) derived from six life-history traits (egg production, hatching success, survival, development time, body size and sex ratio). Copepods under OW and OWA exhibited an initial approximately 40% fitness decline relative to AM, but fully recovered within four generations, consistent with an adaptive response and demonstrating synergy between stressors. At generation 11, however, fitness was approximately 24% lower for OWA compared with the AM lineage, consistent with the cost of producing OWA-adapted phenotypes. Fitness of the OWA lineage was not affected by reversal to AM or low food environments, indicating sustained phenotypic plasticity. These results mimic those of a congener, Acartia tonsa, while additionally suggesting that synergistic effects of simultaneous stressors exert costs that limit fitness recovery but can sustain plasticity. Thus, even when closely related species experience similar stressors, species-specific costs shape their unique adaptive responses.

Development of a Phenology Model for Egg Hatching of Walking-Stick Insect, Ramulus mikado (Phasmatodea: Phasmatidae) in Korea

The walking-stick insect Ramulus mikado is occasionally considered a forest pest, as its mass occurrence can cause severe defoliation. It overwinters as eggs on the ground surface, and the hatched nymphs climb up to the host trees in spring. In this study, temperature-dependent development experiments were performed on R. mikado eggs under three constant temperatures (23.3, 28.3, and 29.2 °C) to extend the previously reported thermal response. The development times of eggs collected in summer and winter were also compared to investigate how development status is influenced by the seasons. The lower and upper developmental thresholds and thermal constants of R. mikado eggs were estimated to be 6.1 °C, 29.2 °C, and 1707.8 DD, respectively. The starting point for effective temperature effects on the eggs was estimated to be 1 August, based on the results of the experiment on field-collected eggs. A phenology model was constructed by using a development completion model scaled by the thermal constant, with a starting point of degree-day accumulation. The model showed good agreement, with a deviation of 3.2 ± 2.95 days between prediction and observation. The developed phenology model is useful for determining the appropriate timing for management decision-making regarding this insect.

Effects of Population Density on Survival, Development Time, Fecundity and Hatchability of <i>Samia cynthia ricini</i> Boisduval

Samia cynthia ricini Boisduval Lepidoptera:Saturniidae is a lepidopteran insect that has a gregarious behaviour during their larval stage. This research aimed to determine the minimum population limit of larvae that can support the survival of S. c. ricini by observing the development time, fecundity, and hatchability of eggs produced by adult moths under different larval densities rearing conditions. The research was conducted by observing the lifecycle and development of S. c. ricini at different population densities. The results showed that density had effect on the development time of S. c. ricini egg only. Population density also affects the survival and adult fecundity of S. c. ricini. A density of 30 is the minimum population required to support the success of S. c. ricini’slife. Samia cynthia ricini reared at this density had the highest survival rate, faster egg development time, heavier cocoon shell weight and highest fecundity.

Individual and binary exposure to nanoscales of silver, titanium dioxide, and silicon dioxide alters viability, growth, and reproductive system: Hidden indices to re-establish artemia as a toxicological model in saline waters

This study evaluated and compared the individual and combined toxicity of AgNPs, TiO2NPs, and SiO2NPs to life cycle of A. salina. To this end, both stability and toxicity of AgNPs were determined in the presence of TiO2NPs and SiO2NPs. The colloidal stability of AgNPs decreased in the presence of the other two NPs, especially SiO2NPs. AgNPs displayed acute toxicity to A. salina, whereas SiO2NPs and TiO2NPs chronically induced toxicity in a concentration- and time-dependent manner during 28-day exposure. The experimental NPs significantly decreased the weight and length of A. salina and induced reproductive toxicity through perturbation in first brood timespan, sexual maturity, egg development time, egg pouch area, offspring quality, and fecundity. Exposure to AgNPs shifted the mode of reproduction in brine shrimp from ovoviviparity to oviparity, and also co-presence of AgNPs with SiO2NPs or TiO2NPs caused infertility. Generally, their individual toxicity was in order of AgNPs > TiO2NPs > SiO2NPs, and binary exposure to AgNPs-SiO2NPs appear to be more threatening than AgNPs-TiO2NPs to A. salina. Together, this study highlights that these nanoparticles could disrupt reproductive health of A. salina and lead to alterations in population dynamics and aquatic ecosystem balance.

Multivariate evaluation of cold tolerance in domestic and foreign populations for addressing climate mismatch in biological control of Alternanthera philoxeroides in the USA

AbstractLack of successful biological control of alligatorweed, Alternanthera philoxeroides (Mart.) Griseb. (Amaranthaceae), by Agasicles hygrophila Selman & Vogt (Coleoptera: Chrysomelidae) in the USA is an emerging problem as A. philoxeroides expands into temperate climates due to poor cold tolerance of the beetles. Sourcing climatically suited biotypes of biological control agents is traditionally done through foreign exploration into their native range; however, surveying introduced populations may provide a cost‐effective and regulatory‐friendly alternative. To compare foreign biotypes to those established in the USA, two populations of A. hygrophila were collected from the coolest extent of their range in South America, and two populations were collected from stable populations in the southeastern USA. For comparing cold tolerance among introduced populations, eight populations were collected from across a climatic gradient. For all populations, cold tolerance was measured as a function of supercooling point, critical thermal minimum (CTmin), chill coma, and temperature‐dependent survival and development of eggs and larvae. Results of cold‐tolerance measures for North American populations were subjected to principal component analysis (PCA) to reduce dimensionality and detect trends in cold tolerance among populations. For foreign and locally collected A. hygrophila, South American populations were significantly more cold tolerant as measured by CTmin (Δ1.98 °C), chill coma (Δ1.95 °C), larval survival (Δ35.0%), and development time of eggs (24.7% faster) and larvae (17.4% faster) at 15 °C. Comparisons among North American populations found significant differences in cold tolerance across populations; however, results were less consistent than those observed for foreign populations. The first principal component (PC) explained 43.0% of variation in cold‐tolerance metrics and was strongly related to mean temperature of the coldest quarter. The use of a multivariate approach to evaluate and compare cold‐tolerance phenotypes provides strong evidence of local adaptation in introduced populations of A. hygrophila. However, South American populations may still provide the best chance for control of A. philoxeroides in northern infestations.

Marked Effects of Larval Salt Exposure on the Life History and Gut Microbiota of the Malaria Vector Anopheles merus (Diptera: Culicidae).

Anopheles merus can breed in a range of saltwater concentrations. The consequences of this ability on the life history of adult An. merus are poorly understood. This study examined the effects of exposure to 0, 2.1875, 4.375, 8.75, and 17.5 g/L of sodium chloride on An. merus. The effects on larval development, adult longevity, fertility, and fecundity, as well as deltamethrin tolerance were examined. The effect of larval salt exposure on the expression of defensin-1 in adults was examined by quantitative Real-Time PCR. Finally, the effect of the larval salt concentration on microbial dynamics was assessed by 16S Next Generation Sequencing. High concentrations of saltwater increased larval development time and number of eggs laid, as well as deltamethrin tolerance. Larval exposure to salt also reduced the expression of defensin-1. The exposure also had a significant effect on microbial diversity in larvae and adults. The diversity of larvae decreased once adults emerged. Salt-tolerant bacterial genera predominated in larvae but were absent in adults. High salt concentrations resulted in greater abundance of Plasmodium-protective genera in adults. Although this study was conducted on a laboratory strain of An. merus, these data suggest that osmoregulation has a significant effect on the life history of the species with potential epidemiological consequences.

Effects of cadmium ingestion on reproduction and maternal egg care in the European earwig

A growing number of studies show that anthropization can alter the behaviour, survival, physiology, cognition and reproduction of many animal species. However, its impact on parental care, a common behaviour where even subtle changes can have dramatic effects on the viability of future generations and thereby jeopardize population dynamics, remains surprisingly unclear. Here, we studied the effects of exposure to cadmium, a highly toxic chemical pollutant widely distributed in the trophic chain, on egg production and maternal egg care in the European earwig, Forficula auricularia . We fed 200 females with food containing cadmium at five different concentrations for several weeks, and then quantified the number of eggs produced, the expression of six forms of egg care and three forms of noncare behaviours, as well as maternal survival and egg development. In contrast to most results reported in other animal species, we found no evidence that ingestion of even substantial doses of cadmium affects egg production or maternal egg care in the form of grooming, antennation, displacement, gathering, defence or retrieval. Moreover, it neither affected maternal exploration, inactivity or self-grooming behaviours, nor egg development time, hatching rate or juvenile weight. Overall, these results reveal that egg care is resilient to environmental cadmium pollution in earwigs and suggest that females possess efficient and fast-acting physiological processes that help them reduce their sensitivity to heavy metal contamination. More generally, our findings may suggest that selection pressures associated with the necessity to express egg care has directly or indirectly selected for higher resistance/tolerance against certain chemical pollution, and thus that species with parental care could be more resilient in the face of increasing levels of anthropogenic pollution. • Egg care is an essential behaviour to ensure the viability of future generations. • Cadmium is highly toxic to organisms and affects numerous fitness-related traits. • We tested the effects of cadmium on egg care and reproduction in earwig females. • We found that egg care and female reproduction were independent of cadmium exposure. • The critical importance of egg care could explain the robustness of this behaviour.

Development of Cigarette beetle [Lasioderma serricorne (Coleoptera :Anobiidae)] on spice plants and wheat flour

In this study, the development of Lasioderma serricorne (F.) (Coleoptera: Anobiidae) was investigated on five different foods (Mentha piperita, Thymus vulgaris, Salvia officinalis, Rosmarinus, officinalis and flour). Trials were carried out at a temperature of 28±2°C and 70-75% relative humidity. Effects of foods on development adult longevity and egg hatching ratio of Lasioderma serricorne were investigated. As a result, all of the Lasioderma serricorne larvae left on the Rosmarinus officinalis plant have not completed their development and died. The shortest larval development time was in flour (37.35 days) and the longest in Mentha piperita (62.96 days). The shortest Pupal development time was seen in Salvia officinalis (4 days), while the longest was seen in Thymus vulgaris (4,42 days). Mentha piperita (10,50 days) had the shortest adult longevity and was the longest flour (15,5 days). When the egg development time was examined, it was seen that the shortest time was in Thymus vulgarris (5,42 days) and the longest time was in flour (5,97 days). The rate of larvae that completed its development was highest in flour (92%) and lowest in Salvia officinalis (5%). The rate of pupae that completed its development was highest in flour (80,30%) and lowest in Salvia officinalis (37.50%). In the percentages of hatched eggs, it was observed that the lowest opening was in thyme with 56.27% and the highest opening was in flour with 88.89 %.

Characterizing the Flow Regime in Brook Trout Incubation Habitats and Implications for Management in a Hydro‐Regulated River

AbstractThe operation of dams, diversions, and power generation facilities unavoidably influence the ecological function of rivers. We evaluated vertical and horizontal hydraulic gradients and subsequent water temperature changes in the hyporheic zone of a spawning area for Brook Trout Salvelinus fontinalis in a managed Lake Superior tributary in Ontario, then conducted a laboratory‐based experiment to show the impact of cold shock during incubation on the timing of larval emergence and survival. Upwelling groundwater was observed at the spawning area during the monitoring period (October 28, 2016, to January 11, 2017); hyporheic water temperatures remained above 3.7°C, whereas ambient river temperature above the substrate fell to 1.5°C until water was released from the upstream control dam. After the release event, water level increased by 0.9 m over the spawning area, and within 24 h, vertical and horizontal flow gradients were reversed in the hyporheic zone; downwelling conditions were observed for 30 h between surface and hyporheic water 1.8 m below substrate, and hyporheic water temperature decreased in unison. Hyporheic temperatures at shallow inshore sites fell below 1°C for more than 53 h. In the laboratory, applying a worst‐case scenario of dam‐induced cold shock on Brook Trout redds using historic monitoring records (i.e., <1.0°C for 40 h), we found no appreciable effect on survival and development timing of incubating Brook Trout eggs compared with a control group. Survival from fertilization to hatching was high for both treatment and control groups (>90%) and lower from fertilization to emergence (55%). Overall, our results suggest that standard winter operating procedures on a Lake Superior tributary had little impact on Brook Trout egg survival and development time to hatching and emergence; however, our findings also suggest that staged winter discharges would lessen the reversal of flow in the hyporheic zone and the magnitude of temperature changes experienced at Brook Trout redds.

Invasive Widow Spiders Perform Differently at Low Temperatures from Conspecifics from the Native Range.

Temperature challenges are one of the leading abiotic causes of success or failure of non-native species in a novel environment, and this is particularly true for low temperatures. Establishing and reproducing in a novel thermal environment can alter survival, behavior, and traits related to fitness. It has been proposed that plasticity or adaptation of thermal tolerance may allow an introduced species to thrive, or that successful invaders may be those with a thermal breadth in their native habitat that encompasses their new environment. Here, we tested these hypotheses using native and invasive populations of Australian redback spiders (Latrodectus hasselti). We measured how exposure to temperatures common to invasive and native range habitats (exposure to 15 and 25°C, respectively) affected behavioral and life-history traits and trade-offs that may underlie fitness in an invasive population detected in 1995 in Japan and a native population from Australia. We found that the critical thermal minimum (CTmin) was higher in the invasive population from Japan than in the native population, but critical thermal maximum (CTmax) did not differ between populations. Compared to the invasive population, eggs from the native population had a longer development time and lower hatching success at 15°C. Both populations performed equally well at 25°C, as measured by egg development time and hatching success. Invasive juveniles tested at 15°C were faster to explore a novel environment and bolder compared to those tested at 25°C. In comparison, the native population showed faster average exploration, with no differences in boldness or exploration at the two development or testing temperatures. Overall, L. hasselti from Japan maintained hatching success and development across a wider temperature range than the native population, indicating greater thermal breadth and higher behavioral plasticity. These results support the importance of plasticity in thermal tolerance and behavior for a successful invasion under novel environmental temperatures.

Development of two common dragonfly species with diverging occupancy trends

The two sibling and syntopic odonate species Sympetrum striolatum and Sympetrum vulgatum are common and widespread in Central Europe. While S. striolatum has strong positive population trends, declines of S. vulgatum are observed. The aim of this study was to identify possible drivers of these diverging trends. We presumed that differences in egg development may lead to differences in survival until hatching. First, eggs laid in non-permanent or shrinking waterbodies may suffer of increasing drought periods. Second, differences in developement may cause increased size-mediated intraguild predation, a common cause of reduced survival in odonate larvae. Egg development time and hatching rates were recorded of eleven egg clutches of S. vulgatum and ten clutches of S. striolatum under simulated drought vs. water and direct vs. delayed development treatments. Hatching rates were reduced under drought conditions, and particularly so in S. vulgatum. We did not observe obligate winter diapause in any of the egg clutches. But, S. vulgatum varied widely in development between clutches, while the eggs of S. striolatum developed much faster and hatched highly synchronously. This would provide S. striolatum with a temporal advantage that may lead to a size-advantage over most S. vulgatum. We also found that S. vulgatum grew faster. Faster larval growth would only compensate for those S. vulgatum with fast egg development. The current population trends may be partly attributed to lowered survival of S. vulgatum under drought and by phenological and, thus, size benefits of S. striolatum.Implications for insect conservationOur results show that population dynamics of two closely related dragonfly species can be explained by climatically induced changes in their interactions. Understanding the causes and processes of behavioural changes resulting in differing population trends is fundamental for the protection of species.

EPPO Datasheet: Naupactus xanthographus

EPPO Datasheet: <i>Naupactus xanthographus</i>

Hydrotimetes natans as a suitable biological control agent for the invasive weed Cabomba caroliniana

The aquatic macrophyte Cabomba caroliniana A. Gray is a major invasive weed in Australia and several other countries. A classical biological control program was initiated in Australia in 2003 and native range explorations in Argentina that year led to the discovery of the aquatic weevil Hydrotimetes natans Kolbe feeding on C. caroliniana, making it the first, and so far, only potential biological control agent for the weed. However, the program was discontinued because the largely unknown biology had made rearing of H. natans difficult under quarantine laboratory conditions. We report here key aspects of the biology and reproductive behaviour of H. natans that provided significant insights to successfully establish a laboratory colony when the program was restarted in 2016. In addition, we studied the physiological host range of H. natans and determined its risks to 15 non-target plant species. The preoviposition period of H. natans was 6.50 ± 0.85 days, and the development times of eggs and pupae were 7.65 ± 0.86 and 14.27 ± 0.51 days, respectively. Egg to adult development time was 46.52 ± 0.82 days with a larval development time of 25–27 days. A single female laid 123.13 ± 23.03 eggs in 24 weeks under non-limiting laboratory conditions. Oviposition was intermittent and age-dependent with 75% eggs oviposited within 8.54 weeks after adult eclosion; percent viability of these eggs was 55.62 ± 4.61. Females oviposited mostly on the apical tips followed by on the first few nodes from the tip. Adults survived a maximum of 521 days with a mean longevity of 235.16 ± 21.16 days and females remained reproductive for 211.00 ± 35.05 days. Field surveys and laboratory host-specificity studies demonstrated H. natans is adequately host-specific to C. caroliniana. No non-target effects were observed on Nymphaea, Victoria and Trithuria species. Brasenia schreberi indicated the possibility of lifecycle completion by H. natans in choice and no-choice trials but did not sustain a population in continuation trials. The risks to B. schreberi were deemed negligible and H. natans was approved for release in Australia.

Effect of temperature on the development of the free-living stages of horse cyathostomins.

Cyathostomins are considered as the most prevalent and pathogenic parasites of grazing horses. The development on pastures of the free-living stages of these gastrointestinal worms is particularly influenced by outdoor temperature. Understanding the bionomics of free-living stages is an important prerequisite to implement mathematical models designed to assess the parasitic risk for grazing equids. The aim of this study was to assess the effect of 3 constant temperatures under laboratory conditions (10±1°C, 23±2°C, 30±2°C) and one fluctuating temperature under outdoor conditions (mean: 17±4°C) on the minimum time taken by cyathostomin eggs to develop into first/second stage larvae (L1/L2) then into infective third stage larvae (L3) in horse faeces. According to the temperatures, the minimum time taken by eggs to develop into L1/L2 was between 1 and 3days and into L3 between 4 and 22days. At 10°C, the development time of eggs into L3 was the longest and at 30°C the fastest. The results were consistent with historically available data and their compilation should lead to the improvement of parameterised models assessing the parasitic risk period in grazing equids.

Damselfly eggs alter their development rate in the presence of an invasive alien cue but not a native predator cue.

Biological invasions are a serious problem in natural ecosystems. Local species that are potential prey of invasive alien predators can be threatened by their inability to recognize invasive predator cues. Such an inability of prey to recognize the presence of the predator supports the naïve prey hypothesis. We exposed eggs of a damselfly, Ischnura elegans, to four treatments: water with no predator cue (control), water with a native predator cue (perch), water with an invasive alien predator cue (spinycheek crayfish) that is present in the damselfly sampling site, and water with an invasive alien predator cue (signal crayfish) that is absent in the damselfly sampling site but is expected to invade it. We measured egg development time, mortality between ovipositing and hatching, and hatching synchrony. Eggs took longer to develop in the signal crayfish group (however, in this group, we also observed high green algae growth), and there was a trend of shorter egg development time in the spinycheek crayfish group than in the control group. There was no difference in egg development time between the perch and the control group. Neither egg mortality nor hatching synchrony differed between groups. We suggest that egg response to signal crayfish could be a general stress reaction to an unfamiliar cue or an artifact due to algae development in this group. The egg response to the spinycheek crayfish cue could be caused by the predation of crayfish on damselfly eggs in nature. The lack of egg response to the perch cue could be caused by perch predation on damselfly larvae rather than on eggs. Such differences in egg responses to alternative predator cues can have important implications for understanding how this group of insects responds to biological invasions, starting from the egg stage.