Insect Growth Rates Research Articles

Time-course analysis system for leaf feeding marks reveals effects of Arabidopsis trichomes on insect herbivore feeding behavior.

Bioassay with an insect herbivore is a common approach to studying plant defense. While measuring insect growth rate as a negative indicator of plant defense levels is simple and straightforward, analysing more detailed feeding behavior parameters of insects, such as feeding rates, leaf area consumed per feeding event, intervals between feeding events, and spatio-temporal patterns of feeding sites on leaves, is more informative. However, such observations are generally time consuming and labor-intensive. Here, we provide a semi-automated system for quantifying feeding behavior parameters of insects feeding on plant leaves. Automated photo scanners record the time-course development of feeding marks on leaves. An image analysis pipeline processes the scanned images and extracts leaf area. By analysing changes in leaf area over time, it detects insect feeding events and calculates the leaf area consumed during each feeding event, providing quantitative parameters of the feeding behavior of insects. In addition, it visualizes spatio-temporal changes in feeding sites, providing a measure of the complex behavior of insects on leaves. Using this analysis pipeline, we demonstrate that Arabidopsis trichomes reduce insect feeding rate, but not feeding duration or intervals between feeding events. Our image acquisition system requires only a photo scanner and a laptop computer and does not require any specialized equipment. The analysis software is provided as an ImageJ macro and R package and is available at no cost. Taken together, our work provides a scalable method for quantitative assessment of the feeding behavior of insects on leaves, facilitating understanding of plant defense mechanisms.

Feeding Activity of Heliotis armigera Hubner Larvae on Food Formulated with Ethanol Extracts of Bitter Melon Leaves (Momordica charantia L.), Galangal Leaves (Lactuna indica L.) and Adjuvant Agrestic

The research on the Feeding Activity of Heliotis armigera Hubner larvae on food formulated with ethanol extracts of bitter melon leaves (Momordica charantia L.), galangal leaves (Lactuna indica L.) and adjuvant agrestic has been conducted. This study used the ratio formulation of bitter melon and galangal (1:1, 1:2, 2:1), 1% adtjuvan agristik. The feeding activity was observed using the feeding method with several concentrations (0.00, 0.58, 1.16, 1.74, 2.32, 2.92) and 15 larvae for iterations using a completely randomized design (CRD). The data from the observations were analyzed using variance; if there were differences, it would proceed to the Duncan test of 5%. Insect feeding activity is influenced by food containing concentrations of 1.16% - 2.92% of a formulation (1:1, 1:2, 2:1) of bitter melon leaf extract, galangal leaf extract, and 1% agrestic adjuvant, leading to a decrease in insect growth rate (RGR). The insect's feeding ability (RCR), ability to convert consumed food into usable nutrients (ECI), and ability to digest food and utilize it (ECD) are also reduced. Conversely, the ability to digest insect food (AD) is increased. The best formulation and concentration are (2:1) and (1.74%).

MODELING THE EFFECTS OF INSECTICIDES ON CROP PRODUCTION IN THE PRESENCE OF INSECT POPULATION

In this research work, a nonlinear mathematical model is proposed and analyzed to study the adverse effects of insects on agricultural productivity by controlling the insect population using insecticides. In the model formulation, it is assumed that agricultural crops grow logistically and the growth rate of insects wholly depends on agricultural crops with Holling type-II functional response. It is further assumed that insects uptake insecticides; thus, the amount of insecticides decreases at a rate proportional to its amount and the density of insect population, and the growth rate of insect population decrease in the same proportion. The feasibility of all non-negative equilibria and their stability properties are discussed. Stability analysis specifies that agricultural crop consumption rate destabilizes the system; however, the spraying rate of insecticides stabilizes the system. The conditions for the existence of pitchfork and Hopf-bifurcation are derived. Considering the spraying rate of insecticides as time-dependent, we have also discussed the optimal control strategy to minimize both insect density and the associated cost. The numerical simulation validates the analytical findings.

Model applicability to predict growth rate of insects throughout storage of corn grain (Zea mays L.)

Insect pest infestation in stored grains can cause several losses during storage, in addition to promoting the spread of fungi, changing the temperature of the grain mass, and reducing the value of the final product. Knowing the behavior of these insect pests and how they reproduce in the grain mass is essential to design more efficient control strategies and ensure a quality final product. Thus, this work aimed to accomplish modeling and simulation of the population growth of insects Rhyzopertha dominica, Sitophilus oryzae, Oryzaephilus surinamensis and Tribolium castaneum throughout the storage of corn grain, using data retrieved from digital sensors of temperature installed in three Brazilian storage facilities in different regions. Data were collected through managing system CERES (company Procer Automação e Sistemas) and retrieved from 1st of July to 29th September 2019. In each one of the facilities, a silo equipped with the aforementioned sensors was used. Mean weekly values of temperature of the grain mass and the intergranular relative humidity were used, calculated using the Modified Henderson equation. The silos evaluated in facilities 1, 2, and 3 have a static capacity of 2,100; 6,304, and 93 tones, respectively, considering soybean with a bulk density of 750 kg m-3. Higher growth rates of all assessed species were observed for the storage facility number 2; and lowest values for storage facility number 1. Storage facilities that presented a higher potential for the growth rate of insects are subjected to elevated levels of insect populations throughout time.

Fruitful female fecundity after feeding Gryllodes sigillatus (Orthoptera: Gryllidae) royal jelly

Abstract Dietary honey bee royal jelly increases insect growth rates and adult body size. Royal jelly as a dietary supplement could enhance mass insect production by increasing the body size of mass-reared model species. To determine the effect of royal jelly on a cricket species, Gryllodes sigillatus Walker (Orthoptera: Gryllidae), farmed for human consumption, we ran two experiments. We tested the dose-dependent response of G. sigillatus to royal jelly using a range of diets across 0–30% w/w royal jelly. We also measured the individual-level life history responses to royal jelly over time by individually rearing G. sigillatus nymphs on two separate diets: half were fed a commercial cricket diet, and half were fed the same diet mixed with 15% w/w fresh royal jelly. We found sex-dependent effects: females fed the royal jelly diet were 30% heavier, and this effect was driven by significantly longer abdomens containing 67% more eggs compared to those fed the standard diet. Female mass was optimised at approximately 17% w/w royal jelly. Our results reveal that although a royal jelly dietary supplement can increase the yield of mass-reared insects, the life history responses are species and sex specific.

Local and sub-basin effects of timber harvests on stream macroinvertebrates in Hinkle Creek watershed

We studied the impacts of clear cut timber harvest over six-years, focusing on aquatic macroinvertebrate response using a BACI design. Data were collected before and after logging throughout a stream network to examine both local and downstream effects of upstream treatments. Sites were located in fishless headwater tributaries, fish-bearing tributaries and main stems in Hinkle Creek’s north fork (reference) and south fork (sequentially harvested) where benthic macroinvertebrates (from 2004 to 2009) and emergent insects (in 2005–2007 and 2009) were sampled. Pre-harvest (2004–2005) benthic macroinvertebrate composition was similar across sub-basins, with distinct longitudinal differences from tributaries to the main stems. At clear cut sites in fishless tributaries, benthic macroinvertebrate densities and percent Chironomidae increased, while taxa richness decreased, and these effects remained consistent for four years after the first harvest; aquatic insect emergence rates were also significantly higher in harvested v. reference fishless tributaries. No downstream macroinvertebrate responses were detected after the first harvest event. Following main stem harvest, confounded by a dam-break flood in December 2008, responses at main stem harvested sites were consistent with the localized responses observed in fishless tributaries, except benthic densities did not increase. While strong differences persisted among macroinvertebrates along the longitudinal gradient in the reference sub-basin, localized decreases in taxa richness and increased proportional contributions of generally disturbance tolerant chironomid midges among harvested sites resulted in altering the structure of invertebrate communities along the stream continuum. We conclude that additive effects of localized changes to instream resources along the stream continuum following successive harvest activities should be considered in plans for basin-wide timber harvests.

The implication of morphometrics and growth rate of dipteran flies in forensic entomotoxicology research: a review.

Forensic entomotoxicology integrates toxicology into forensic entomology to estimate minimum postmortem interval (PMImin) and circumstances of death where toxicants and poisonous substances are the suspected cause of death. Forensic entomotoxicology not only confirms the presence of toxicants in insects feeding off a cadaver but also studies its effect on the bio-morphometry and growth rate of insects. This review article highlights the effects of various toxicants on forensically important species of dipteran flies. It also discusses the parameters that may affect accuracy in estimation of time since death. The bio-physical effects of toxicants (excluding the analytical approach for qualitative detection) would help understand the trends in forensic entomotoxicological research worldwide.

Plant derived powders as alternatives for Sitophilus oryzae L. (Coleoptera: Curculionidae) control in stored maize grains

Maize is the major staple food in Africa. In developing countries, post-harvest losses due to insect pests are up to 40% of total production. Inert powders can be alternative tools in integrated pest management programs of stored cereals. The aim of this study was to assess the efficacy of ashes from cashew (Anacardium occidentale) branches, charcoal powder, dried and milled Eucalyptus citriodora leaves, and diatomaceous earth (standard check), for Sitophilus oryzae control on stored maize grains. The experimental design was completely randomized with 11 treatments and 4 replications. Insect introduction was carried out immediately after treatment application and at 30 and 60 days after. The mortality assessment was performed by counting the dead insects at 10 and 20 days after each infestation. The emergence of S. oryzae adults was also assessed at three different times. The germination of treated grains was also evaluated. Data analysis was performed on the SISVAR statistical package. Diatomaceous earth showed maximum control efficiency (73.75%) at 10-day evaluation, reaching total control at a 20-day evaluation. The remaining treatment control efficiency was below 50% in all concentrations and evaluations. The lowest insect emergence rates were observed in grains treated with diatomaceous earth or charcoal powder, which were more efficient than cashew ashes, Eucalyptus citriodora, and untreated control. There was no significant effect of the tested products on seed germination so, they can be used in smallholder farmers' grain storage. The results allow us to affirm that Eucalyptus citriodora charcoal powder, and cashew ashes can be used to reduce Sitophilus oryzae damage in traditional agricultural systems. Considering the reduction in the Sitophilus oryzae progeny, the potential use of charcoal powder should be considered, given the efficiency compared to that of the diatomaceous earth. Thus, the plant-derived products tested in this study has the potential to be used in the integrated management of Sitophilus oryzae in stored products. Key words: Ash, Charcoal, Diatomaceous earth, inert, dust, maize, storage, pest

Dietary fatty acids of spiders reveal spatial and temporal variations in aquatic-terrestrial linkages

Stream and riparian food webs can be strongly linked by inputs of aquatic emergent insect prey to terrestrial predators. However, quantifying these linkages and understanding how they vary in time and space is challenging. We investigated the dynamic width of a riverine trophic subsidy zone by determining the relationship between perpendicular distance from a river and dietary contributions of aquatic insect prey to web-building spiders' diets. To assess this relationship, riparian web-building spiders at two river sites were sampled during four seasons and analysed for the fatty acids 16:0, 16:1ω7 and 20:5ω3, their total ω3-fatty acid content and their ω3:ω6 ratio to evaluate trophic subsidies reaching them from an adjacent river. River-derived fatty acids generally declined with increased distance from the river, indicating a diffusion of aquatically derived subsidies into the riparian zone. While the river was only 16 m wide at its broadest, river-derived trophic subsidies were detected up to four times that distance from the river edge. Spiders at a downstream section of the river, characterised by generally higher emergence rates of aquatic insects, contained higher proportions of aquatic indicator fatty acids compared with spiders located upstream, where emergence rates were lower. Similarly, proportions of aquatic indicator fatty acids in spiders were lowest during winter when aquatic insect emergence rates were lowest. The fatty acid 20:5ω3 (eicosapentaenoic acid; EPA) held the best promise as a biomarker of aquatic-derived tropic subsidies and could be developed as a useful tool for riparian research and management.

Damage potential of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) on wheat grains stored in hermetic and non-hermetic storage bags

Post-harvest storage of wheat in grain storage bags is commonly adopted practice in many developing countries, which offers a viable chemical-free approach to control storage insects. The damage potential of Tribolium castaneum in wheat grains stored in different storage bags at various storage periods was studied. A highly significant effect (P < 0.01) of the storage bags and storage periods was observed in variables measured (insect growth rate, damaged grains, grain weight loss and weight of insect feeding residues). The maximum mean insect growth rate (85.20 ± 2.80), percent damaged wheat grains (73.24 ± 0.17%), percent grain weight loss (21.14 ± 0.21%) and weight of insect feeding residues (2.15 ± 0.01 g) were recorded in wheat grains stored in cotton cloth bag at 150 d, whereas minimum mean insect growth rate (30.00 ± 0.00), percent damaged wheat grains (10.44 ± 0.16%), percent grain weight loss (0.82 ± 0.06%) and weight of insect feeding residues (0.22 ± 0.02 g) were recorded on wheat grains stored in hermetic bag due to 100% mortality of T. castaneum in hermetic bag at 30 d. A significant and positive correlation between storage periods, insect growth rate, damaged wheat grains, grain weight loss and weight of insect feeding residues was observed, except for the storage bags which were significantly and negatively correlated with other factors. In addition, the simple and linear regressions analysis were significant (P < 0.01), and all the equations for these analyses were fitted for the regression models and perfectly described the association between the dependent and independent variables. Hermetic bag proved resistance to external environment fluctuations in abiotic factors such as temperature and relative humidity. While grain moisture in all other bags fluctuated with external environment. The results showed that quantitative and qualitative losses of stored wheat grains depends not only the type of storage bags, but also on the storage periods. T. castaneum can have a negative impact on wheat grains stored in all storage bags except hermetic bag. So, it is recommended that hermetic bag be used at farmers’ level to achieve greater benefits by reducing T. castaneum infestation.

Impact of heat stress on development and fertility of Drosophila suzukii Matsumura (Diptera: Drosophilidae)

Drosophila suzukii is a globally invasive fruit pest that costs millions in yield losses and increased pest management costs. Management practices for D. suzukii currently rely heavily on calendar-based applications of broad-spectrum insecticides, but decision-based applications are theoretically possible with refined population modeling and monitoring. Temperature conditions are strongly deterministic of insect growth rates, fecundity, fertility, and resulting population densities. Therefore, information about the effects of temperature can be incorporated into population modeling to accurately predict D. suzukii population densities in the field which is crucial to maximize pesticide application efficiency and improve sustainability. Here, we investigated the effects of chronic heat stress during all of juvenile development on egg-to-adult viability and fertility. We also investigated egg-to-adult viability under heat stress after heat shock of the maternal parent. We found that heat stress during development results in lower egg-to-adult viability, and reduced lifespan and fertility for surviving adults. However, heat-shock treatment of females prior to egg laying increased the egg-to-adult viability of their eggs under heat stress. Female flies that developed at 30 °C had smaller ovaries than the untreated group and male flies had less sperm in their testes, and no sperm in their seminal vesicles. We conclude that heat stress during development is likely to have negative effect on D. suzukii population dynamics in the field. However, the intensity of such negative impact will depend on the phenotypic state of their maternal parents.

Adverse effects of mosquito control using Bacillus thuringiensis var. israelensis: Reduced chironomid abundances in mesocosm, semi-field and field studies

The ecological consequences of mosquito control using the larvicide Bacillus thuringiensis israelensis (Bti) are still a matter of debate especially when it comes to adverse effects on non-target but susceptible non-biting midges (Chironomidae). Our work aimed to assess the effects of Bti applied in operational mosquito control rates on chironomid abundances in seasonal flooded freshwater wetlands. We assessed the invertebrate community alongside with aquatic insect emergence rates in studies with increasing ecotoxicological complexity, ranging from artificial mesocosms, over a semi-field approach using enclosures to natural conditions in field studies. Study sites represented different habitats (forest, meadow, floodplain) with regularly Bti treated and untreated temporal wetlands that are located in the Upper Rhine Valley, Germany. Larval chironomids were the most affected group of organism in the altered aquatic invertebrate communities of the Bti treated pond mesocosms. The larvae of the chironomid subfamilies Chironominae and Orthocladiinae were affected by Bti field concentrations while emergence rates of Tanypodinae did not change. The Bti treatment significantly reduced the targeted mosquitoes in the mesocosm and in the field studies. At the same time, however, the application of operational Bti field rates reduced overall chironomid emergence rates to about half of the control rates. The observed abundance reductions occurred independently of the ecological complexity in the study design in artificial mesocosms as well as realistic field conditions. The considerable reduction of the abundant non-target chironomids along with mosquitoes may subsequently lead to unwanted indirect negative effects for birds, bats and other aquatic organisms feeding on midges. Hence, large-scale applications of Bti for mosquito control in seasonal wetlands should be considered more carefully. This is of special importance when these wetlands are parts of national parks, nature reserves or Natura 2000 sites that were created for the protection of nature and environmental health.

Application of insulin signaling to predict insect growth rate in Maruca vitrata (Lepidoptera: Crambidae).

Insect growth is influenced by two major environmental factors: temperature and nutrient. These environmental factors are internally mediated by insulin/insulin-like growth factor signal (IIS) to coordinate tissue or organ growth. Maruca vitrata, a subtropical lepidopteran insect, migrates to different climate regions and feeds on various crops. The objective of this study was to determine molecular tools to predict growth rate of M. vitrata using IIS components. Four genes [insulin receptor (InR), Forkhead Box O (FOXO), Target of Rapamycin (TOR), and serine-threonine protein kinase (Akt)] were used to correlate their expression levels with larval growth rates under different environmental conditions. The functional association of IIS and larval growth was confirmed because RNA interference of these genes significantly decreased larval growth rate and pupal weight. Different rearing temperatures altered expression levels of these four IIS genes and changed their growth rate. Different nutrient conditions also significantly changed larval growth and altered expression levels of IIS components. Different local populations of M. vitrata exhibited significantly different larval growth rates under the same nutrient and temperature conditions along with different expression levels of IIS components. Under a constant temperature (25°C), larval growth rates showed significant correlations with IIS gene expression levels. Subsequent regression formulas of expression levels of four IIS components against larval growth rate were applied to predict growth patterns of M. vitrata larvae reared on different natural hosts and natural local populations reared on the same diet. All four formulas well predicted larval growth rates with some deviations. These results indicate that the IIS expression analysis explains the growth variation at the same temperature due to nutrient and genetic background.

Trophic ecology of adult male Odonata. I. Dietary niche metrics by foraging guild, species, body size, and location

1. Information on the dietary niches of adult odonates is sparse, as they are highly mobile and evasive animals, which makes them difficult to observe in their natural habitat. Moreover, there is a lack of knowledge on how varying behavioural traits of odonates relate to phenomena like niche partitioning.2. This study investigated niche partitioning amongst odonate species, foraging guilds and size classes in a riverine system in the Eastern Cape province of South Africa. A combination of stable isotope and fatty acid‐based niches was used to infer odonate feeding.3. Both fatty acid and stable isotope‐based niches showed that there was niche separation amongst odonates that forage in flight (fliers) and those that forage from a perch (perchers), amongst odonates of different size classes (damselflies, medium‐ and large‐sized dragonflies), and amongst species, although varying levels of niche overlap were observed in each case.4. Niche sizes of odonates varied between an upstream and a downstream site. Generally greater niche overlap was recorded at the narrow upstream site (associated with low insect emergence rates) than the wider downstream site (associated with high insect emergence rates), indicating that a greater degree of resource sharing occurred at the upstream site where aquatic food was less abundant.5. The findings of this study suggest that dietary niches of odonates can be influenced by foraging guild, body size, and/or environmental conditions, and additional study in a variety of regions is recommended to determine the greater applicability of these findings.

Trophic ecology of adult male Odonata. II. Dietary contributions of aquatic food sources

1. Insects that emerge from rivers provide nutritional subsidies to local riparian predators. Adult damselflies and dragonflies often benefit from aquatic resources, but their high mobility and evasiveness have made it difficult to monitor their diets.2. A dual fatty acid and stable isotope analysis approach was used to investigate the links between Odonata size and behaviour with proportions of their aquatically derived nutritional sources. Additionally, the study investigated the variation in dietary contributions of aquatic food sources to Odonata between two sections of a river, each with different aquatic productivity rates.3. Variations in body size and foraging method of Odonata in the Kowie River (South Africa) contributed to differences in the contributions of aquatic food sources to their diets. Large Odonata that consumed prey in flight had smaller proportions of aquatic indicator fatty acids and stable isotope‐generated proportions of aquatic food sources than did the smaller Odonata that consumed prey from perches.4. There was a considerable amount of interspecific variation in indicators of aquatic feeding, but Odonata at an upstream site had smaller proportions of aquatic indicators than those at a downstream site which had higher insect emergence rates.5. The findings of this study contribute information on the dynamics of feeding ecology among adult Odonata, and the substantial contributions of aquatic prey (&gt;80% of total diet in some cases) indicated that cross‐boundary trophic linkages via odonates are strong in the Kowie River.

Prospective evidence for independent nitrogen and phosphorus limitation of grasshopper (Chorthippus curtipennis) growth in a tallgrass prairie.

Insect herbivores play a pivotal role in regulating plant production and community composition, and their role in terrestrial ecosystems is partly determined by their feeding behavior and performance among plants of differing nutritional quality. Historically, nitrogen (N) has been considered the primary limiting nutrient of herbivorous insects, but N is only one of many potential nutrients important to insect performance. Of these nutrients, phosphorus (P) is perhaps the most important because somatic growth depends upon P-rich ribosomal RNA. Yet relatively few studies have assessed the strength of P-limitation for terrestrial insects and even fewer have simultaneously manipulated both N and P to assess the relative strengths of N- and P-limitation. Here, we tested for potential N and P limitation, as well as N:P co-limitation, on Chorthippis curtipennis (Orthoptera, Acrididae), an abundant member of arthropod communities of central US prairies. Our results demonstrate weak evidence for both N and P limitation of C. curtipennis growth rates in laboratory feeding assays. Importantly, P-limitation was just as strong as N-limitation, but we found no evidence for NP co-limitation in our study. Furthermore, nutrient limitation was not apparent in field studies, suggesting that insect growth rates may be predominately controlled by other factors, including temperature and predation. Our results suggest that P should be jointly considered, along with N, as a primary determinant of herbivore feeding behavior under both current and future climate conditions.

Changing global risk of invading greenbug Schizaphis graminum under climate change

The geographical range, abundance, growth rate, survival and mortality of insects are largely influenced by abiotic factors such as temperature and humidity. When suitable, these factors can positively influence the abundance of insect pests. It is in this light that the influence of climate change, particularly global warming, has direct bearing to crop protection. In this study, we simulated the potential distribution of the greenbug or wheat aphid Schizaphis graminum (Rondani) (Aphididae), a major global pest of wheat, using the climate matching tool CLIMEX (CLIMatic indEX) in global warming scenarios. To predict the potential distribution of the insect on CLIMEX at time periods 2030, 2070 and 2100, we utilize two global climate models (GCMs) at two emission scenarios. The result of CLIMEX modelling shows that the favourable climatic areas for S. graminum are subtropical to temperate at the current time. With global warming, under different scenarios current suitable and highly suitable areas in the northern hemisphere are expected to expand to higher latitudes by 2030 towards 2100; while areas in the southern hemisphere, where the pest’s living areas already have high temperature ranges, the occurrence of the pest will contract by 2030 since temperatures will exceed its heat limits. This study assists in predicting the potential risk areas that may be threatened by this pest in the future, providing supportive information for agricultural management practices and aid in the preparation of strategic plans to avoid possible economic damage posed by future expansion of the pest population due to climate change.

LIFE CYCLES AND SECONDARY PRODUCTION OF EPHEMEROPTERA, PLECOPTERA, AND TRICHOPTERA (INSECTA) UNDER AN EXTREME CONTINENTAL CLIMATE (RIVER KHARAA, MONGOLIA)

There are still knowledge gaps and uncertainties concerning the research of macroinvertebrates, in particular, a life cycle study of representative species are one such section of information missing in Mongolia. Therefore, this study was conducted within the framework of the biomonitoring program in the Kharaa River Basin under the research aims of the project entitled ‘Integrated Water Resources Management (IWRM) in Central Asia: Model Region Mongolia (MoMo)’. This study provided the first quantitative results on the life cycle, production, growth rate and emergence of aquatic insects from Mongolia, to allow comparisons with studies in other regions using the same methods. The 3-year study (2007-2009) of the life cycles of eighteen selected species according to the larval body size distribution and emergence period showed that the life cycle strategies in Ephemeroptera, Plecoptera, and Trichoptera and their production in the Kharaa River Basin clearly indicated adaptations to the harsh environmental conditions with strict univoltinism and low secondary production. In conclusion, it is essential to obtain knowledge especially about life cycle strategies of macroinvertebrates to predict re-colonisation potential of disturbed habitats and to evaluate the efficiency of management measures.

Physiological effects of compensatory growth during the larval stage of the ladybird, Cryptolaemus montrouzieri

The growth rate of insects may vary in response to shifty environments. They may achieve compensatory growth after a period of food restriction followed by ad libitum food, which may further affect the reproductive performance and lifespan of the resulting phenotypes. However, little is known about the physiological mechanisms associated with such growth acceleration in insects. The present study examined the metabolic rate, the antioxidant enzyme activity and the gene expression of adult Cryptolaemus montrouzieri (Coleoptera: Coccinellidae) after experiencing compensatory growth during its larval stages. Starved C. montrouzieri individuals achieved a similar developmental time and adult body mass as those supplied with ad libitum food during their entire larval stage, indicating that compensatory growth occurred as a result of the switch in larval food regime. Further, the compensatory growth was found to exert effects on the physiological functions of C. montrouzieri, in terms of its metabolic rates and enzyme activities. The adults undergoing compensatory growth were characterized by a higher metabolic rate, a lower activity of the antioxidant enzymes glutathione reductase, catalase, and superoxide dismutase and a lower gene expression of P450 and trehalase. Taken together, the results indicate that although compensatory growth following food restriction in early larval life prevents developmental delay and body mass loss, the resulting adults may encounter physiological challenges affecting their fitness.

Temperature-Mediated Development Thresholds of Sparganothis sulfureana (Lepidoptera: Tortricidae) in Cranberries

Larvae of Sparganothis sulfureana Clemens frequently attack cranberries, often resulting in economic damage to the crop. Because temperature dictates insect growth rate, development can be accurately estimated based on daily temperature measurements. To better predict S. sulfureana development across the growing season, we investigated the temperature range within which S. sulfureana larvae can feed and grow. Larvae were reared at 13 constant temperatures ranging from 6.5-38.6 °C. Larval growth rate was determined by the rate of change of larval weight across time. The respective growth rates among these temperatures were modeled using simple linear, cubic, and Lactin nonlinear development functions. These models isolated the lower temperature threshold at which growth became nonzero and the upper temperature at which growth was maximized. All three models were significantly predictive of S. sulfureana growth, but the cubic model best represented the observed growth rates, effectively isolating lower and upper thresholds of 9.97 and 29.89 °C, respectively. We propose that these thresholds be used to create a degree-day model of temperature-mediated S. sulfureana development.