Using scissors to quantify hardness of insects: do bats select for size or hardness?

Scissors are used to determine the hardness of fresh insects of different size and taxa. Our results indicate a strong relationship between the size of an insect and its hardness, which can be expressed as log( F _max)=0.65 × log( V )+ α . F _max is the maximal force needed to cut the insect and is our measure of insect hardness. V is the volume of the insect and α is a constant that can be derived for different insect taxa. The value of 0.65 was found as an average of beetle and moth samples, and this number appears consistent across insect taxa. We found that beetles averaged about 3.2 times harder than moths of the same size. Beetles were also more variable in hardness than moths, with the softest beetles about equal in hardness to an average moth of the same size. Using our data on insect hardness coupled with data on the diets of bats and their bite forces from the literature, we attempt to determine whether the upper size limit of insects taken by a bat is limited by the insect's dimensions or its hardness. Our results indicate that both these factors may be important.     

Inert dust insecticides: Part I. Mechanism of action

The mode of action of inert dust insecticides on the grain weevil ( Calandra granaria L.) has been investigated by determination of mortality-time curves and by a detailed study of the influence of dusts on the water relations of the insects. It has been found that dusts do not depend for their action on any chemical reactivity, some highly inert substances such as diamond and carborundum being very effective. A physical process is therefore indicated.
Dusts do not penetrate into the respiratory system, and although large amounts are ingested these seem to have little harmful effect.
It has been demonstrated that effective dusts increase the rate of evaporation of water from insects to the air, and that the relative killing powers of different dusts run parallel with their capacities for promoting evaporation. The results are in harmony with the view (proposed by earlier workers) that inert dusts kill insects by inducing death by desiccation.     

Inert dust insecticides: Part III. The effect of dusts on stored products pests other than Calandra granaria

The inert dusts used in Parts I and II against the grain weevil have been found effective in vitro against a variety of other insects infesting stored products, both larvae and adults. The order, as well as the magnitude, of effectiveness of a series of dusts differs for different species, but the mechanism of action appears to be the same, viz. promotion of evaporation of moisture, leading to death by desiccation. In contrast to the results with Calandra , highly adsorbent dusts like charcoal are much more effective on larvae than are mineral powders.
Dusts have a particularly striking action on the mealworm, and this case has therefore been investigated more fully. Dead mealworms when dusted do not lose water nearly as rapidly as live dusted ones.     

Auswirkungen von Diatomeenerde auf den Wasserhaushalt des Kornkäfers: Sitophilus granarius (L.) (Col., Curculionidae) und möglicher Einsatz innerhalb des Vorratsschutzes

Effects of diatomoceous earth on water content of Sitophilus granarius (L.) (Col., Curculionidae) and its possible use in stored product protection Increased problems caused by application of chemical pesticides within pest protection has led to the demand for non‐polluting, biologically specific active countermeasures. This study aimed to test the possible use of diatomaceous earth against Sitophilus granarius. It will also examine the physiological effects of amorphous diatomaceous earth against this insect. After 2 weeks, 100% mortality was observed of the adults treated with 2 g Fossil Shield^® per kilogram wheat, at 11–12% corn moisture content and relative humidity of about 62 ± 2%. The rise in grain moisture and relative humidity decreased the effectiveness of the Fossil Shield^®. It was observed, that the diatomaceous earth reduced the number of adult granary weevils and increased the mortality rate at development stages, but they did not completely prevent the hatching of the next generation. After contact with diatomaceous earth, the individuals of S. granarius had lost weight and reduced their water content, respectively. The adults significantly lost weight and body water after 1 day exposure to Fossil Shield^®. This showed that silica dusts break the water barrier of the cuticle. However, it increases the transpiration rate of water across the cuticle and several insects died through dehydration. At higher relative humidity diatomaceous earth was less effective toward S. granarius, because there was a lower permeability for water across the cuticle. This delays or rather prevents the drying action of diatomaceous earths. Furthermore, the addition of food affected the effectiveness of dusts against S. granarius. A lot of stored product beetles are able to produce metabolic water in the feed substrates. This ability protects them and works contrary to the loss of water.     

THE TOXICITY OF DDT IN ABRASIVE AND NON-ABRASIVE DUSTS TO THE RICE WEEVIL, CALANDRA ORYZAE L. (COLEOPT., CURCULIONIDAE)*

The toxicity of DDT in different dust carriers to the rice weevil, Calandra oryzae , was determined under standardized conditions, using deposits large enough to ensure that the insects accumulated an excess of dust.
Some evidence was obtained that DDT is transported to the cuticle as a vapour.
At high humidity, the toxicity of DDT was not markedly affected by any carrier except charcoal which reduced the toxicity, probably by absorption of DDT vapour. Small differences in toxicity of DDT caused by other carriers could not be accounted for by differences in their average particle size, bulk density, amount adhering to insect, surface area, abrasiveness to insects or effect on behaviour of the insect.
At low humidity, abrasive dusts killed the insects by desiccation, thus adding to the toxic effect of DDT. Abrasion of the insect's cuticle did not affect the apparent rate of penetration of DDT at 50% R. H. or at 95% R. H.
Starved insects were more susceptible to DDT poisoning, and in some experiments abrasive carriers increased the toxicity of DDT by preventing the insects from feeding.     

Group size affects the metabolic rate of a tropical beetle

ABSTRACT. . Dormancy is metabolically very costly for insects and other poikilotherms of the tropics because energy reserves are rapidly utilized at high temperature. Yet, the beetle Stenotarsus rotundus Arrow spends up to 10 months each year in a tropical lowland forest as a non-feeding adult, dependent upon its fat reserve as an energy source. While in this dormant state, the beetles aggregate in huge numbers and the size of the group greatly influences the metabolic rate. As group size increases, the metabolic rate decreases, and the minimum rate observed in the field (22 μ l O₂ g^-1 h^-1) is estimated to occur when group size reaches about 300 individuals. A decrease in metabolic rate can also be achieved by elevating relative humidity, thus suggesting that one function of the aggregation is to increase humidity within the group and thereby decrease metabolic rate.     

Pest control by the release of insects carrying a female-killing allele on multiple loci

With recent advances in genetics, many new strategies for pest control have become feasible. This is the second article in which we model new techniques for pest control based on the mass release of genetically modified insects. In this article we model the release of insects carrying a dominant and redundant female killing or sterilizing (FK) allele on multiple genetic loci. If such insects are released into a target population, the FK allele can become widely spread in the population through the males while reducing the population each generation by killing females. We allow the number of loci used to vary from 1 to 20. We also allow the FK allele to carry a fitness cost in males due to the gene insertions. Using a model, we explore the effectiveness and optimal strategies for such releases. In the most ideal circumstances (no density-dependence and released insects equal in fitness to wild ones), FK releases are several orders of magnitude more effective than equal sized sterile male releases. For example, a single release of 19 FK-bearing males for every two wild males, with the released males carrying the FK allele on 10 loci, reduces the target population to 0.002% of no-release size. An equal sized sterile release reduces the target population to 5% of no-release size. We also show how the effectiveness of the technique decreases as the fitness cost of the FK alleles in males increases. For example, the above mentioned release reduces the target population to 0.7% of no-release size if each FK allele carries a fitness cost in males of 5%. Adding a simple model for density-dependence and assuming that each of the released males carries the FK allele on six loci, we show that the release size necessary to reduce the target population to 1/100 of no-release size in 10 generations of releases varies from 0.44:1 to 4:1 (depending on parameter values). We also calculate the optimal number of loci on which to put the FK allele under various circumstances.     

THE CONTROL OF BLOWFLIES INFESTING SLAUGHTER-HOUSES

A field experiment has been conducted to control blowflies which fell as mature larvae from railway wagons carrying domestic refuse and infested the soil at the sidings of a refuse collecting and sorting depot.
The surface of the soil was treated so that the insects were exposed to insecticide both as migrating larvae and newly emerged adults. Dusts and emulsions of DDT and BHC were compared on the basis of equal cost. A method was evolved for obtaining quantitative measurements of the effectiveness of the treatments by trapping flies emerging from the soil.
DDT was more effective than BHC, dusts were more effective than emulsions, and small quantities applied twice weekly were more effective than a correspondingly heavy dose applied monthly. DDT dust applied twice weekly was estimated to have killed 79.7% of larvae and pupae and 95.7% of emerging adults: overall control was 99.1%. Equally high control was maintained when the method was adopted as a routine measure by the local authority.     

Chemometric evaluation of pharmaceutical properties of antipyrine granules by near-infrared spectroscopy

The purpose of this research was to apply near-infrared (NIR) spectroscopy with chemometrics to predict the change of pharmaceutical properties of antipyrine granules during granulation by regulation of the amount of water added. The various kinds of granules (mean particle size, 70–750 μm) were obtained from the powder mixture (1 g of antipyrine, 6 g of hydroxypropylcellulose, 140 g of lactose, and 60 g of potato starch) by regulation of the added water amount (11–19 wt/wt%) in a high-speed mixer. The granules were characterized by mean particle size, angle of repose, compressibility, tablet porosity, and tablet hardness as parameters of pharmaceutical properties. To predict the pharmaceutical properties, NIR spectra of the granules were measured and analyzed by principal component regression, (PCR) analysis. The mean particle size of the granules increased from 81 μm to 650 μm with an increase in the amount of water, and it was possible to make larger spherical granules with narrow particle size distribution using a high-speed mixer. Angle of repose, compressibility, and porosity of the tablets decreased with an increase of added water, but tablet hardness increased. The independent calibration models to evaluate particle size, angle of repose, and tablet porosity and hardness were established by using PCR based on NIR spectra of granules, respectively. The correlation coefficient constants of calibration curves for prediction of mean particle size, angle of repose, tablet porosity, and tablet hardness were 0.9109, 0.8912, 0.7437, and 0.8064, respectively. It is possible that the pharmaceutical properties of the granule, such as mean particle size, angle of repose, tablet porosity, and tablet hardness, could be predicted by an NIR-chemometric method.     

Chemical constituents and fumigant toxicity of essential oil from Carum copticum against two stored product beetles

Plant secondary metabolites play an important role in plant-insect interactions and therefore such compounds may have insecticidal or antifeedant activity against insects. Carum copticum C. B. Clarke （Apiaceae） is one of these plants that have medicinal effects on humans. The chemical composition of the essential oil from dry seeds of C. copticum was studied by gas chromatography （GC） and gas chromatography mass spectrometry （GC-MS）. Thymol （41.34%）,α-terpinolene （17.46%） and ρ-cymene （11.76%） were found to be the major constituents of the oil. In fumigant toxicity tests with the essential oil against adults of Sitophilus oryzae （L.） and Tribolium castaneum （Herbst） at 27 ±1℃ and 60% ± 5% RH, it was observed that S. oryzae （LC50 = 0.91 μL/L） were significantly susceptible than T. castaneum （LC50 = 33.14 μL/L）. The mortalities of the insect species reached 100% at concentrations higher than 185.2 μL/L and 12-h exposure time. The findings indicate the strong insecticidal activity of C. copticum oil and its potential role as a fumigant for storedproduct insects.     

A MICRO-DROP APPLICATOR AND ITS USE FOR THE TREATMENT OF CERTAIN SMALL INSECTS WITH LIQUID INSECTICIDE

An instrument has been constructed for applying minute drops of liquid insecticide to selected parts of individual insects. The principle of the instrument, which is not original, is to express minute amounts of liquid from a hypodermic syringe, and blow the drop from the needle tip by a puff of air. This model is considered to have advantages over previous models working on the same principle. In particular, a very convenient form of fitting was developed for blowing the drop from the needle tip, and fittings of this type could be incorporated in existing similar applicators with little modification of the latter. The high directional accuracy of dropfire necessary for treating selected parts of small insects was achieved.
An immersion method was developed for determining the sizes of individual drops of Shell oil P₃₁ delivered, and hence the uncontrolled variability of drop-volume. It showed that the standard deviation in the volumes of drops intended to be equal in size was about 9% of a mean volume of 0.017 μ1. falling progressively to about 2% as the mean volume increased to 0.33 μl. These standard deviations, however, are of limited value, because the sizes of successive drops delivered appeared frequently to be correlated. A method in which the drops are delivered on to an oleophobic surface for measurement of the diameters of the oil lenses formed was found insufficiently accurate for determining the relative variability of drops of P_31.
A suction method was devised for manipulating, without anaesthetization or chilling, small beetles such as Calandra and Tribolium. This enabled large numbers to be individually treated with the applicator in a reasonable time. A similar but slower method was used successfully with the larvae of Ephestia. The biological results achieved have been very satisfactory.
The effects of uncontrolled variation in drop size on dose-response data are discussed.     

Marking Triatoma brasiliensis,Triatoma pseudomaculata and Rhodnius nasutus Nymphs with Trace Elements: Element Persistence and Effects of Marking on Insect Mortality

BackgroundField ecologists often rely on mark-release-recapture (MRR) experiments to estimate population dynamics parameters for a given species. In the case of a medically important taxon, i.e., a disease vector, inferences on species survival and dispersal rates are particularly important as they have the potential to provide insights into disease transmission dynamics in endemic areas. Medical entomologists have traditionally used fluorescent dusts to externally mark the cuticle of insects. However, dust marking is usually restricted to the adult life stage because immature insects lose the mark when they molt.Conclusions/SignificancePrevious evidence shows that there is little or no genetic differentiation between populations at the microgeographic level, which often precludes indirect estimations of dispersal capability based on genetic markers. In such situations, MRR studies are more suitable as they measure insect movement directly from one site to another, instead of effective migration (i.e. gene flow). The determination of a reliable and persistent marking method is the first step towards the development of meaningful ecological estimates through the application of MRR methodology. Here, we have identified trace elements that can be used for mark and recapture studies of three triatomine species in Brazil.     

Responses in metabolic rate to changes in temperature in diapausing Colorado potato beetle Leptinotarsa decemlineata from three European populations

Many insects survive adverse periods in seasonal environments by entering diapause, a deep resting stage, during which energy consumption is typically low and gas exchange is in the form of a discontinuous gas exchange cycle (DGC). Because insects in high‐latitude environments are severely time constrained during summer, an effective diapause termination with careful regulation of metabolic rate is important. The present study examines whether diapausing Colorado potato beetles Leptinotarsa decemlineata Say originating from three latitudinally different regions in Europe differ in their quantitative or qualitative gas exchange patterns in response to an increasing temperature. Overall production of gaseous CO₂, as well as qualitative patterns relating to the DGC, are measured at a late stage of diapause at four different temperatures in increasing order from 13, 18, 23 to 28 °C. Overall CO₂ production is found to be lower in the two northern populations (61°49′N and 55°75′N) compared with the southernmost population (45°48′N) but increases as a function of temperature in all populations in a similar way. However, in the northern populations, raising the temperature increases the amount of CO₂ discharged during single DGC peaks, whereas the DGC frequency remains relatively unchanged. By contrast, in the southernmost population, the amount of CO₂ discharged during individual DGC peaks remains relatively unchanged, whereas the DGC frequency increases as a function of temperature. The observed differences may relate to water retention benefits or, alternatively, energetic benefits relating to heightened gas exchange efficiency in hypoxic or hypercapnic environments. Overall, the results suggest that, although populations of L. decemlineata may have similar thermal sensitivities, they have different qualitative strategies to regulate metabolic re‐activation at diapause termination.     

Unpredictable environments,nuptial gifts and the evolution of sexual size dimorphism in insects: an experiment

Many insects have a mating system where males transfer nutrients to females at mating, which are often referred to as ''nuptial gifts''. Among butterflies, some of the characteristic features of these species are polyandry (females mate multiple times), and relatively large male ejaculates. When males produce part of the resources used for offspring, the value of body size might then increase for males and decrease for females. The male/female size ratio is also observed to increase when the degree of polyandry and gift size increase. Butterfly species where gift-giving occurs are generally more variable in body size, suggesting that food quality/quantity fluctuates during juvenile stages. This will cause some males to have much to provide and some females to be in great need, and could be conducive to the evolution of a gift-giving mating system. In such a system, growing male and female juveniles should react differently to food shortage. Females should react by maturing at a smaller size since their own lack of reproductive resources can partly be compensated for by male contributions. Males have to pay the full cost of decreased reproduction if they mature at a small size, making it more important for males to keep on growing, even when growth is costly. An earlier experiment with the polyandrous and gift-giving butterfly, Pieris napi, supported this prediction. The pattern is expected to be absent or reversed for species with small nuptial gifts, where females do not benefit from mating repeatedly, and will thus be dependent on acquiring resources for reproduction on their own. To test this prediction, we report here on an experiment with the speckled wood butterfly, Pararge aegeria. We find that growth response correlates with mating system in the two above species, and we conclude that differences in environmental conditions between species may act as an important factor in the evolution of the mating system and sexual size dimorphism.     

Can endopolyploidy explain body size variation within and between castes in ants?

Endoreduplication is the process by which the nuclear genome is repeatedly replicated without mitotic cell division, resulting in nuclei that contain numerous additional genome copies. Endoreduplication occurs widely throughout Eucarya and is particularly common in angiosperms and insects. Although endoreduplication is an important process in the terminal differentiation of some specialized cell types, and often increases cell size and metabolism, the direct effects of increasing nuclear ploidy on cell function are not well resolved. Here, we examine if endoreduplication may play a role in body size and/or caste differentiation in ants. Nuclear ploidy was measured by flow cytometry of whole individuals (providing the basis for overall body size patterns) and individual body segments for multiple polymorphic ant species. We used cell cycle values, interpreted as the mean number of endocycles performed by each cell in the sample, as our measure of overall endoreduplication. Among females of four polymorphic ant species, endoreduplication was positively related with size within the worker caste, but was not related to caste generally in two species where we also examined queens. Additionally, abdomens had the greatest endoreduplication of all body parts regardless of caste or size. We also found that males, having derived from haploid unfertilized eggs, had the highest rates of endoreduplication and may compensate for their haploid origin by performing an additional endocycle relative to females. These results suggest that endoreduplication may play a role in body size variation in eusocial insects and the development of some segment‐specific tissues.     

Population genomics of eusocial insects: the costs of a vertebrate‐like effective population size

The evolution of reproductive division of labour and social life in social insects has lead to the emergence of several life‐history traits and adaptations typical of larger organisms: social insect colonies can reach masses of several kilograms, they start reproducing only when they are several years old, and can live for decades. These features and the monopolization of reproduction by only one or few individuals in a colony should affect molecular evolution by reducing the effective population size. We tested this prediction by analysing genome‐wide patterns of coding sequence polymorphism and divergence in eusocial vs. noneusocial insects based on newly generated RNA‐seq data. We report very low amounts of genetic polymorphism and an elevated ratio of nonsynonymous to synonymous changes – a marker of the effective population size – in four distinct species of eusocial insects, which were more similar to vertebrates than to solitary insects regarding molecular evolutionary processes. Moreover, the ratio of nonsynonymous to synonymous substitutions was positively correlated with the level of social complexity across ant species. These results are fully consistent with the hypothesis of a reduced effective population size and an increased genetic load in eusocial insects, indicating that the evolution of social life has important consequences at both the genomic and population levels.     

Cumulative effects of volcanic ash on the food preferences of two Orthopteran species

Inert dusts are an early form of insecticide which is still in use. One of the most common inert dusts is volcanic ash. In order to study the reaction of rangeland grasshoppers, Dichroplus vittigerum (Acrididae) and a katydid, Burgilis mendosensis (Phaneropteridae), to the presence of volcanic ash in their food sources and how this reaction changed as a function of time, we conducted paired preference tests between clean leaves of their preferred host plant and leaves exposed to volcanic ash of different grain size. The behavioral response was measured as the rating on the Thurstonian preference scale of leaves with ash in relation to clean leaves. The results showed that the avoidance of volcanic ash increased as a function of time in both species. Both species studied are occasionally exposed to volcanic activity, and come from an area in which a volcanic eruption had recently occurred. As their populations did not decrease after the ash fall, we propose that some behavioral responses such as avoidance of places with ash, works as tolerance mechanism to inert dusts exposure.     

Size of prey ingested by whitefish,Coregonus sp., larvae. Are Coregonus larvae gape-limited predators?

The feeding ecology of whitefish, Coregonus , larvae in oligotrophic Lake Sarnen and eutrophic Lake Hallwil is presented, taking into consideration the size of the prey ingested in relation to the mouth size of larvae and to the availability of zooplankton.
When larvae grow from 10 to 16 mm their mouth width increases from 500 to 1000 μm while their gape height, with the mouth open at 45 and 90°, increases from 200 to 400 μm and from 400 to 700 μm, respectively, whichever lake is considered.
The differences found in the mean prey width between the two lakes arise in part from the composition of diets, and in part from differences in size of the available prey organisms. Whatever the origin of the larvae and the taxon we consider, larvae seem to ingest the most abundant prey size without selecting the biggest ones available even if, from a mechanical point of view, they would be able to ingest them.
Taking into account the generally low density of zooplankton in the uppermost layer of the lake, we conclude that whitefish larvae eat in the manner such as to decrease the cost of prey capture, in terms of energy and time, by choosing the more abundant prey available.     

叶面分离苏云金芽孢杆菌的研究进展

苏云金芽孢杆菌是一种在芽孢形成的同时能形成杀虫晶体蛋白的细菌,广泛存在于土壤、昆虫、贮藏物、仓库尘埃、植被等昆虫接触物上.植物叶片作为Bt分离的重要来源,目前对这方面的研究相对较少,国内刚刚起步.本文就叶面分离Bt的研究成果、叶片采样及分离方法进行阐述.     

双翅目昆虫传粉研究进展

昆虫传粉不仅在自然生态系统中发挥着十分重要的作用,也和农业生态系统中产量密切相关。众所周知,膜翅目昆虫是最重要的传粉昆虫。双翅目昆虫分布广,物种多,数量大,也是一类十分重要的传粉昆虫,但其传粉作用未受到足够的重视。本文主要综述了双翅目传粉昆虫的主要种类、传粉效力、传粉特征、与植物的协同进化以及双翅目昆虫传粉的生态学意义。据记载双翅目昆虫中至少有71个科涉及虫媒种类,目前有资料显示访花昆虫类群中双翅目约有54 417种,按涉及的种数排序居于昆虫纲传粉昆虫目中第4位。尽管双翅目昆虫单次访问可携带花粉量相对较少(相比于膜翅目),但是较高访问速率及庞大的个体数量,保证了其作为有效传粉者的地位。传粉综合征能够有效揭示植物与传粉者的协同进化关系,尤其是对一些专化传粉现象(如五味子科-瘿蚊系统)和泛化传粉的深入研究,更加深了我们对协同进化的理解。就生态学意义而言,一方面双翅目传粉昆虫是膜翅目传粉昆虫的有益补充,另一方面在一些特殊环境中,双翅目昆虫具有不可替代的作用。当前传粉昆虫(包括双翅目)数量急剧下降,而且双翅目昆虫的传粉价值还利用较少。结合我国当前的研究现状提出了以下未来研究重点:1)加深双翅目传粉效力和适应意义的案例研究以明确双翅目昆虫在传粉体系中的地位;2)加强栖息地格局变化与昆虫多样性的研究以明确栖息地改变对昆虫的影响程度;3)梳理访花和传粉、专化传粉和泛化传粉等关系以更加明确双翅目昆虫在与植物协同进化中的作用;4)逐步深入探讨花粉浪费和花粉竞争以探究传粉策略和植物繁殖策略。这些努力将为双翅目传粉昆虫的知识普及、资源保护与利用研究等方面提供参考。