THE EFFECT OF REPEATED SPRAYING OF INSECTS IN INCREASING THEIR RESISTANCE TO INSECTICIDES

During the selection of a stock of Drosophila melanogaster for resistance to DDT, in which carbon dioxide was used for purposes of anaesthesis, a sensitivity to this gas developed. The phenomena closely paralleled those shown by the CO₂-sensitive ebony stock isolated by L'Héritier and his co-workers. An experimental analysis of its effect upon DDT sensitivity was made. It was found that a stock selected for CO₂ resistance gave the same probit regression line as the original stock. A CO₂-sensitive stock, whether anaesthetized with nitrogen or carbon dioxide, gave the same regression line at a temperature of 25° C. at which CO₂ sensitivity disappeared, or at 15° C. if adjustment to the proportion of deaths in the control was made. The effect of CO₂ was therefore to limit the population from which selection is made for DDT resistance, rather than to alter the distribution of DDT resistance within the stock.     

THE EFFECT OF REPEATED SPRAYING OF INSECTS ON THEIR RESISTANCE TO INSECTICIDES

The administration of carbon dioxide in sublethal concentrations or for sublethal periods of time gave rise to an increased resistance to its effect in a strain of Drosophila melanogaster susceptible to the toxic effects of this gas. The effect did not appear to be permanent.
The successive administration by spraying of sublethal concentrations of DDT and BHC did not increase the resistance of a strain of D. melunoguster to their effects, either in the insects sprayed or their progeny. Only when the dosages were such as to give a high death-rate did a significant increase of resistance of the progeny of the treated insects take place; the tendency was if anything to increase susceptibility, although the indications were not in favour of DDT acting as acumulative poison.
In a preliminan series of tests the topical application of D D T in sublethal doses to the adult insects resulted in a reduction in the amount or in the rate of egg laying.     

THE EVOLUTION OF RESISTANCE TO HERBIVORY IN IPOMOEA PURPUREA. I. ATTEMPTS TO DETECT SELECTION

In this study, we looked for evidence of directional or stabilizing/disruptive selection on plant size and on the level of damage (resistance) caused by four types of herbivores in the annual morning glory Ipomoea purpurea. Selection was estimated by standard phenotypic regression analysis and by regression on breeding values. The phenotypic regression analysis revealed directional selection for all five characters (i.e., plant size and resistance to four types of herbivores) and indicated that plant size and resistance to corn-earworm damage were subject to stabilizing selection. By contrast, the analysis using breeding values revealed directional selection only for plant size and resistance to corn earworms, while none of the characters examined indicated stabilizing or disruptive selection. These results suggest that intermediate levels of damage in I. purpurea are, in general, not maintained by stabilizing selection. Rather, they may reflect either 1) a transient state that exists while directional selection pushes the population toward complete resistance (or, in one case, total absence of resistance) or 2) the evolution of susceptibility to damage by genetic drift.     

EVOLUTIONARY ECOLOGY OF DATURA STRAMONIUM L. IN CENTRAL MEXICO: NATURAL SELECTION FOR RESISTANCE TO HERBIVOROUS INSECTS

It has been assumed that herbivores constitute a selective agent for the evolution of plant resistance. However, few studies have tested this hypothesis. In this study, we look at the annual weed Datura stramonium for evidence of current natural selection for resistance to herbivorous insects. Paternal half-sib families obtained through controlled crosses were exposed to herbivores under natural conditions. The plants were damaged by two folivorous insects: the tobacco flea beetle Epitrix parvula and the grasshopper Sphenarium purpurascens. Selection was estimated using a multiple-regression analysis of plant size and of damage by the two herbivores on plant fitness measured as fruit production for both individual phenotypes and family breeding values (genetic analysis). Directional phenotypic selection was detected for both larger plant size and lower resistance to the flea beetles, whereas stabilizing phenotypic selection was revealed for resistance to S. purpurascens. However, performing the same analyses on the breeding values of the characters revealed directional and stabilizing selection only for plant size. Thus, no agreement existed between the results of the two types of analyses, nor was there any detectable potential for genetic change in the studied population because of selection on herbivore resistance. The narrow-sense heritability of every trait studied was small (all <0.1) and not different from zero. The potential for evolutionary response to natural selection for higher resistance to herbivores in the studied population of D. stramonium is probably limited by lack of genetic variation. Natural selection acts on phenotypes, and the detection of phenotypic selection on resistance to herbivores confirms their ecological importance in determining plant fitness. However, evolutionary inferences based solely on phenotypic selection analyses must be interpreted with caution.     

云南省致乏库蚊对四种杀虫剂的敏感性调查

云南省分别在１９７８—１９８１ 年和１９９２—１９９４ 年间开展了致乏库蚊对杀虫剂的敏感性调查。根据剂量死亡率回归线和区分剂量线相交点所处的位置, 判定１９７８ —１９８１ 年的抗性等级（ＬＣ５０ 测定） , 再与同一监测点１９９２—１９９４ 年抗性级（区分剂量法） 比较, 评估其敏感性。结果云南大部份地区致乏库蚊对ＤＤＴ、杀螟硫磷和敌百虫, 由敏感（Ｓ） 或初步抗性（Ｍ） 发展为初步抗性或抗性（Ｒ）, 原来的Ｒ种群仍保持不变; 但对马拉硫磷仍象１０ 多年前一样敏感。     

THE EVOLUTION OF RESISTANCE TO HERBIVORY IN IPOMOEA PURPUREA. II. NATURAL SELECTION BY INSECTS AND COSTS OF RESISTANCE

An important component of the process of coevolution between plants and their insect herbivores is the imposition of selection on plants by insects. Although such selection has been inferred from indirect evidence, little direct evidence for it exists. One goal of this study was to seek direct evidence by determining, for a single plant-herbivore system, whether insect herbivores impose selection on their host plants. A second goal was to determine whether costs are associated with genotypes that confer resistance to herbivores, as has been commonly postulated. The annual morning glory, Ipomoea purpurea, exhibits genetic variation in resistance to four different types of insects. For three of these types, most of the genetic variation is additive. Removal of insect herbivores increased the number of seeds produced by I. purpurea by 20% and eliminated additive genetic variation for seed number (fitness). This result implies that herbivores impose selection on some trait(s) of their host plants. Coupled with selection for decreased damage by corn earworms, as revealed by a negative additive genetic covariance between damage and fitness, this result suggests that insect herbivores impose selection on resistance to corn earworms in I. purpurea. Two types of cost of resistance to herbivores were sought in I. purpurea: 1) internal trade-offs in allocation of resources and 2) ecological trade-offs between resistances to different insects. No costs of either type were detected. This result suggests that cost-benefit arguments that attempt to predict the evolution of levels of resistance to herbivores are not applicable to I. purpurea.     

神经递质释放与家蝇对拟除虫菊酯抗性关系研究

通过生物测定比较溴氰菊酯、氯菊酯和DDT对Dec-R,2C1-R,DDT-R和敏感(SP)家蝇Musca domestica vicina的毒力,表明三个抗性品系对溴氰菊酯、氯菊酯和DDT均有很高的抗性,抗性倍数分别达120 912,6 032和112.2倍,并对上述三种杀虫剂有明显的交互抗性和抗击倒效应。杂交试验表明Dec-R对溴氰菊酯的抗性是一个隐性基因,电生理试验表明抗性家蝇中枢神经系统(CNS)对药剂敏感度的降低是其产生抗性和交互抗性的重要机制。研究结果表明Dec-R和2CLR家蝇品系中存在有击倒抗性因子(Kdr)。当用1×10^-7mol/L溴氰菊酯对SP家蝇脑突触体在提高K+浓度去极化后,可加强3H-胆碱的释放,而在Dec-R品系中,溴氰菊酯浓度提高到1×10^-4m0l/L也未能加强³H-胆碱的释放,表明溴氰菊酯与神经递质的释放和钠通道亲和性的降低是抗性的主要机制。     

LATITUDINAL CLINE IN DROSOPHILA MELANOGASTER FOR KNOCKDOWN RESISTANCE TO ETHANOL FUMES AND FOR RATES OF RESPONSE TO SELECTION FOR FURTHER RESISTANCE

We have introduced a device for selecting Drosophila for increased resistance to very high concentrations of ethanol fumes. This device has enabled us to: 1) select quickly and easily over a thousand flies at a time, and 2) score the knockdown time of every fly in the distribution, while causing very little injury to the flies. A sample of nine west coast populations of Drosophila melanogaster showed a significant trend toward higher knockdown resistance in more northern populations. A population's level of knockdown resistance was virtually uncorrelated with its alcohol dehydrogenase (Adh) allele frequencies. Five of the above nine populations were then subjected to selection for further knockdown resistance. Each population was divided randomly into four groups of 256 flies: two lines to be selected, and two lines to remain unselected as control lines. In every generation each selected line was measured for knockdown resistance, and the last quartile of flies to be knocked down was saved to continue the selection cycle. Population sizes of the selected and unselected lines were all maintained at 256. Realized heritability, based on the responses to selection of the first four generations, was calculated for each selected line. The five populations were significantly heterogeneous for heritability estimates; the average heritability of the five populations pooled was 0.143 ± 0.019. Over the course of twelve generations, the ten selected lines increased their knockdown times by an average factor of 2.40. Before selection, the five populations were heterogeneous for knockdown resistance, and resistance was greatest among the most northern populations. The amount of change of knockdown resistance over the course of selection was also correlated with latitude: the most southern population increased its knockdown time by a factor of 2.23, and the most northern population increased it by a factor of 2.55. After ten generations of selection, the cline of knockdown resistance was about 4.5 times as steep as that before selection. Small phenotypic differences among populations before selection were thus exaggerated by the action of selection. The differences among populations in their rates of response to selection were attributed to genetic differences that existed before selection. The pattern of change of Adh frequencies over the course of selection was very inconsistent, both among and within populations. From this inconsistency of change of Adh alleles with selection, and the lack of correlation between Adh frequencies and knockdown resistance before selection, we concluded that Adh frequency changes could not have had much effect on the responses of the selected lines.     

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.     

植物的诱导抗虫性

植物对植食性昆虫的抗性可包括两个方面,即植物的组成抗性（constitutiveresistance）和诱导抗性（inducedresistance）。组成抗性是指植物在遭受植食性昆虫进攻前就已存在的抗虫特性;而诱导抗性是指植物在遭受植食性昆虫进攻后所表现出来的一种抗虫特性[1,2]。根据作用世代的不同,诱导抗性又分为迅速的诱导抗性（rapidlyinducedre－sistance,RIR）和滞后的诱导抗性（delayedinducedresistance,DIR）。前者是指对当前世代的植食性昆虫的影响,而后者是指对后续的1～几个世代的植食性昆虫的影响[2]。研究植物的诱导抗虫性,不仅能在…     

COSTS OF COUNTERDEFENSES TO HOST RESISTANCE IN A PARASITOID OF DROSOPHILA

Abstract The ability of a parasitoid to evolve enhanced counterdefenses against host resistance and its possible costs were studied in a Drosophila -parasitoid system. We reared Asobara tabida (Braconidae, Hymenoptera) exclusively on D. melanogaster to impose artificial selection for improved counterdefenses against cellular encapsulation, the main host defense against parasitism. Controls were reared on D. subobscura , the main host of the population of wasps from which the laboratory culture was derived and a species that never encapsulates parasitoids. We observed improved survival and avoidance of encapsulation in all five selection lines compared to their paired control lines, although there was unexpected variation among pairs. Improved survival was associated with parasitoid eggs becoming embedded in host tissue, where they were protected from circulating haemocytes. There were no differences among lines in average adult size, fat content, egg load, or performance on D. subobscura . However, the duration of the egg stage in selection lines was longer than that of control lines, probably because of reduced nutrient and/or oxygen supply when eggs are embedded in host tissue. We suggest that this delay in hatching reduces the probability of parasitoid survival if another parasitoid egg is laid in the same host (superparasitism or multiparasitism) and hence is a cost of enhanced counterdefenses against host resistance.     

GENETICS OF HORIZONTAL RESISTANCE TO DISEASES OF CROPS

(1) Horizontal resistance (HR) to diseases of crops has the following leading features: it is polygenically controlled and must be studied by biometrical-genetic methods; it is pathotype-non-specific and essentially ‘durable’; it has several components (e.g. infection rate, latency period, sporulation potential) which tend to be correlated; its use is relevant to the control of all classes of pathogen (fungi, bacteria, viruses, insects, nematodes); though often unrecognized, it is very common and generally the means by which ‘minor’ diseases remain minor. HR may be contrasted with ‘vertical resistance’ (VR) which is procured by major genes and is pathotype-specific. VR has uses in particular circumstances but has often failed against airborne epidemic pathogens such as many rusts; hence the importance of understanding HR. (2) In this review the genetic evidence of HR is reviewed and examples are summarized in appendices. Very diverse crops, places and pathogens are represented. So far as may be judged, HR is indeed universal, and found or constructable wherever sought. The most important genetic evidence is based on generation mean and variance analysis, general and specific combining ability, offspring-parent regression and response to selection. Useful supplementary evidence comes from historical observations, continuity and repeatability of resistance and yield-related effects. (3) The main conclusions are that HR is universally available, usually highly heritable and responsive to selection, already keeps a host of crop diseases down to acceptably low levels and has socio-economically attractive features that are likely to increase its use in the future. In particular, it offers long-term stability of performance that must be valuable to small farmers in the Third World and is environmentally attractive because successful breeding programmes minimize the need for environmentally damaging chemical protectants. ‘Green’ pressures are likely to favour HR and some relevance to public policy is thereby implied.     

RATES OF FLORAL EVOLUTION: ADAPTATION TO BUMBLEBEE POLLINATION IN AN ALPINE WILDFLOWER,POLEMONIUM VISCOSUM

Animal pollinators are thought to shape floral evolution, yet the tempo of this process has seldom been measured. I used the prediction equation of quantitative genetics, R = h²S , to predict the rate at which a change in pollinator abundance may have caused divergence in floral morphology of the alpine skypilot, Polemonium viscosum. A selection experiment determined the rate at which such divergence can actually proceed. Corolla flare in this species increases by 12% from populations pollinated by a wide assemblage of insect visitors to those pollinated only by bumblebees. To simulate the evolutionary process giving rise to this change, I used a pollinator selection experiment. Plants with broad flowers set significantly more seeds than plants with narrow flowers under bumblebee pollination but had equivalent fecundity when visited by other insects or hand-pollinated. Bumblebee-mediated selection for broad corolla flare intensified from 0.07 at seed set to 0.17 at progeny establishment. Maternal parent-offspring regression yielded a confidence interval of 0.22–1.00 for trait heritability. Given these parameter estimates, the prediction equation shows that broadly flared flowers of bumblebee-pollinated P. viscosum could have evolved from narrower ones in a single generation. This prediction is matched by an observed 9% increase in offspring corolla flare after a single bout of bumblebee-mediated selection, relative to offspring of unselected controls. Findings show that plant populations can adapt rapidly to abrupt changes in pollinator assemblages.     

昆虫抗药性靶标不敏感机制的研究进展

靶标不敏感（targetsiteinsensitivity）是昆虫对杀虫剂产生抗药性的一个极为重要的生化机制,已在多种昆虫对多种杀虫剂的抗性中发现[1,2],最著名的便是：变构乙酰胆碱酯酶（alteredacetvlcholinesterase,简称变构AChE）对有机磷和氨基甲酸酯类杀虫剂的抗性、不敏感的Na 通道（insensitivesodiumchannel）对DDT和除虫菊酯的击倒抗性（knockdownresistance,kdr）,以及不敏感的γ-氨基丁酸受体（insensitiveGABAreceptor）对环戊二烯类杀虫剂和γ-六六六的抗性[3]。80年代以来,众多学者利用各种技术尤其是分子生物学技术对上述靶…     

Effect of selection for dichlorodiphenyltrichloroethane (DDT) resistance on the uptake and breakdown of DDT in Aedes aegypti L

Aedes aegypti larvae and adults were selected to high levels of resistance with dichlorodiphenyltrichloroethane (DDT) along separate lines. The larval-selected line showed three responses associated with larval resistance: increased detoxication of DDT by dehydrochlorination to dichlorodiphenyldichloroethane DDE (demonstrated both in vivo and in vitro), increased tolerance to unmetabolised ("residual") DDT and, a reduction in uptake of DDT. Larval selection caused very little change in adult resistance or the uptake of DDT by adults, but there was an increase in dehydrochlorination. In the adult-selected line dehydrochlorination was increased by selection and was significantly correlated with resistance.     

ECOLOGICAL COSTS OF PLANT RESISTANCE TO HERBIVORES IN THE CURRENCY OF POLLINATION

In this paper, we examine how ecological costs of resistance might be manifested through plant relationships with pollinators. If defensive compounds are incorporated into floral structures or if they are sufficiently costly that fewer rewards are offered to pollinators, pollinators may discriminate against more defended plants. Here we consider whether directional selection for increased resistance to herbivores could be constrained by opposing selection through pollinator discrimination against more defended plants. We used artificial selection to create two populations of Brassica rapa plants that had high and low myrosinase concentrations and, consequently, high and low resistance to flea beetle herbivores. We measured changes in floral characters of plants in both damaged and undamaged states from these populations with different resistances to flea beetle attack. We also measured pollinator visitation to plants, including numbers of pollinators and measures of visit quality (numbers of flowers visited and time spent per flower). Damage from herbivores resulted in reduced petal size, as did selection for high resistance to herbivores later in the plant lifetime. In addition, floral display (number of open flowers) was also altered by an interaction between these two effects. Changes in floral traits translated into overall greater use of low-resistance, undamaged plants based on total amount of time pollinators spent foraging on plants. Total numbers of pollinators attracted to plants did not differ among treatments; however, pollinators spent significantly more time per flower on plants from the low-resistance population and tended to visit more flowers on these plants as well. Previous work by other investigators on the same pollinator taxa has shown that longer visit times are associated with greater male and female plant fitness. Because initial numbers of pollinators did not differ between selection regimes, palatability and/or amount of rewards offered by high- and low-resistance populations are likely to be responsible for these patterns. During periods of pollinator limitation, less defended plants may have a selective advantage and pollinator preferences may mediate directional selection imposed by herbivores. In addition, if pollinator preferences limit seed set in highly defended plants, then lower seed set previously attributed to allocation costs of defense may also reflect greater pollinator limitation in these plants relative to less defended plants.     

INSECT RESISTANCE TO INSECTICIDES AND DYNAMICS OF INSECT TOXICOLOGY

Abstract  In field control of insects with insecticides, insects could develop different degrees of resistance. When resistance data were reviewed more extensively, it was found that detoxication alone cannot explain very high resistance of house flies to OC1 (organochlorine) insecticides. As a group, flies can develop much higher resistance to OC1 than to OP (organophosphorus) insecticides. although OPs are generally less stable in insects. With the consideration of the dynamics of insect toxicology. one can readily realize the importance of penetration. Based on the rates of penetration and detoxication. slow penetration is a limiting factor for detoxication. To further explain the observed results on the control of S (susceptible) 'and R (resistant) insects, several correlation curves were plotted. on the relationship between physical and biological factors. These relationships not only indicate approximate degrees of resistance of flies to OPs and OCls, but also help select new toxicants. For example, fast speed of action index of insecticides can produce lower resistance, and the analysis of the joint action of insecticides helps evaluate the types (same or different) of mode of action for controlling resistant insects.     

ABSOLUTE VERSUS RELATIVE MEASUREMENTS OF SEXUAL SELECTION: ASSESSING THE CONTRIBUTIONS OF ULTRASONIC SIGNAL CHARACTERS TO MATE ATTRACTION IN LESSER WAX MOTHS,ACHROIA GRISELLA (LEPIDOPTERA: PYRALIDAE)

When females choose a mate among a group of signaling males concentrated in a small area, a male's mating success is often determined not only by his absolute attractiveness but by the attractiveness of his neighbors as well. Multivariate analyses of sexual selection measurements based on absolute values of predictor variables are then misleading, because such analyses assume that the fitness of a given individual is not influenced by others. We addressed this problem of relative fitness in sexual selection by developing two adjustments of the predictor variables in the multivariate analyses by including group means in addition to absolute values and by using relative values, deviations from group means. In the lesser wax moth, Achroia grisella (Lepidoptera: Pyralidae), aggregated males produce ultrasonic signals attractive to females in the vicinity of honey bee colonies. Playback experiments showed that females prefer signals whose pulses are louder, longer, delivered at a faster rate, and include lengthy silent gaps within pulse pairs (long asynchrony intervals). To measure sexual selection on ultrasonic signals, attractiveness was assessed by observing the number of females orienting toward given males in four-choice trials. The various signal characters of the males were computed from ultrasound recordings. Multivariate regression and nonparametric analyses revealed that peak amplitude, asynchrony interval, and pulse rate were the direct targets of selection. Nonlinear stabilizing and correlational selection were also detected. Comparisons of results from multivariate analyses based on absolute values and on the two relative adjustments indicated that the quality of a four-male group did not affect the strength or direction of linear selection but changed the strength of nonlinear selection. Both relative adjustments improved the prediction of male attractiveness. Three-dimensional surface plots generated by the nonparametric regression analyses showed that attractiveness increased monotonically with any combination of the signal characters. This graphical technique also showed that female choice in A. grisella was based on a relative, as opposed to a threshold, decision rule. Overall, male attractiveness for the population remained consistent between testing days. However, attractiveness values for some individual males changed between successive testing days. In these cases, the change in attractiveness was related only to the change in peak amplitude.     

昆虫抗药性和昆虫毒理动力学(英文)

不断地使用一种杀虫药剂防治昆虫,会导致昆虫产生抗药性。对昆虫抗药性资料进行广泛综述时,发现了仅单独的解毒作用不能被解释为家蝇对有机氯杀虫药剂产生高抗性原因。作为一个基因。家蝇可以对有机氯产生比对有机磷杀虫剂更高的抗药性,尽管有机磷杀虫剂一般在虫体内是不太稳定的。考虑到昆虫毒理的动力学,杀虫药剂的穿透作用更显示出其实际的重要性。根据穿透和解毒的速率,慢的穿透作用是解毒作用的一个限制因子。防治敏感和抗性昆虫的观察结果,可以划出物理和生物因子之间关系的几种相关曲线图解。这些相关性不仅能说明家蝇对有机磷和有机氯杀虫剂的抗性程度,而且也助于选择出新的杀虫毒剂。     

二苯基脲磺酸钙对小麦苗抗旱性的影响

用浓度为100mgL^-1的二苯基脲磺酸钙溶液喷小麦苗期叶片,能明显增加小麦幼苗的过氧化物酶、过氧化氢酶和超氧化物岐化酶的活性,并使保水力和复活能力增强。用100mgL^-1DSC拌种,还可提高小麦种子在干旱条件下的萌发率。