A population and energy model of a forest insect outbreak

A model is proposed for the dynamics of a forest insect population with account of food consumption and the response of plants to damage. Equations are derived relating the propagation coefficient, female mass, pest conversion efficacy, and plant reaction. Outbreak scenarios are analyzed as dependent on steady-state female weight. The results are compared with the data of observations in nature.     

Electrical resistance of labellar taste hairs in the blowfly, Phormia regina M., as a function of age and sex

The electrical resistance of the labellar taste hairs of Phormia regina M. is enhanced by aging in both males and females; this increase is greater in males. Resistance variations, related to changes in response of stimulated chemoreceptors, may explain, at least in part, the reduction in reflex food intake, O2 consumption, weight increase and, on the whole, survival capabilities of males vis-à-vis female insects.     

唾液成分在刺吸式昆虫与植物关系中的作用

近年来,人们对刺吸式昆虫唾液成分的研究,揭示出其在刺吸式昆虫与植物关系中的重要作用。对多数刺吸式昆虫而言,他们取食时会分泌胶状和水状两种唾液,其中胶状唾液会在取食早期分泌形成唾液鞘来围绕并保护口针,通过直接和间接的作用来帮助取食;而水状唾液中则包含了果胶酶、纤维素酶、多酚氧化酶、过氧化物酶、碱性磷酸酯酶、蔗糖酶等组分,来帮助刺吸式昆虫对植物穿刺、消化食物、解毒次生物质并破坏植物的防御反应。有趣的是,唾液成分同时还可以诱导植物的防御反应,包括诱导植物的伤信号引起直接防御反应和诱导植物产生挥发物吸引植食者的天敌引起间接防御反应。并且,许多刺吸式昆虫取 食能够特异性地引发植物的病理反应,有研究推测刺吸式昆虫唾液中多聚半乳糖醛酸酶、碱性磷酸酯酶、蔗糖酶、多酚氧化酶等成分可能是某些植物特定病理反应的激发子,但是目前还没有定论,同时许多刺吸式昆虫唾液中的氨基酸和蛋白酶还是引起植物虫瘿的原因之一。 迄今的研究表明,刺吸式昆虫会根据不同的寄主植物和不同的生理需要,通过唾液组分的改变,来达到取食和发育的目的。对刺吸式昆虫唾液成分和作用机理的研究,可以为揭示刺吸式昆虫致害机理特别是传毒机理、指导害虫有效治理、阐明其与植物的协同进化等提供一定的思路。     

小良热带人工阔叶混交林中屋顶鼠施氏亚种的食性及其生态学意义

Rattus rattus slandeni的食性资料是在小良人工阔叶混交林中通过200个鼠箱观察残留食物的方法收集到的。屋顶鼠摄食植物39种,主要为果实、种子部分,并大量捕食金龟子、蝉和蝗虫等昆虫,偶尔捕食小脊椎动物。植物性和动物性两大类残食的总出现率相近,5-10月以动物性食物为主,11-4月以植物性食物为主。该鼠搬运和遗弃果实、种子的行为,有助于植物种类的传布,大量捕食害虫,有利于该系统的生态平衡,故对其益害问题应作客观评价。     

Identification of a tachykinin-related peptide with orexigenic properties in the German cockroach

A number of evidences suggest that tachykinin-related peptides (TRPs) of insects can stimulate food consumption after being released from the midgut to the hemolymph. The idea of the present work has been to test this hypothesis in the anautogenous cockroach Blattella germanica. First, we have identified the peptide LemTRP-1 (APSGFLGVR-NH(2)) from brain extracts, by means of an ELISA developed with a polyclonal antibody against this peptide. ELISA studies have also shown that, whereas brain LemTRP-1 levels were fairly constant, midgut levels increase to a maximum on day 3 after adult emergence, falling thereafter until the end of the gonadotrophic cycle. Interestingly, maximum values of food consumption are concomitant with the decrease of LemTRP-1 immunoreactivity in the midgut. Furthermore, starvation decreases LemTRP-1 immunoreactivity in midgut, whereas in the hemolymph it increases. Finally, injection of synthetic LemTRP-1 to adult females significantly stimulates food consumption. The whole observations suggest that LemTRP-1 is released from the midgut to the hemolymph when sustained food consumption is required to maintain vitellogenesis at the highest levels, and that LemTRP-1 in the hemolymph stimulates food consumption in these days.     

Molecular strategies of plant defense and insect counter-defense

The prediction of human population growth worldwide indicates there will be a need to substantially increase food production in order to meet the demand on food supply.This can be achieved in part by the effective management of insect pests. Since plants have co-evolved with herbivorous insects for millions of years, they have developed an array of defense genes to protect themselves against a wide variety of chewing and sucking insects.Using these naturally-occurring genes via genetic engineering represents an environmentally friendly insect pest-control measure. Insects, however, have been actively evolving adaptive mechanisms to evade natural plant defenses. Such evolved adaptability undoubtedly has helped insects during the last century to rapidly overcome a great many humanimposed management practices and agents, including chemical insecticides and genetically engineered plants. Thus, better understanding of the molecular and genetic basis of plant defense and insect counter-defense mechanisms is imperative, not only from a basic science perspective, but also for biotechnology-based pest control practice. In this review, we emphasize the recent advance and understanding of molecular strategies of attack-counterattack and defense-counter-defense between plants and their herbivores.     

转基因抗虫作物对非靶标昆虫的影响

转基因抗虫作物自 1996年被批准商业化种植以来 ,它的抗虫性和经济效益已得到了普遍肯定 ,同时 ,转基因抗虫作物对非靶标生物的影响 ,如转基因抗虫作物的长期种植 ,是否会导致次要害虫上升为主要害虫 ,是否会影响有益昆虫 ,包括重要经济昆虫、捕食性和寄生性天敌以及重要蝶类的种类及种群数量 ,已成为转基因抗虫作物生态风险评估的重要内容。一些研究结果表明 ,转基因抗虫作物在对靶标害虫有效控制的同时 ,一些对杀虫蛋白不敏感的非靶标害虫有加重危害的趋势 ,由于种植转基因抗虫作物 ,减少了化学农药的使用 ,客观上也使非靶标害虫种群数量上升 ,这对转基因抗虫作物害虫综合治理提出了新的要求。靶标害虫数量的减少直接影响了害虫天敌种群数量 ,靶标害虫取食转基因抗虫作物后发育迟缓 ,也间接影响了天敌昆虫的生长发育 ,转基因抗虫作物的花粉或花蜜是一些重要经济昆虫如蜜蜂、熊蜂和一些寄生蜂 ,甚至捕食性天敌的食物来源 ,或花粉飘落到一些鳞翅目昆虫如家蚕或重要蝶类昆虫的寄主植物上 ,直接或间接对这些昆虫造成一定影响。目前大多数研究表明转基因抗虫作物对非靶标昆虫 ,特别是对有益昆虫没有明显的不利影响 ,也有研究报道认为对某些有益昆虫有一定的不良影响。这为深入开展转基因抗虫作物的生态安全     

Effects of adult‐derived carbohydrates and amino acids on the reproduction of Plutella xylostella

The use of floral resources to improve the efficiency of natural enemies has grown in recent years, although their effect on pest populations has been overlooked. To understand how access to food resources by adults of Plutella xylostella (L.) (Lepidoptera: Plutellidae) affects their reproduction, the effects of amino acids and carbohydrates (i.e. fructose, glucose and sucrose) on the longevity, lifetime fecundity, egg viability and population growth of this important pest of brassicas are evaluated. Carbohydrate intake increases longevity, oviposition period and lifetime fecundity of P. xylostella. Oviposition period and fecundity are six‐fold higher in females that consumed carbohydrates. By contrast, amino acid intake by adults does not affect reproductive parameters, even when mixed with carbohydrates. The estimated demographic parameters indicate that the adult diet is important for pest population growth because the net reproductive rate and the intrinsic rate of increase are higher when females have access to carbohydrates. These results are important from both physiological and ecological points of view. The increasing use of flowering plants as a microhabitat and food source for natural enemies may also result in benefits for herbivorous insects, compromising any success in pest control.     

Edible insects in China: Utilization and prospects

The use of edible insects has a long history in China, where they have been consumed for more than 2000 years. In general, the level of acceptance is high for the consumption of insects in China. Many studies on edible insects have been conducted in the last 20 years, and the scope of the research includes the culture of entomophagy and the identification, nutritional value, farming and breeding of edible insects, in addition to food production and safety. Currently, 324 species of insects from 11 orders are documented that are either edible or associated with entomophagy in China, which include the common edible species, some less commonly consumed species and some medicinal insects. However, only approximately 10 to 20 types of insects are regularly consumed. The nutritional values for 174 species are available in China, including edible, feed and medicinal species. Although the nutritional values vary among species, all the insects examined contain protein, fat, vitamins and minerals at levels that meet human nutritional requirements. Edible insects were, and continue to be, consumed by different ethnic groups in many parts of China. People directly consume insects or food products made from insects. The processing of products from insect protein powder, oil and chitin, and the development of healthcare foods has been studied in China. People also consume insects indirectly by eating livestock that were fed insects, which may be a more acceptable pathway to use insects in human diets. Although limited, the data on the food safety of insects indicate that insects are safe for food or feed. Incidences of allergic reactions after consuming silkworm pupae, cicadas and crickets have been reported in China. Insect farming is a unique breeding industry in rural China and is a source of income for local people. Insects are reared and bred for human food, medicine and animal feed using two approaches in China: the insects are either fully domesticated and reared completely in captivity or are partially raised in captivity, and the insect habitat is manipulated to increase production. Depending on the type of relationship the insect has with humans, plants and the environment, different farming strategies are used. The social and scientific communities must work together to promote the use of insects as food and feed.     

Correlation and regression studies between pupal weight and fecundity of muga silkworm Antheraea assama Westwood (Lepidoptera: Saturniidae) on four different foodplants.

Female pupal weight and fecundity of mother moth of Antheraea assama Westwood fed with four different food plants have been studied. Litsaea polyantha fed females showed significantly higher pupal weight and higher rate of oviposition in comparison to three food plants Machilus bombycina, Litsaea salicifolia and Cinnamomum glaucescens. The number of eggs laid was correlated with the pupal weight. The correlation co-efficient (r = 0.9730) showed positive and significant correlation at 1% level. The pupal weight was found to be the best and genuine estimator of fecundity.     

Nutritional indices in the gypsy moth (Lymantria dispar (L.)) under field conditions and host switching situations

A large proportion of gypsy moths (Lymantria dispar (L.)) are likely to experience multiple species diets in the field due to natural wandering and host switching which occurs with these insects. Nutritional indices in fourth and fifth instar gypsy moth larvae were studied in the field for insects that were switched to a second host species when they were fourth instars. The tree species used as hosts were northern pin oak (Quercus ellipsoidalis E. J. Hill), white oak (Q. alba L.), big-tooth aspen (Populus grandidentata Michx.), and trembling aspen (P. tremuloides Michx.). Conclusions of this study include: 1) Insects which fed before the host switch on northern pin oak performed better after the host switch than did insects with other types of early dietary experience. While the northern pin oak-started insects had very low relative food consumption rates on their second host species immediately after the switch, one instar later they had the highest ranked consumption rates. During both instars they had the second highest efficiencies of converting ingested and digested food to body mass. High food consumption rates and relatively high efficiency of food conversion helped these insects to obtain the highest ranked mean relative growth rates in the fifth instar compared to the relative growth rates obtained by insects from any of the other first host species. 2) Among the four host species examined, a second host of trembling aspen was most advantageous for the insects. Feeding on this species after the switch led to higher larval weights and higher relative growth rates for insects than did any of the other second host species. The insects on trembling aspen attained excellent growth despite only mediocre to low food conversion efficiencies. The low efficiencies were offset by high relative food consumption rates. 3) Low food consumption rates often tend to be paired with high efficiency of conversion and vice versa. 4) There is no discernable tendency for the first plant species eaten to cause long-term inductions which affect the ability of gypsy moths to utilize subsequent host plants. Insects did not tend to consume more, grow faster, or be more efficient if their second host plant was either the same as their rearing plant or congeneric to it. Methods are delineated which allow values of nutritional indices to be obtained for insects on intact host plants under field conditions. These methods are useful for the purpose of answering questions about the relative effects that different diet treatments have on insect response.     

Response of the polyphagous whitefly Bemisia tabaci B-biotype (Hemiptera: Aleyrodidae) to crop diversification - influence of multiple sensory stimuli on activity and fecundity

A fundamental question concerning crop diversification is which mechanisms determine pest population size in polycultures compared to monocultures. It has been proposed that polyphagous insects experience a difficulty in decision-making when selecting food and oviposition sites in the presence of different host plants. This hypothesis was tested in the extremely polyphagous whitefly Bemisia tabaci (Gennadius) B-biotype, where behaviour (movement) and fecundity of females were compared in choice and no-choice experiments in the laboratory. Two parallel tests, one on different crops, including cucumber, bean and tomato, and one on different tomato cultivars, were conducted using both a mixture of crops and of tomato cultivars, as opposed to the same crop or cultivar respectively. Bemisia tabaci showed a distinct behavioural preference for cucumber when exposed to different crops simultaneously suggesting that B. tabaci has no difficulty in choosing a host plant, i.e. in making a decision, when one of the plants offered in the choice test is a high-ranking host plant. Conversely, when only low-ranking hosts of similar, but not identical, signatures were present, female whiteflies appeared to have difficulty in making a decision, resulting in increased movement and reduced fecundity. This is consistent with both the hypothesis that polyphagous insects have a problem selecting a host plant when given multiple choices and with the hierarchy threshold model, under which egg loads are lessened between periods of searching for better host plants. The study illustrates how insect behaviour can be affected by inter-cropping not only with different crops, but also with different cultivars of the same crop, thus potentially providing a simple and efficient way of reducing whitefly population build-up.     

Increase in tannin consumption by sifaka (<Emphasis Type="Italic">Propithecus verreauxi verreauxi</Emphasis>) females during the birth season: a case for self-medication in prosimians?

In this study we report preliminary data on the consumption of tannin-rich plants by sifakas (Propithecus verreauxi verreauxi) living in the Kirindy forest, western Madagascar. Sifakas spent most of their time feeding on only a few plant species. The tannin intake during the period between the pregnancy and birth season was significantly higher in pregnant females or females with lactating infants than in non-reproductive females and males. These periparturient females secured a larger proportion of condensed tannins by short feeding bouts on plants not included in the group's limited preferred food species. The measured increase in tannin intake is puzzling in light of the fact that tannins are commonly known for their protein-binding properties. Since protein demands are highest in pregnant and lactating females, possible medicinal benefits of tannin ingestion are considered. Tannin consumption is associated with an increase in body weight and stimulation of milk secretion. Veterinarians administer tannins as an astringent, anti-hemorrhagic and anti-abortive. Their high potential as an alternative anthelminthic has also recently been recognized. Thus, when viewed as self-medicating behavior, controlled increase in tannin intake could have multiple prophylactic advantages for females during the periparturient period. The high selectivity in their plant choice, and the presence of unusual feeding habits by a particular group of individuals (females with infants) limited in time (birth season), suggests that an increase in tannin ingestion may be a self-medicating behavior with multiple directly adaptive benefits to female reproduction. Electronic Publication     

Inhibition of thyroxine binding to adenohypophysial proteins in vitro by 2,4-dinitrophenol administered in vivo.

Male and female rats were given oestradiol benzoate (1 mg as a microcrystal aqueous suspension i.m. twice a week), 0.0033% 2.4-dinitrophenol (DNP) in their food (about 1 mg/rat/day), or 0.1% DNP in their food (about 30 mg/rat/day), or both oestradiol and DNP. The smaller DNP dose mildly stimulated food consumption and did not affect body weight. The larger dose strongly inhibited food consumption in the first two weeks of the experiment; consumption then returned to the control level, but body weight fell markedly at the same time. After 3 weeks' administration of both the small and the large dose of DNP, adrenal weight in the males was raised and the weight of the gonads was unchanged. The large DNP dose severely reduced the weight of the seminal vesicles and the uteri. It also inhibited the accumulation of radioiodine in the thyroid of both males and females. Isolated administration of the oestrogen raised adrenal weight in the males and ovarian and uterine weight in the females; it reduced the weight of the testes and seminal vesicles. These reactions were not affected by DNP. A pronounced oestradiol-induced increase in the weight of the adenohypophyses was accompanied by raised thyroxine binding to the adenohypophysial proteins in vitro. DNP inhibited the growth reaction of the adenohypophysis to the oestrogen only slightly and non-significantly, but significantly inhibited the thyroxine binding reaction to the adenohypophysial proteins in vitro. By itself, DNP had no effect on adenohypophysial weight, but reduced thyroxine binding to the adenohypophysial proteins in vitro, especially in males. The effect of DNP was similar to that of thyroxine observed in earlier experiments; nothing is known of its mechanism.     

Females of Cotesia vestalis,a parasitoid of diamondback moth larvae,learn to recognise cues from aphid‐infested plants to exploit honeydew

1. To maximise their reproductive success, the females of most parasitoids must not only forage for hosts but must also find suitable food sources. These may be nectar and pollen from plants, heamolymph from hosts and/or honeydew from homopterous insects such as aphids. 2. Under laboratory conditions, females of Cotesia vestalis, a larval parasitoid of the diamondback moth (Plutella xylostella) which does not feed on host blood, survived significantly longer when held with cruciferous plants infested with non‐host green peach aphids (Myzus persicae) than when held with only uninfested plants. 3. Naïve parasitoids exhibited no preference between aphid‐infested and uninfested plants in a dual‐choice test, but those that had been previously fed aphid honeydew significantly preferred aphid‐infested plants to uninfested ones. 4. These results suggest that parasitoids that do not use aphids as hosts have the potential ability to learn cues from aphid‐infested plants when foraging for food. This flexible foraging behaviour could allow them to increase their lifetime reproductive success.     

Dynamics of energy metabolism in ontogenesis of striped shield bug (Graphosoma lineatum L.) and cabbage moth (Mamestra brassicae L.)

Dynamics of growth and oxygen consumption during ontogenesis of insects with direct (striped shield bug Graphosoma lineatum L.) and indirect (cabbage moth Mamestra brassicae L.) development have been compared. The correlation between a character of energy metabolism alteration and peculiarities of development of the insects has been shown. Cyclic decrease of oxygen consumption during molt and sharp dropping during metamorphosis have been observed in insects with indirect development. The decrease of oxygen consumption has been observed in insects with direct development only during molts. The coefficient a of allometric dependence of oxygen consumption on body weight of imago for cabbage moth was two times higher than that for striped shield bug.     

昆虫唾液成分在昆虫与植物关系中的作用

近年来,人们对于植食性昆虫唾液的深入研究,揭示出其在昆虫与植物的相互关系和协同进化中起到非常重要的作用。植食性昆虫唾液中含有的酶类和各种有机成分,能诱导植物的一系列生化反应,而且这些反应有很强的特异性,与为害的昆虫种类甚至龄期有关。鳞翅目幼虫口腔分泌物（或反吐液）中含有的β-葡糖苷酶、葡萄糖氧化酶等酶类和挥发物诱导素等有机成分,已经证明可以诱导植物的反应; 刺吸式昆虫的取食也可以刺激植物产生反应,但其唾液内的酶类,如烟粉虱的碱性磷酸酶, 蚜虫的酚氧化酶、果胶酶和多聚半乳糖醛酸酶, 蝽类的寡聚半乳糖醛酸酶等是否发挥作用,目前还没有直接的证据。寄主植物对昆虫的唾液成分也有很大的影响,可能是昆虫对不同植物营养成分和毒性成分的适应方式。对昆虫唾液蛋白的分析表明,具有同样类型口器、食物类型接近的昆虫,唾液成分有更多的相似性。研究植食性昆虫的唾液成分,对于阐明昆虫和植物的协同进化关系、昆虫生物型的形成机理、害虫的致害机理,以及指导害虫防治等,有着一定的理论和实际意义。     

Biodiversity and stability of herbivore populations: influences of the spatial sparseness of food plants

Returning to the classical diversity–stability problem about population densities, we propose a hypothesis that the spatial sparseness of food plants of herbivores, which is frequently observed in diversified communities such as those in the tropics, may be a potential source of the low variability in herbivore densities. The hypothesis consists of the following components: (1) sparseness of food plants of several herbivores increases with increasing number of plant species in a given amount of area, (2) spatial sparseness of food plants reduces the dispersal rate of herbivores between food plants, (3) such a decrease in dispersal rate causes a larger spatial variance in the consumption rate of food plants, (4) such a large spatial variance in the consumption rate of food plants reduces the temporal variance in the amount of food plants, and (5) the reduced temporal variance in the amount of food plants yields a smaller variance in the temporal dynamics of herbivores. A simple mathematical model was constructed to show a theoretical basis of the fourth component of the hypothesis. To exemplify the second, third, and fourth components of the hypothesis in fields, we conducted field experiments on the interaction between butterfly larvae and cabbages, in which cabbage seedlings were planted by two levels of sparseness: 1 m apart and 0.2 m apart. The spatial variance in the amount of leaf dry weight that escaped from larval feeding was larger in sparsely planted fields, which was in accordance with the third component of the hypothesis. The variability in the mean amount of leaf dry weight was smaller in sparsely planted fields, which was in accordance with the fourth component of the hypothesis. Received: June 14, 2001 / Accepted: February 14, 2002     

Dynamics of energy metabolism in ontogenesis of striped shield bug (<Emphasis Type="Italic">Graphosoma lineatum</Emphasis> L.) and cabbage moth (<Emphasis Type="Italic">Mamestra brassicae</Emphasis> L.)

Dynamics of growth and oxygen consumption during ontogenesis of insects with direct (striped shield bug Graphosoma lineatum L.) and indirect (cabbage moth Mamestra brassicae L.) development have been compared. The correlation between a character of energy metabolism alteration and peculiarities of development of the insects has been shown. Cyclic decrease of oxygen consumption during molt and sharp dropping during metamorphosis have been observed in insects with indirect development. The decrease of oxygen consumption has been observed in insects with direct development only during molts. The coefficient a of allometric dependence of oxygen consumption on body weight of imago for cabbage moth was two times higher than that for striped shield bug.