Bird predation as a selective pressure on the immature stages of the cabbage butterflies, Pieris rapae and P. brassicae

The importance of bird predation as a selective pressure on the eggs, larvae and pupae of the cabbage butterflies, Pieris rapae L. and P. brassicae L. has been investigated in a rural garden and an allotment. Birds are the main predators of all stages in a well-tended garden whereas in a field the eggs and young larvae are mainly preyed upon by arthropods. The species of avian predators vary according to the stage of development and species of prey. Consequently the relative survival rate of P. rupae and P. brussicue varies with stage of development. This changing pattern of survival has in turn acted as a selective pressure on their two main braconid parasites. Many aspects of the size, shape, colour and behaviour of the larvae and pupae of both species of Pieris appear to be adaptations to the selective pressures exerted by bird predation.     

New records of natural enemies of Plutella xylostella (L.) (Lepidoptera: Plutellidae) in Pernambuco, Brazil

We report the occurrence of natural enemies of Plutella xylostela (L.) in organically farmed kale in Pernambuco, Brazil. Seven natural enemies were observed parasitizing or preying on larvae and pupae of P. xylostella--three parasitoids: Cotesia plutellae Kurdjumov (Hym.: Braconidae), Conura pseudofulvovariegata (Becker) (Hym.: Chalcididae) and Tetrastichus howardi (Olliff) (Hym.: Eulophidae), and four predators: Cheiracanthium inclusum (Hentz) (Araneae: Miturgidae), Pheidole sp.Westwood (Hym.: Formicidae), nymphs and adults of Podisus nigrispinus (Dallas) (Hem.: Pentatomidae), and one unidentified species of solitary wasp. Beyond recording these natural enemies, data on predation of P. xylostella larvae in the field and laboratory by C. inclusum are presented.     

Mortality of eggs, larvae and pupae and larval dispersal of the cabbage moth, Mamestra brassicae, in white cabbage in south-eastern Norway

The mortality of eggs, larvae and pupae and larval dispersal of the cabbage moth, Mamestra brassicae (L.) (Lepidoptera: Noctuidae) was investigated in a series of small-scale field experiments in white cabbage, Brassicae oleracea var. capitata (L.), and in the laboratory during 1990–1992 in south–eastern Norway. The highest mortality was found in young larvae and in hibernating pupae. In 1990, larval mortality in the first instar was 80% (range 9–97% for the individual cohorts). Most larvae died within the first 1–3 days after hatching. The dispersal activity during these days was high, and failure to establish feeding sites and predation were probably the main mortality causes. Pupal mortality during winter was 90% on average for 1990–1993 (range 81–100%). The main mortality factor was probably unfavourable weather conditions, and indications of cold stress were found. The impact from parasitoids and diseases was generally low. Trichogramma semblidis (Aurivillius) (Trichogrammatidae) was reared from M. brassicae eggs in very low numbers in 1991. Larval parasitism increased from < 1% in 1990 to almost 24% in 1992, and was almost totally caused by the braconids Microplitis mediator (Haliday) and Aleiodes (Aleiodes) sp. Predation of frozen larvae on the soil surface was 75% on average (range 63–96%) during 1990–1992 in first instar larvae and decreased gradually with larval age. The consumption rates of Philonthus atratus (Gravenhorst) (Staphylinidae) and the carabids Bembidion tetracolum (Say), Pterostichus melanarius (Illiger) and Harpalus rufipes (Degeer) on M. brassicae eggs and larvae were investigated in non-choice experiments in the laboratory. A preliminary survival model based on estimates of the mortality factors identified in this study is presented.     

Relationship between predation by Podisus nigrispinus and developmental phase and density of its prey,Plutella xylostella

This study evaluated the predation by Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) at various densities of larvae and pupae of the pest Plutella xylostella (L.) (Lepidoptera: Plutellidae). We tested predator behavior of female P. nigrispinus at six experimental densities (1, 5, 10, 15, 20, or 25 prey items in a 1‐l transparent plastic container, replicated 15 times for each density) of both the fourth instar and pupae of P. xylostella. The number of prey consumed was monitored every 15 min for 12 h and was subsequently monitored at 24 h. Podisus nigrispinus females were weighed before and after the experiments to determine the effect of different densities of prey on their weight gain. Female predators had a Type‐II functional response, with attack rate estimated at 1.387 and 0.260 and a handling time of 0.091 and 0.183 h^?1 for larvae and pupae, respectively. Podisus nigrispinus consumed on average 10.9 larvae or 5.5 pupae in 24 h. Despite the similarity of the response type, P. nigrispinus preferred to feed on larvae, rather than on pupae.     

Pre-adult mortality in the blowfly Lucilia sericata

Populations of the blowfly, Lucilia sericata (Meigen) (Diptera: Calliphoridae), have a considerable potential for rapid increase; the lifetime reproductive output of each adult female has been estimated to be between 130 and 172 eggs. Nevertheless, in the field, absolute population densities of this species are relatively low. To account for this difference, the levels of mortality affecting the eggs, feeding and wandering larvae and pupae of L. sericata were assessed in the field and laboratory. Percentage egg hatch was dependent on relative humidity with no egg eclosion at humidities below 50%; there was no significant effect of temperature on egg hatch. On infested sheep, the mean mortality of feeding larvae was 53%, but this ranged widely from 0% to 96%. There was no effect of atmospheric temperature or humidity on the mortality of feeding larvae in vivo. In the laboratory, only 10% of wandering larvae pupariated at 10 degrees C. At above 20 degrees C pupariation was consistently almost 100%. Percentage emergence increased from 0% at 10 degrees C to about 80% between 20 and 30 degrees C. The upper lethal temperature for pupae was approached at 35 degrees C. Analysis of the predation of pupae in the field revealed a weak, but significant curvilinear relationship between temperature and proportionate mortality and a median mortality of 0.49% per 24 h exposure (interquartile range = 5.2%). There was no evidence of density dependence in pupal predation. Overall, it is estimated that pre-adult mortality accounts for losses of approximately 97% of each generation, but this figure is subject to considerable variation depending on factors such as climate, time of year and host susceptibility.     

Effects of alternative food on cannibalism and herbivore suppression by carabid larvae

1. Predator and alternative food density are important factors influencing herbivore suppression by generalist predators. Herbivore suppression can be reduced if predators forage preferentially on alternative foods. Cannibalism can increase at high predator densities, further reducing herbivore suppression. However, complex interactions are possible, as alternative food can increase predator abundance and survival restoring top‐down effects on herbivores. 2. In two species of carabid larvae (Poecilus chalcites and Anisodactylus ovularis), we studied how alternative foods (fly pupae and grass seeds) and predator density affect predation of black cutworm larvae and how alternative foods affect cannibalism among carabid larvae. 3. Adding alternative food to microcosms generally reduced total predation of cutworms. However, the strength of this effect was dependent on carabid species, larval density, and food type. 4. Increasing larval density from one to three per microcosm reduced per‐capita predation by both species irrespective of alternative food treatment. 5. Alternative food reduced cannibalism in both carabid species and increased survival of carabid larvae in field plots, such that twice as many were captured in plots subsidised with pupae than plots with no alternative food. 6. These results provide new insight into the complex interactions that influence predator survival and herbivore suppression in resource diverse habitats by demonstrating the primacy of intraguild interactions among carabid larvae.     

黄曲条跳甲室内饲养方法的改进

介绍一种饲养黄曲条跳甲Phyllotreta striolata(Fabricius)的改进新方法,采用分隔式养虫笼饲养成虫和萝卜"凹"型孔饲养幼虫,结果表明,使用该方法进行饲养,卵的成活率可达89.3%,1~3龄幼虫的存活率为65.0%~70.0%,蛹的存活率达80.0%,可以有效实现黄曲条跳甲的室内饲养。     

温度对丝带凤蝶生长发育的影响

温度对丝带凤蝶生长发育的研究。结果表明,丝带凤蝶在武汉地区1年发生6代。在15~35℃范围内,卵孵化率、幼虫和蛹存活率分别在25,25和20℃时最高,卵、幼虫和蛹发育历期随温度升高显著缩短;适宜发育温度范围为20~35℃。丝带凤蝶卵、幼虫和蛹的发育起点温度分别约为(8.7±2.5)℃、(11.9±6.0)℃和(6.9±1.8)℃,有效积温分别约为(82.5±5.1),(222.2±39.5)和(178.7±7.3)日.度。     

Survival and development of immature stages of the Mediterranean fruit fly (Diptera: Tephritidae) in citrus fruit

We studied, under laboratory conditions, the performance of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), immature stages in intact whole fruit of three sweet orange varieties, lemon, and bitter oranges. Both citrus variety and fruit part (flavedo, albedo, and pulp) had strong effects on larval performance, smaller effects on pupae, and no effects on eggs. Fruit peel was the most critical parameter for larval development and survival, drastically affecting larval survival (inducing very high mortality rates). Among fruit regions, survival of larvae placed in flavedo was zero for all varieties tested except for bitter orange (22.5% survival), whereas survival in albedo was very low (9.8-17.4%) for all varieties except for bitter orange (76%). Survival of pupae obtained from larvae placed in the above-mentioned fruit regions was high for all varieties tested (81.1-90.7%). Fruit pulp of all citrus fruit tested was favorable for larval development. The highest survival was observed on bitter oranges, but the shortest developmental times and heaviest pupae were obtained from orange cultivars. Pulp chemical properties, such as soluble solid contents, acidity, and pH had rather small effects on larval and pupal survival and developmental time (except for juice pH on larvae developmental duration), but they had significant effects on pupal weight.     

Interspecific interactions in a tri-trophic arthropod system: effects of a spider on the survival of larvae of three predatory ladybirds in relation to aphids

The effects of the crab spider, Misumenops tricuspidatus (Fabricius), on the larval survival of three ladybird species, Harmonia axyridis Pallas, Coccinella septempunctata L., and Propylea japonica L., in relation to aphids were investigated in the laboratory. Predation by the spider on the three ladybird species differed. All the larvae of C. septempunctata, none of H. axyridis, and an intermediate number of P. japonica were attacked and eaten by the spider. All the larvae of H. axyridis suffered mortality due to cannibalism or starvation in the treatments with and without a spider. In case of C. septempunctata, however, mortality in the early instars was significantly greater in the treatment with a spider than without a spider and no larvae developed into pupae due to predation. In the treatment without a spider, the majority of the larvae in the former treatment suffered mortality due to cannibalism or starvation, and only 13.3% of larvae developed into the adult stage. In the case of P. japonica, mortality was mainly attributed to predation in the treatment with a spider and only 26.7% became adult. In comparison, 86.7% of larvae survived to the adult stage in the treatment without a spider. In addition, in both H. axyridis and C. septempunctata, the development of young larvae was significantly slower in the presence of a spider, but this was not the case with the older larvae of H. axyridis, which indicates that the effect of the spider on larval development changed with the developmental stage of the larvae in this species. However, the spider had no significant effect on the developmental time of P. japonica larvae. Although both the spider and the ladybirds significantly affected the number of aphids, they did not have an additive effect on aphid abundance. The interactions between the spider and the ladybirds, such as intraguild predation or competition, caused them to reduce aphid population density less than the ladybirds did on their own. The effect of the spider on the larval performance of three predatory ladybirds was found to be unequal in terms of their vulnerability to predation and rate of larval development and it depended on the species and developmental stage of the ladybird.     

Effect of emigration on cannibalism and intraguild predation in aphidophagous ladybirds

Abstract.  1. The incidence and timing of emigration, cannibalism, and intraguild predation of larvae of three aphidophagous ladybirds (Coleoptera: Coccinellidae), Harmonia axyridis Pallas, Coccinella septempunctata brucki Mulsant, and Propylea japonica Mulsant, relative to the presence of prey was determined in the laboratory in single- and mixed-species populations.
2. In single-species populations, 80% of the larvae of C. s. brucki emigrated prior to the extinction of the aphid population and no larvae were lost due to cannibalism; however > 80% of the larvae of the other two species were still present when the aphid became extinct and the losses due to cannibalism for H. axyridis and P. japonica were 25% and 14% respectively. Finally, 28% of the P. japonica larvae completed their development, whereas no larvae of the other two species became adult.
3. In mixed-species populations, mortality of P. japonica attributable to cannibalism or intraguild predation increased greatly to 60%, whereas that of the other two species remained about the same. Consequently, survival of H. axyridis larvae improved and survival of P. japonica worsened; however the survival of C. s. brucki larvae was not affected by the other two species. Early emigration by C. s. brucki larvae may have enabled them to escape intraguild predation by H. axyridis in this system.     

有益真绥螨与巴氏新小绥螨的集团内捕食和同类相残作用

【目的】有益真绥螨Euseius utilis是北方地区广泛分布的一种多食性植绥螨,而巴氏新小绥螨Neoseiulus barkeri目前在我国广泛应用于农业害虫的生物防治中。本研究旨在对巴氏新小绥螨在本地的应用进行风险评估及为与有益真绥螨的联合释放提供依据。【方法】本研究在室内通过一系列实验,比较了实验室饲养的巴氏新小绥螨和采自内蒙古农业大学校园的有益真绥螨的雌成螨对同种或异种未成熟螨的捕食量、存活时间及产卵量的差异,检测了有益真绥螨与巴氏新小绥螨两种植绥螨相互之间的攻击强度以及种内和种间的相互作用。【结果】两种植绥螨都难以刺吸同种或异种植绥螨的卵,而对同种或异种植绥螨幼螨的捕食量最大,其次是对若螨。在无共同食物的情况下,有益真绥螨雌成螨对同种植绥螨幼螨的攻击性比对异种植绥螨幼螨的攻击性强(BreslowDay检验:χ~2=13.84,df=1,P0.001),且有益真绥螨对同种植绥螨幼螨的捕食量(9.10±1.65头)高于对异种植绥螨幼螨的捕食量(5.31±1.43头)(T检验:t=5.487,P0.001),巴氏新小绥螨对异种植绥螨幼螨的捕食量(7.48±0.75头)高于对同种植绥螨幼螨的捕食量(4.75±0.58头)(T检验:t=9.110,P0.05)。【结论】有益真绥螨更倾向于捕食同种幼螨而发生同类相残;巴氏新小绥螨更倾向于捕食异种幼螨而发生集团内捕食。     

Preliminary life table of the spotted tortoise beetle,Aspidomorpha miliaris (Coleoptera: Chrysomelidae) in Sumatra

From December, 1981 to February, 1982, a population study of the spotted tortoise beetle, Aspidomorpha miliaris, feeding on a shrub-like morning glory, Ipomea carnea, was conducted in Padang, Sumatra with the construction of a life table.

1. Dissection of oothecae collected from the field after hatching clarified that the average egg mass size was 43.4 and hatching rate was 25.0%. Causes for egg mortality included: parasitism by a wasp, Tetrastichus sp. A(Europhidae) (49.8% of eggs laid), predation (12.8%), disappearance of egg masses (5.3%) and hatching failure (7.1%). An ant, Dolichoderus bituberculatus, visiting the extrafloral nectaries of the host plnts was responsible for predation and disappearance of the egg masses. The ants again attacked the larvae and pupae.
2. Larvae showed a gregarious habit for almost the entire larval period. Survival rates between two successive instars were low and constant, ranging from 70 to 90%, but only 1.3% of final (5th) instars become pupae (six individuals). Since the growth of host plants was extremely rapid, shortage of food was rare in larval stages. The sudden drop in numbers after 5th instar may be due to predation and/or dispersal of matured larvae from the host plants for pupation.
3. Pupae were attacked by three species of parasitic wasps:Tetrastichus sp. C, Pediobius elasmi (Eulophidae) and Cassidocida aspidomorphae (Tetracampidae). Among the six pupae, two were parasitized, one died of disease and two disappeared. Out of 4078 eggs laid, only one emerged to adult.

     

Parasitoid complex of the bird cherry ermine moth Yponomeuta evonymellus in Korea

The parasitoid complex of Yponomeuta evonymellus L. (Lepidoptera: Yponomeutidae), the bird cherry ermine moth (BCEM), was sought in South Korea with the goal of identifying its potential biological controls. Thirteen primary and two secondary parasitoids were found. Diadegma armillatum (Grav.), Herpestomus brunnicornis Grav. (Icheumonidae), and Zenillia dolosa (Meigen) (Tachinidae) were the most important parasitoids causing 3.5%, 7.1%, and 7.7% of the combined parasitism of the host larvae and pupae, respectively. The composition of parasitoid species was more diverse in larvae than in pupae; 10 species were reared from larvae, compared to six from pupae. The parasitoid complex contributed to the relatively low mortality levels of Yponomeuta evonymellus with the combined total rate of parasitism of 29.6% for the host larvae and pupae. This level is below that found in some European populations (50%) and is not greater than the larval rate of parasitism (31%) found in the congeneric apple ermine moth in Korea. This low rate of parasitism is partly attributed to the parasitism by Ageniaspis fuscicollis (1%) detected in Yponomeuta evonymellus, which is similar to that detected in Yponomeuta evonymellus in European reports. This is the first report of the parasitoid complex attacking the BCEM in Korea.     

Elevationally biased avian predation as a contributor to the spatial distribution of geometrid moth outbreaks in sub‐arctic mountain birch forest

1. Population dynamics and interactions that vary over a species' range are of particular importance in the context of latitudinal clines in biological diversity. Winter moth (Operophtera brumata) and autumnal moth (Epirrita autumnata) are two species of eruptive geometrids that vary widely in outbreak tendency over their range, which generally increases from south to north and with elevation. 2. The predation pressure on geometrid larvae and pupae over an elevational gradient was tested. The effects of background larval density and bird occupancy of monitoring nest boxes on predation rates were also tested. Predation on larvae was tested through exclusion treatments at 20 replicate stations over four elevations at one site, while pupae were set out to measure predation at two elevations at three sites. 3. Larval densities were reduced by bird predation at three lower elevations, but not at the highest elevation, and predation rates were 1.9 times higher at the lowest elevation than at the highest elevation. The rate of predation on larvae was not related to background larval density or nest box occupancy, although there were more eggs and chicks at the lowest elevation. There were no consistent differences in predation on pupae by elevation. 4. These results suggest that elevational variation in avian predation pressure on larvae may help to drive elevational differences in outbreak tendency, and that birds may play a more important role in geometrid population dynamics than the focus on invertebrate and soil predators of previous work would suggest.     

Effects of larval host plants on over-wintering preparedness and survival of the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Laboratory colonies of cotton bollworm larvae, Helicoverpa armigera, kept at 20 degrees C under a photoperiod of L:D=10:14 were fed on five host plants (cotton, corn, kidney bean, tobacco and tomato) and an artificial diet (control) to determine the effects of larval host quality on survival and pupal over-wintering preparedness. A separate experiment showed that diapausing pupae weighed more and contained greater nutrient stores than did non-diapausing pupae. Diapausing pupae reared on different host plants showed significant differences in terms of over-wintering reserve storage, and degree of cold-hardiness (extent of low-molecular-weight substances and SCPs), and survivorship. The more nutrients the host plant had, the more the pupae weighed and the higher the levels of total lipids and glycogen. Body water content was also significantly affected by larval food quality. The mean pupal super-cooling capacities varied significantly from -16.7 to -18.9 degrees C according to host plants the larvae feed on, and these significantly related to water content, pupal weight, lipid and glycogen content, and the levels of glycerol. Levels of trehalose, glycerol, and inositol, which were mainly low-molecular-weight substances, showed no significant differences among different host plants, except for trehalose. Pupal mortality varied from 39.7% on corn to 3.3% on the artificial diet, which was significantly related to pupal weight, total lipid content, trehalose levels, and super-cooling points. These results suggest that larval food quality can affect survival and influence the over-wintering preparedness of the cotton bollworm.     

Wood ants and a geometrid defoliator of birch: predation outweighs beneficial effects through the host plant

Soil amelioration by a wood-ant species and its consequences for the larval performance of autumnal moths feeding on mountain birch were studied at various distances from the nest mound. Soil nitrate and ammonium nitrogen did not show any clear relationship with distance. However, trees growing in the mound had over 20% more foliar nitrogen than more distant trees. When moth larvae were experimentally protected from predation, their survival rate and final weight tended to decrease with increasing distance. In a laboratory experiment with detached leaves, the relative growth rate of larvae was roughly 30% higher on leaves from trees located on the mound. Differences in larval performance refute the Plant Stress Hypothesis proposed by T.C.R. White and support P.W. Price's Plant Vigor Hypothesis. Predation by ants was examined along the same gradient in trees with and without a glue band that excluded ants from the canopy. Reduction in the daily survival rate of larvae attributable to ant predation was about 35% in trees growing in the mound and around 5% at a distance of 20 m. Other things being equal, about 25 times more larvae entering the penultimate instar would achieve the pupal stage outside the wood-ant territory than in the vicinity of the mound. While both the fertilizing and predatory influence of wood ants is clear, the domain of predation is much larger than the area where trees and their herbivores can exploit enhanced nutrient levels in and around ant mounds. The existence of undamaged green islands around ant mounds in otherwise totally defoliated mountain-birch forests cannot be explained by soil amelioration by wood ants but rather by their predatory activity. Received: 21 November 1996 / Accepted: 8 September 1997     

短时低温胁迫对广聚萤叶甲发育和生殖的影响

广聚萤叶甲Ophraella commnuna 是入侵性杂草豚草Ambrosia artemisiifolia的一种重要专一性天敌.为探明短时低温胁迫对广聚萤叶甲发育和生殖的影响,将广聚萤叶甲置于2,5,8,11和14°C人工气候箱内(RH 70%±5%,14L:10D)处理2 h,测定卵、幼虫、蛹存活率、发育历期及成...     

How predation by Podisus nigrispinus is influenced by developmental stage and density of its prey Alabama argillacea

The functional response of a predator to the density of its prey is affected by several factors, including the prey's developmental stage. This study evaluated the functional response of Podisus nigrispinus (Dallas) (Hemiptera: Heteroptera: Pentatomidae) females to fourth instars and pupae of Alabama argillacea (Hübner) (Lepidoptera: Noctuidae), an important pest of cotton (Gossypium hirsutum L., Malvaceae) in Brazil. The prey were exposed to the predator for 12 and 24 h, and in densities of 1, 6, 12, 18, 24, and 30 items per predator female. The predation data were subjected to polynomial regression logistic analysis to determine the type of functional response. Holling and Rogers' equations were used to estimate parameters such as attack rate and handling time. Podisus nigrispinus females showed functional response types II and III by preying on larvae and pupae, respectively. The attack rate and handling time did not differ between the 12 and 24 h exposure times. Predation rate was higher at higher larval and pupal densities; predation was highest at a density of 30 prey items per female, and it was similar at 18 and 24 prey per predator. Understanding the interaction of predators and their food resources helps to optimize biological control strategies. It also helps the decision‐making and the improvement of release techniques of P. nigrispinus in the field.     

Temperature-dependent post-diapause development and prediction of spring emergence of the pine needle gall midge (Dipt., Cecidomyiidae)

Abstract:  We determined the influence of temperature on post-diapause development of overwintered Thecodiplosis japonensis Uchida et Inouye (Dipt., Cecidomyiidae) under various treatments (12, 15, 18, 21, 24, 27 and 30°C) in an effort to predict its spring emergence. Survival and developmental period for the overwintered larvae and pupae were significantly influenced by temperature. Linear and nonlinear regression models quantitatively described temperature-dependent development and survival of T. japonensis . The survival models exhibited right-skewed bell shape patterns for all stages, indicating a more detrimental impact on survival at high temperatures. Theoretical optimum temperatures with highest survival were 22.3, 24.0 and 24.0°C for the overwintered larvae, pupae and total post-diapause development (the larvae to adults) respectively. Pupal mortality was higher at all temperatures than larval mortality and the suitable range of temperature for pupae was narrower than that of larvae. The nonlinear Briere model estimated that optimum temperatures with the fastest development were 29.1°C for larvae, 27.6°C for pupae and 27.0°C for larvae to adults. In a linear model, the lower threshold temperatures were 5.1, 7.1 and 5.9°C for larvae, pupae, and larvae to adults respectively. A predictive degree-day model was developed using trap catches of T. japonensis adult emergence during 1991–1995. The model accounted for 84.6% of year-to-year variation in adult emergence and predicted accurately the median emergence time in 1996.