Interaction between flight,reproductive development and oviposition in the pine weevil Hylobius abietis

• 1 The development of reproductive and flight capacity of pine weevils Hylobius abietis during the spring and their dispersal to, and subsequent development at, new clearfell oviposition sites comprise key phases in their life cycle in managed forests. At an old clearfell site where autumn‐emerging weevils had overwintered, weevils were trapped as they re‐emerged in the spring and tested for their ability to fly and then dissected to determine the degree of wing muscle and egg development.
• 2 Re‐emerging weevils were most abundant in pine growing at the edge of the clearfell and, over most of the trapping period (April to June), their capacity for flight (proportion flying and wing muscle width) was more advanced than in weevils from the clearfell itself, with a similar trend in the degree of reproductive development (proportion with mature eggs and egg volume).
• 3 In weevils from the clearfell, flight capacity and reproductive development increased concurrently to a peak around mid‐May. In weevils from pine, wing muscles were already well developed at the start of trapping, although few of them flew. Their more advanced development was attributed to the increased opportunities for maturation feeding after emergence in the previous autumn.
• 4 In the spring, weevils reached the canopy of trees for maturation feeding by walking and, to a lesser extent, by flight. Weevils dispersed by flight to oviposition sites in mid‐May when most of them were reproductively mature. After arrival, flight ability and wing muscle size declined rapidly but egg production was maintained until most weevils had stopped flying. When wing muscles reached their minimum size, there was a marked decline in egg size, suggesting that wing muscle breakdown is important in maintaining egg production at oviposition sites. Prospects for further wing muscle and reproductive development are discussed.

     

The ultrastructure of the flight muscle polymorphism in Cenocorixa bifida (Hung.) (Heteroptera,Corixidae)

Adult Cenocorixa bifida (Heteroptera: Corixidae) emerging early in the year in British Columbia are all able to fly. Insects emerging in the late autumn look similar externally, but are incapable of flight: the ultrastructure of their indirect flight muscles resembles that of immature tissue, indicating a block in the normal myogenetic sequence.     

Wing and flight muscle polymorphism in a lygaeid bug, Horvathiolus gibbicollis: determinants and life history consequences

ABSTRACT.

• 1 Horvathiolus gibbicollis (Costa), a ground-living seed-feeding bug of the mediterranean region, has two wing morphs. In macrop-terous bugs both pairs of wings are fully developed. In brachypterous ones forewings are reduced to about two-thirds and hindwings to less than a third of their length in macropters.
• 2 Each morph bred true with regard to wing length when reared under variable density, food and temperature conditions for several generations.
• 3 All F₁ offspring between crosses of the two morphs were brachypterous. In F₂ approximately 25% were macropters and 75% brachypters implying monogenic control of wingform.
• 4 Flight muscles in macropters vary from fully developed to totally reduced. This variation is determined by environmental conditions during adult life. Most young adult bugs have flight muscles, and totally starved or unmated bugs retain their flight muscles. Fed and mated females histolyse flight muscles as they start laying eggs, while most males of the same group retain their muscles.
• 5 Brachypterous bugs have a smaller thorax and larger abdomen than macropterous ones.
• 6 Brachypterous bugs reach adulthood slightly before macropterous ones, and they have a distinctly shorter adult preoviposition period.
• 7 Lifetime egg production does not differ significantly between the two wing morphs. However, the temporal pattern of egg laying is different in the two morphs. The m_x-curve of macropters starts later, then attains a higher peak and finally decreases faster than that of brachypters.
• 8 Initially, macropters lay smaller eggs than brachypters, but egg volume increases with age in macropters and eventually approaches that of brachypters.
• 9 The initial increase in reproductive effort (egg volumexegg number) of macropters is concomitant with wing muscle histolysis and the mobilization of thorax space for reproduction.
• 10 Adult survival rate does not differ between the morphs.

     

Reduced dispersal and survival in the sweet potato weevil (Euscepes postfasciatus) after irradiation

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Mutual benefit interactions between banded pine weevil Pissodes castaneus and blue‐stain fungus Leptographium serpens in maritime pine

• 1 Ecological interactions between banded pine weevil Pissodes castaneus and blue‐stain fungus Leptographium serpens, when simultaneously sharing the same host plant (maritime pine Pinus pinaster) in winter and spring, were investigated. Temporal components of the interaction were taken into account by either introducing the weevils and the pathogen simultaneously or sequentially, with the weevils being introduced 1 month after the fungal inoculation.
• 2 We measured larval mortality, development time, offspring number, sex ratio and body size of P. castaneus. Phloem phosphorus and nitrogen concentrations were also assessed. Furthermore, we tested whether: (i) emerging offspring transported propagules of the fungus; (ii) artificially‐contaminated weevils may transmit the disease to healthy trees; and (iii) field collected P. castaneus carry the fungus.
• 3 The fungus enhanced weevil colonization and brood production in both seasons. During winter and spring, adults from trees where the pathogen was inoculated prior to weevil introduction emerged earlier than weevils from trees where they had been introduced simultaneously with the fungus. During winter, weevils from pre‐inoculated trees were also larger. Sex ratio and larval mortality were not affected. Leptographium serpens did not affect phloem nitrogen content but phosphorus content was greater in plants inoculated with the pathogen, which may explain the findings on weevil growth.
• 4 Sixty‐five percent of the weevils that emerged from inoculated trees carried spores of L. serpens, although no successful isolation was made from field collected weevils. The fungus was recovered from 25% of the trees infested with artificially‐contaminated weevils.
• 5 These results suggest that P. castaneus benefits from the presence of L. serpens and may contribute to its spread.

     

Morphological variation associated with dispersal capacity in a tree‐killing bark beetle Dendroctonus ponderosae Hopkins

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Temptations of weevil: feeding and ovipositional behaviour of Hylobius warreni Wood on host and nonhost bark in laboratory bioassays

• 1 Warren root collar weevil Hylobius warreni Wood (Coleoptera: Curculionidae) is a long‐lived, flightless insect native to coniferous forests across northern North America. Girdling by larval feeding causes significant mortality on young trees. The insect poses considerable challenges to reforestation.
• 2 Adult weevils feed on all life stages of a variety of coniferous hosts prior to oviposition. Their relative feeding preferences, however, have not been quantified. Moreover, it is not known whether host bark influences oviposition behaviour.
• 3 Feeding preferences of adult weevils were tested in both choice and no‐choice laboratory bioassays using small branches from three conifers (lodgepole pine Pinus contorta var. latifolia, interior hybrid spruce Picea glauca×engelmannii, and Douglas‐fir Pseudotsuga menziesii) and one deciduous tree (trembling aspen Populus tremuloides). Measurements included the surface area of bark consumed, rate of consumption, the number of days of feeding, and, in the no‐choice assay, the number of eggs oviposited.
• 4 Bark consumption was greatest on pine and Douglas‐fir, followed by spruce. Little to no feeding occurred on aspen. Consumption did not vary between male versus female insects for any of the feeding metrics quantified.
• 5 The presence of aspen branches did not inhibit feeding on any of the other species in the choice bioassays.
• 6 The number of eggs laid by female insects did not differ significantly among tree species in the no‐choice assay. Eggs were laid indiscriminately in the presence of all four host types.
• 7 Results and opportunities for future research are discussed in the context of formulating new integrated pest management strategies for this insect, which is increasingly important in the period of reforestation subsequent to the mountain pine beetle epidemic in western Canada.

     

Flight endurance in relation to adult age in the green‐veined white butterfly Pieris napi

• 1 The flight apparatus in butterflies, as well as in other insects, is costly to manufacture. Since most animals live in a world where resources are limited, trade‐offs are expected and available resources must thus be allocated between flight and other functions, such as reproduction.
• 2 To mitigate this trade‐off, previous studies have shown that butterflies can break down flight muscles in the thorax as they age in order to use muscle nutrients for reproduction.
• 3 Although breakdown of flight muscles is expected to reduce flight ability, relative flight muscle mass (thorax mass/body mass) in many butterfly species does not decrease with age. The aim of the present study was to test the relationship between flight endurance and adult age in the green‐veined white butterfly Pieris napi (L.). The tests were performed in the laboratory at five different temperatures.
• 4 The results showed that age has a significant influence on butterfly flight endurance; older butterflies showed reduced flight endurance. Male butterflies fly for a longer time than females and flight endurance increases with temperature in both sexes.

     

稻水象甲(Lissorhoptrus oryzophilus Kuschel)的卵子发生-飞行共轭

１９９４～１９９６年对双季稻区稻水象甲发生消长和迁飞动态的系统研究表明,稻水象甲的飞行肌和卵巢发育随生活史的季节性变化出现兴衰交替,从而迁入迁出稻田和越冬场所,表现出典型的卵子发生－飞行共轭：春季越冬代成虫从越冬场所迁入早稻田后飞行肌消解而卵巢发育,繁殖形成一代致害种群。夏季一代成虫生殖滞育,飞行肌和脂肪体发达,绝大部分个体迁出早稻田行夏蛰并越冬;少量落入秧田者和早稻收割时散落田内而晚稻插秧时尚未迁离的个体卵巢恢复发育,飞行肌消解而构成二代虫源。秋季二代成虫羽化后生殖滞育,迁飞上山越冬;１０月中旬后羽化的个体卵巢和飞行肌均不再发育而滞留田内外越冬。取食高质量食料时,一代夏蛰成虫飞行肌再生,新羽一代成虫则首先发育飞行肌,而后解除生殖滞育。     

长颚斗蟋长翅和短翅型雌成虫飞行肌发育、生殖力及寿命的比较

为探讨长颚斗蟋Velarifictorus asperses (Walker)翅型分化的生态学意义, 对室内饲养获得的长翅和短翅型雌成虫飞行肌和卵巢的发育, 以及长、 短翅型雌成虫的生殖力和寿命进行了比较研究。结果表明： 羽化当日, 长翅型雌成虫飞行肌重38.68±9.15 mg, 显著高于短翅型的17.53±4.44 mg （P<0.05）; 而二者卵巢重量无显著差异（P>0.05）, 分别为4.69±1.04 mg和4.88±0.97 mg。羽化后8 d内, 长翅型雌成虫飞行肌重量增加了48.9%, 短翅型雌成虫飞行肌重量无明显增加; 而短翅型雌成虫卵巢的重量增加至93.5±11.7 mg, 约为长翅型雌成虫的4.5倍。短翅型雌成虫的产卵前期显著短于长翅型, 其早期产卵量及总产卵量亦显著高于长翅型; 而两翅型雌成虫中后期产卵量及寿命无显著差异（P>0.05）。此外, 长翅型雌成虫在羽化后12 d开始发生飞行肌的降解, 飞行肌降解个体的卵巢重量显著高于未降解个体, 与短翅型相似。结果提示, 飞行肌与生殖系统的发育之间存在资源分配的权衡关系（trade-off), 且这种资源分配的差异可能会导致长翅型与短翅型个体在生活史策略上出现分化, 即长翅型个体具有飞行能力, 而短翅型个体则在生殖方面获得更高的收益, 且飞行肌的降解可能是长翅型个体由飞行转向生殖发育的生理信号。     

Trade‐off between flight capability and reproduction in male Velarifictorus asperses crickets

1. There are numerous data that support the trade‐off between flight capability and reproduction in female wing polymorphic insects, but the relationship between wing form and fitness remains poorly investigated in males. 2. In the present study, the development of flight muscle and gonads, spermatophore size, and multiple copulation ability were investigated in both long‐winged (LW) and short‐winged (SW) males to verify this trade‐off, using a wing dimorphic cricket species Velarifictorus aspersus (Walker). 3. The LW males had better‐developed wing muscles than the SW males on the day of emergence, and both of them developed wing muscles after emergence, but the peak of weight in SW males was achieved 4 days later than that of the LW males. The accessory glands (AG) of the LW males developed significantly slower than that of the SW males. These results suggest that development and maintenance of flight muscles have a cost on the development of reproductive organs in male V. asperses. 4. The SW males produced significantly heavier spermatophores in a single copulation and mated more often than LW males. This indicates the SW males have a higher mating success than the LW males, thereby increasing their chance of siring offspring.     

Seasonal changes in the flight apparatus of winged females and sexual males of the aphid <Emphasis Type="Italic">Tuberculatus quercicola</Emphasis> (Hemiptera: Aphididae)

Tuberculatus quercicola (Matsumura) feeds on Quercus dentata Thunberg, and has mutualistic interactions with ants. Tuberculatus quercicola has two winged morphs in its life cycle, winged females appear in summer and sexual males appear in autumn. Previous studies have shown that wing loading (ratio of body volume to wing area) is higher for the winged females, because of ant attendance, resulting in extremely low dispersal. It is known that the nutritional quality of host plants is high in spring and autumn, when leaves are growing or senescent, and low in summer when leaves are mature. This study examined the effects of seasonal plant deterioration on the development of flight apparatus (wing size and flight muscle) of winged females and males. Moreover, field intercept traps were used to examine the extent of dispersal of males. The results showed that seasonal plant deterioration affected development of the flight apparatus of winged females, particularly flight muscle. Flight muscle development was significantly higher in winged males in autumn than in winged females. However, winged males were not caught in any of the traps. The different resource allocation to the flight apparatus of winged females and males is discussed.     

Evidence for Partial Migration in the Southern Monarch Butterfly,Danaus erippus,in Bolivia and Argentina

Migration is a common life‐history strategy that includes traits such as directed flight, increased wing size, seasonal lipid deposition and reproductive arrest. The degree of investment in these traits ultimately determines the life‐history strategy of individuals. Partial migration is a common mixed life‐history strategy where species or populations consist of both migrant and resident individuals. While this phenomenon is widespread across taxa, the ecological factors that select for and maintain partial migration are poorly understood, especially among insects. Here, we investigate regional life‐history traits associated with migration in the southern monarch, Danaus erippus, and describe a mixed life‐history strategy in this butterfly. Individuals from the Bolivian lowlands were observed throughout the year exhibiting mate‐ and milkweed‐directed behaviors. These butterflies had smaller wings, lower wing loads and maintained constant lipid and egg loads across summer and autumn months. Danaus erippus in the highlands of the Bolivian Andes were observed only in the summer and autumn months, during which they also showed mate‐ and milkweed‐directed behaviors. These individuals possessed similar‐sized wings and maintained similar lipid and egg loads as the lowland butterflies. In contrast, individuals from northwest Argentina showed persistent, directed, southwesterly flight during the autumn (March–May), larger wing size, higher wing loads, and increased autumn lipid deposition along with decreased egg production. These data indicate that D. erippus utilizes a mixed life‐history strategy with a combination of residents and migrants in the Bolivian lowlands, elevational migrants in the Bolivian Andes, and latitudinal migrants in northwestern Argentina.     

Factors associated with winged forms of soybean aphid and an examination of North American spatial dynamics of this species in the context of migratory behaviour

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Physiological trade‐offs between flight muscle and reproductive development in the wing‐dimorphic cricket Velarifictorus ornatus

Morphology, flight muscles, and reproductive development were compared between long‐winged (LW) and short‐winged (SW) morphs of the cricket Velarifictorus ornatus (Shiraki) (Orthoptera: Gryllidae). There was no difference in body weight and pre‐oviposition between the two morphs, but LW individuals had better‐developed flight muscles than SW individuals during and after emergence of the adult. The flight muscles at adult emergence represented 11.9% of the total body weight in the LW female and 4.9% in the SW female. In addition, the weight of the flight muscle of LW females increased by 50% during the first 5 days, whereas the flight muscle of the SW variant increased only slightly after adult emergence. The process of oviposition in LW, SW, and de‐alated females varied: SW females produced more eggs at the early stage than LW females, but de‐alation could shorten the time until the peak of egg laying and caused histolysis of flight muscles of LW females. There was no significant difference in total egg production between the above three groups. In the male, unlike the female, the accessory glands of the two wing morphs enlarged continuously at the same rate. There was no difference between the two wing morphs in the mass of the testes during the first 7 days after adult emergence.     

Oviposition and feeding behaviour by the vine weevil Otiorhynchus sulcatus on red raspberry: effects of cultivars and plant nutritional status

• 1 The vine weevil Otiorhynchus sulcatus is a major pest of horticultural crops worldwide, with root‐feeding larvae causing most damage. Adult oviposition aboveground may therefore influence levels of damage as the larvae are relatively immobile after oviposition.
• 2 The present study investigated feeding and oviposition behaviour on red raspberry Rubus idaeus using intact plants, ensuring that choices reflected the realistic differences in cultivar appearance and chemical composition. Previous studies investigating vine weevil feeding and oviposition on other crops have used excised plant material, which may inadvertently influence behaviour.
• 3 Adult weevils significantly preferred to feed on particular cultivars in the choice experiment (e.g. Tulameen), although they consumed significantly more foliage (0.22–1.03 cm²/day) on different raspberry cultivars (e.g. Glen Moy, Glen Rosa and a wild accession) in no‐choice situations.
• 4 In choice experiments, weevils tended to avoid laying eggs on some cultivars (e.g. Glen Moy and the wild accession). The number of eggs laid (1.91–4.32 eggs per day) did not, however, differ significantly between the cultivars in a no‐choice situation. Foliar nitrogen and magnesium concentrations were positively, although weakly, correlated with the total number of eggs laid.
• 5 The present study highlights the importance of considering both choice and no‐choice tests when assessing crop susceptibility to attack because weevils may avoid feeding on certain cultivars (e.g. Glen Moy) when given a choice, although this would cause significant damage to such cultivars if they were grown in monoculture (i.e. when there is no alternative).

     

Biology of Centistes delusorius, a parasitoid of adult apple blossom weevil

Abstract

• 1 Natural control of apple blossom weevil, Anthonomus pomorum (L.), deserves attention, as the pest is regaining importance with the declining use of non‐selective pesticides in apple and pear orchards. In this study the biology of Centistes delusorius (Förster), a specific parasitoid of adult apple blossom weevil, is investigated.
• 2 The parasitoid hibernates as young larva in an adult weevil, and juvenile development is resumed in early spring. The fully grown parasitoid larvae leave their hosts during full bloom at the end of April and early May, to pupate. The adults emerging in May oviposit into the newly emerged weevils, which initially feed on apple leaves.
• 3 Centistes delusorius was detected in six out of 15 host‐weevil infested orchards, but was only common in two with larger apple trees standing in grass. There, parasitism levels of around 30% were usual in hosts taken from treebands in winter.
• 4 The delicate larva is vulnerable, and the thin cocoon provides little protection against either desiccation or drowning on a weedless orchard floor. Observations indicate that successful pupation of C. delusorius demands stable humid conditions and some shelter, such as that found in grass or woodland soils.
• 5 Parasitoid females, provided with honey, lived for a mean of 6.3 ± 2.1 days under outdoor conditions in June. Their life span was similar whether they had access to and oviposited in hosts, or not. The species is pro‐ovigenic, and potential fecundity is about 40 eggs. Oviposition usually takes a few seconds. Parasitized female hosts do not reproduce.
• 6 Up to 95% of the parasitoid eggs laid in May develop into a second generation, the adults of which appear in July, when the host has entered aestivation. Older (British) records of C. delusorius outside orchards suggest that some parasitized hosts, like the healthy ones, leave the orchard prior to aestivo‐hibernation, so that the latter do not escape parasitoid attack in July.
• 7 A trapping sample in late June, when most non‐parasitized weevils have gone into aestivo‐hibernation, is probably the most efficient method to detect parasitized weevils.
• 8 The (near‐)absence of C. delusorius in many orchards is probably due not only to pesticide side‐effects, or scarcity of its host, but also to the absence of suitable pupation sites for the wasp.

     

Population dynamics and seasonal variation in the embryonic dormancy of Pilophorus gallicus (Hemiptera: Miridae): ‘don't put all your eggs in one basket'

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Seasonal flight patterns of Ips typographus in southern Sweden and thermal sums required for emergence

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The effect of temperature on the development and life cycle regulation of the pine weevil Hylobius abietis and the potential impacts of climate change

• 1 The pine weevil Hylobius abietis is widely distributed in the Palaearctic region where it is a major pest. Although predominantly semi‐voltine, with a 2‐year life cycle, the generation time across its range can vary from 1 to 4 years. The duration of the life cycle and the seasonal timing of weevil activity affect the economic impact and management of this pest, all of which are likely to change in a warming climate.
• 2 To determine the effect of temperature and tree species on weevil growth and development, laboratory experiments were performed with eggs, larvae, prepupae, pupae and adults, using, as appropriate, the host species Scots pine Pinus sylvestris L. and Sitka spruce Picea sitchensis (Bong.) Carr. under constant or alternating temperatures.
• 3 The development rate was linearly related to temperature, with developmental thresholds for eggs, larvae and pupae of 8, 4.5 and 7.3 °C, respectively. Day‐degrees were estimated for each life stage. Larval development was affected by tree species, being slower on Sitka spruce than on Scots pine, and was faster under alternating than constant temperatures.
• 4 The development time for prepupae was highly variable, with an apparent facultative prepupal diapause initiated by temperature. The temperature range 20–17.5 °C marked the transition between median prepupal development times of approximately 25 and 90 days. The prepupal stage may serve to minimize the risk of overwintering mortality in the pupal stage and help to synchronize the life cycle.
• 5 Larval and adult mass was positively related to developmental temperature, demonstrating an inverse temperature size rule, and weevils were heavier when developing on Scots pine than Sitka spruce. Development in alternating temperatures reduced weevil mass on Scots pine. The influence of temperature on weevil mass is likely to have a positive effect on fecundity and overwintering survival. The effects of climate change on development, voltinism and weevil mass are discussed.