Enigmatic adult overwintering in damselflies: coexistence as weaker intraguild competitors due to niche separation in time

Odonata, like most freshwater invertebrates, tend to overwinter in water due to the thermal properties of a water environment. Winter damselflies (genus Sympecma), however, hibernate as adults in terrestrial habitats. The strategy of adult overwintering combined with high mortality is associated with several unique adaptations to semiarid conditions, but winter damselflies maintain this unique life history throughout almost the entire Palaearctic. We assume that the unique strategy of adult overwintering in temperate zones is indirectly maintained by niche separation in time. We used phenological data from the Czech Republic to compare the seasonal phenology of Sympecma spp. with other coexisting odonate species. Seasonal population growth patterns between S. fusca and other coexisting species representing different life histories were compared using GLMMs and LME. The models showed negative non-linear dependence between the population growth of S. fusca and the estimated abundance of compared species. We found that the specific strategy of adult overwintering makes it possible to avoid seasonal maxima of competition and predation in adult and larval stages. Adults may benefit from free niches during spring while larvae may benefit from size advantage among intraguild competitors and optimal conditions for development.     

谢氏宽漠王的生物学特性及行为

谢氏宽漠王Mantichorulasemenowi是荒漠半荒漠地区的有害昆虫之一。该文主要探讨了该虫的生物学特性和部分行为。该虫 2年发生 1代 ,世代不整齐 ,以成、幼虫越冬。卵期 1 0～ 1 8d ,幼虫共有 7龄 ,化蛹时间为 6月下旬至 8月上旬 ,蛹经过 1 1～ 1 7d羽化为成虫。食性杂。喜光 ,活动有明显的节律性。     

Activity patterns, diets and interspecific interactions of coexisting spring and autumn breeding carabids: Carabusyaconinus and Leptocarabus kumagaii (Coleoptera, Carabidae)

Abstract. 1. Activity patterns, diets and interspecific interactions of two coexisting carabid beetles, Carabus yaconinus B. and Leptocarabus kumagaii K. et K., were studied in a lowland habitat in Japan.
2. Larvae of C. yaconinus appeared from May to October and fed on earthworms. Those of L. kumagaii appeared from October to the next May and fed on dipteran and lepidopteran larvae.
3. In the adult stages, feeding habits and daily activities of the two species were similar. The beetles fed mainly on earthworms and other animal materials, but various plant materials were also utilized.
4. Direct competition for food items was observed both intra- and interspecifically. Interspecific interactions occurred only in early summer, however, because of the difference in breeding seasons (i.e. spring for C. yaconinus and autumn for L. kumagaii).
5. The difference in seasonal life history patterns between these carabids is a possible mechanism of coexistence.     

Geographic variability of the life cycle in Pterostichus melanarius (Coleoptera, Carabidae)

In Pterostichus melanarius, the seasonal dynamics of activity is characterized by two peaks (in mid-June-early July and in late July-mid-August). In southwestern Moldova, these peaks were registered twenty days later than in Moscow Province. In both regions, larvae and adults hibernate. Both hibernated immature adults and adults that had already bred before wintering start reproduction simultaneously. In hibernated immature individuals, the average number of eggs per female constituted 1.5 times that in the postgenerative females. In the steppe zone, the total number of eggs laid by immature females was closed to that laid by previously bred females, while in the southern taiga zone, hibernated immature females laid a greater number of eggs. In the steppe zone, females of a new generation lay a somewhat lower number of eggs in comparison with hibernated immature females, whereas the total number of laid eggs is significantly higher. In the southern taiga zone, both the average number of laid eggs and their total number are equal in females of a new generation and hibernated immature females. In Moldova, the majority of individuals of a new generation breed in the current season, whereas in Moscow Prov., about half the individuals hibernate without breeding. Over the largest part of the range, the life cycle of P. melanarius combines the one-year development with hibernating larvae with two-year development with the hibernating immature and postgenerative adults. The two subpopulation groups, wintering at different phases of the ontogenesis, are totally isolated at the northern border of the range. Within each subpopulation., individuals are characterized by the biennial life cycle; as a result, the polyvariant character of the life cycle turns into the monovariant one. We suggest that such a life cycle should be designated as the compensatory monovariant cycle, and populations, in which it is realized, as byside populations (from the English “side by side”).     

Enhancing conservation of the Tasmanian glow-worm, <Emphasis Type="Italic">Arachnocampa tasmaniensis</Emphasis> Ferguson (Diptera: Keroplatidae) by monitoring seasonal changes in light displays and life stages

The light displays by the Tasmanian Glow-worm, Arachnocampa tasmaniensis Ferguson (Diptera: Keroplatidae), in Exit and Mystery Creek caves in southeast Tasmania, Australia have been recognised as a world heritage value under the criterion relating to outstanding natural phenomena. To conserve and manage these populations, particularly in response to potential tourism development, a better understanding of their ecology is needed. Aspects of the life cycle of A. tasmaniensis were monitored over 24 months. A strong seasonal pattern was found, with pupae and adults most common in spring and summer. The increase in numbers of pupae and adults coincided with an increase in the number of prey caught in silk threads produced by the larvae. Larvae were present throughout the year but the number glowing varied both seasonally and spatially. In Mystery Creek Cave, the number of larvae glowing was generally highest during summer and autumn and lowest in winter and early spring. In Exit Cave, there was no consistent seasonal pattern in the number of larvae glowing among sites, and overall there was less variation between monthly counts than at Mystery Creek Cave. This difference in seasonal patterns between the two caves may be due to a difference in climate, with Mystery Creek Cave possibly experiencing a greater drying out of the cave air in winter than Exit Cave.     

The causes of seasonal changes in numbers of the yellow dung fly, Scathophaga stercoraria (Diptera: Scathophagidae)

ABSTRACT. 1. Counts of adult Scathophaga stercoraria (L.) on cow pats were made in Houghall, County Durham, in 1964 and 1965.
2. A spring peak of numbers was due to adults (overwintered mainly as pupae or larvae) maturing and going to dung to breed. Numbers then dropped, rising to one or more peaks in late June—early July. In 1964 there was then a summer drop in numbers until late September. In 1965 high numbers persisted in summer associated with cooler, wetter weather. Autumn peaks in both years persisted until severe frosts or snow.
3. Mature adults, developed from eggs laid during the spring peak, form the first generation when breeding in mid-late June. No clear generations can be identified after this, due to eggs being laid daily (females have successive gonotrophic cycles). Changes in adult numbers breeding reflects survival of eggs and newly-hatched larvae 5–6 weeks earlier, and lower survival rates of adults in mid-summer compared with spring and autumn.
4. Adult Scathophaga numbers in vegetation rose as numbers on dung dropped. Females dissected to count ovariole tunica dilatations showed that most flies in vegetation were immature, with some parous flies hunting insects to develop the next batch of eggs.
5. Females on dung were dissected and found to range from immature to seven-parous. Those gravid for the first time were grossly under-represented, possibly due to wider dispersal.
6. It is suggested that seasonal changes in this r-strategist cannot be explained simply in terms of generations nor by the occurrence of adult diapause.     

Seasonal patterns in abundance of water-beetles belonging to the Hydrophiloidea (Coleoptera)

Populations of Hydraena britteni Joy., Limnebius aluta Bedel (Hydraenidae), and Helophorus brevipalpis Bedel, H. strigifrons Thoms., Hydrobius fuscipes L. and Anacaena limbata Fabr. (Hydrophilidae) were studied from the break up of the ice until autumn or freezing at three different shores of a lake near Stockholm, Sweden. The beetles were generally found to frequent the zone immediately at the water's edge. Both larvae and imagines inhabit the uppermost 2 or 3 cm of the substrate. Two patterns in the seasonal abundance were found. (a) Maximal abundance during spring, minimal during summer, and sometimes a new, smaller maximum during late summer and autumn (Hydraena britteni, Helophorus strigifrons, Hydrobius fuscipes, Anacaena limbata, and perhaps Limnebius aluta). (b) An abrupt peak in abundance during July-August and very low abundance at other times (Helophorus brevipalpis). Type (a) is probably the general one in this region and type of habitat. It fits a univoltine life cycle, where the beetles breed during early summer and hibernate as adults. In other climates this life cycle seems to be modified, partial second generations may occur or development is retarded and a new generation does not emerge until next spring. Type (b) is shown by a univoltine species much disposed to flight. The peak coincides both with its dispersal phase and the emergence of the new generation. The species is thought not to belong to a closed, stable habitat but to ephemeral waters in open landscapes. Its ecology is quite different to that of H. strigifrons, which is considered to belong to more closed, stable habitats. Patterns similar to type (a) are also shown by Laccophilus spp. (Dytiscidae) and Haliplus spp. (Haliplidae) according to the literature. This may be an adaptation to the probable danger of being trapped in ice during winter. Like the water-beetles these two beetle groups also mostly leave the water margin during autumn. The pattern of type (a) of most Hydrophiloidea seems to be geared to the amounts of plant remnants in the littoral, imagines and some larvae being most abundant when the amounts are maximal, i.e. during spring. The plant material probably offers food and cover. It disintegrates rapidly during summer and a new maximum is reached next spring. The pond-like habitat, which may develop behind reeds is compared with ephemeral ponds. Both may be regarded as unstable habitats, each passing through a series of predictable changes. The difference is the final stage, often disastrous when a pond dries out, but seldom so in a lake when the water line moves outwards in the littoral during summer.     

Experimental simulations of climate change induced mismatch in oak and larval development rates impact indicators of fitness in a declining woodland moth

Consequences of climate change-driven shifts in the relative timing of spring activities of interacting species are insufficiently understood, especially for insects. We use a controlled experiment which simulates a trophic mismatch scenario in which lepidopteran larvae predominately feed on older leaves due to foliage developing faster than larvae growth rates. As a case study our experiment uses Orthosia cerasi, which is a widespread but declining woodland moth whose UK declines appear to be driven by warming temperatures. In the control experiment larvae are fed young oak Quercus robur leaves (bud burst stages six and seven), whilst in the treatment newly emerged larvae are fed young leaves but then gradually transition to feed on older leaves (post bud burst stage seven). We assess impacts on duration of the larval stage, pupal size and overwintering duration and survival. Larvae in the phenological mismatch treatment had a longer larval period, and smaller and lighter pupae. Larval diet did not carry over to influence emergence dates as earlier pupation of control larvae was balanced by an equivalent increase in the duration of the pupal stage. Increased time spent as larvae could increase predation rates from avian predators, whilst slowing the seasonal decline in food availability for those bird species. Reduced pupal size and weight are indicators of lower fecundity in emerging adults. Notably, we find that adults emerging from the mismatch treatment exhibited greater rates of abnormal vestigial wing development, which is likely to further reduce fitness. Trophic mismatches in which caterpillars have reduced availability of young leaves may thus contribute to the population declines observed in many woodland moth species due to increased mortality at larval stages, and adverse effects of early life conditions that reduce the reproductive success of emerging adults.     

Methods for estimating the demographic structure of the taiga tick (Ixodidae) based on results of standard parasitological observations

A retrospective estimation of the abundance dynamics of the taiga tick Ixodes persulcatus in mixed coniferous and leaf-bearing forests of the Udmurtia Republic in the period 1957-1986 was carried out. A possibility to estimate the absolute number of all stages of I. persulcatus based on relative indices. Females of I. persulcatus lay 20,250 eggs per 1 hectare, and this number of eggs gives birth to 15,000 larvae. From this number, 7870 larvae hibernate and 6550 individuals became fed. The number of nymphs is 5930, among which 5110 individuals live up to spring, and 1390 became fed. The number of adult mites in autumn is 1250; in subsequent spring this number decreases to 780. The mean number of engorged females is 8. The mortality rate of ticks caused by the deficit of hosts increases from preimaginal stages to adults; for larvae, nymphs and imago this index is 16.6, 72.8, and 97.9%, respectively. Quotas of individuals with 3-, 4- and 5-year life cycle among the unfed imago are 70.4, 28.0, and 1.6%, respectively.     

Asynchronous male and female life cycles in the sexually dimorphic, harem-forming isopod Paragnathia formica (Crustacea: Isopoda)

The complex life history of the sexually dimorphic, harem-forming isopod Paragnathia formica Hesse is described, combining published information with new observations. The results of a two-and-a-half year field study, carried out within the animal's saltmarsh habitat, are presented, revealing significant differences in the life cycles of males and females. Settlement to the breeding habitat of final stage male and female larvae, derived from the same annual generation, was recorded at very different times of the year. The total lifespan of males was shown to be twice that of females.
The larvae, temporary ectoparasites of estuarine fish, and the non-feeding, burrow-living adults are described and categorized into several developmental phases, whose numbers were recorded during the course of the study.
The annual production of larvae during a limited period in the autumn, and the subsequent settlement of final stage larval females and males the following year, were monitored. Larval females entered the burrows of adult males in the spring to breed, and died after releasing viviparous broods in the autumn. Larval males settled later in the summer, reaching adulthood in the autumn and overwintering before breeding some 18 months after their birth and dying at the end of the breeding season. Adult males thus bred with females from the next generation. The differences in male and female life cycles led to great seasonal variations in adult sex ratios, a huge winter bias towards males contrasting with a brief excess of females in the summer.     

Poly modal emergence of the tiger swallowtail, Papilio glaucus (Lepidoptera: Papilionidae): source of a false second generation in central New York State

Abstract. 1. The tiger swallowtail butterfly, Papilio glaucus (L.) (Lepidoptera: Papilionidae), is commonly assumed to have a bivoltine life cycle in central New York State and other parts of the northeastern United States. The seasonal abundance of adults in Tompkins County, New York, shows a bimodal pattern in some years, and a skewed unimodal pattern in others. We studied the incidence of diapause, the potential for successful development of two generations in the field, and the dates of adult emergence from overwintering pupae to determine whether these seasonal patterns are the result of bivoltinism.
2. Insects from Tompkins County, reared as larvae under 16L:8D photoperiod, uniformly enter pupal diapause.
3. Comparison of the heat units required for successful development of two generations with the heat units available in the field during 11 years shows that emergence of non-diapausing individuals would occur too late in the summer to contribute to the second peak of butterfly abundance. Offspring of non-diapausing individuals could only rarely complete development before the end of the growth season.
4. Diapausing offspring of butterflies collected in early June and late July differed sufficiently in dates of emergence to account for the field pattern of seasonal abundance.
5. Electrophoretic studies revealed no evidence of genetic isolation between early and late emerging butterflies.
6. These results suggest that polymodal emergence of diapausing insects can masquerade as a bivoltine life cycle.     

Seasonal selection and resource dynamics in a seasonally polyphenic butterfly

Seasonal polyphenisms are widespread in nature, yet the selective pressures responsible for their evolution remain poorly understood. Previous work has largely focussed either on the developmental regulation of seasonal polyphenisms or putative ‘top‐down’ selective pressures such as predation that may have acted to drive phenotypic divergence. Much less is known about the influence of seasonal variation in resource availability or seasonal selection on optimal resource allocation. We studied seasonal variation in resource availability, uptake and allocation in Araschnia levana L., a butterfly species that exhibits a striking seasonal colour polyphenism consisting of predominantly orange ‘spring form’ adults and black‐and‐white ‘summer form’ adults. ‘Spring form’ individuals develop as larvae in the late summer, enter a pupal diapause in the fall and emerge in the spring, whereas ‘summer form’ individuals develop directly during the summer months. We find evidence for seasonal declines in host plant quality, and we identify similar reductions in resource uptake in late summer, ‘spring form’ larvae. Further, we report shifts in the body composition of diapausing ‘spring form’ pupae consistent with a physiological cost to overwintering. However, these differences do not translate into detectable differences in adult body composition. Instead, we find minor seasonal differences in adult body composition consistent with augmented flight capacity in ‘summer form’ adults. In comparison, we find much stronger signatures of sex‐specific selection on patterns of resource uptake and allocation. Our results indicate that resource dynamics in A. levana are shaped by seasonal fluctuations in host plant nutrition, climatic conditions and intraspecific interactions.     

哈尔滨地区大猿叶虫发育历期与生物学特性

在哈尔滨对白菜上的大猿叶虫Colaphellus bowringi Baly的生活史和生物学习性进行观察研究。结果表明,大猿叶虫在哈尔滨地区绝大多数个体1年发生1代,少部分个体1年发生2代。主要以成虫入土在2～27cm土层中滞育越冬。越冬成虫翌年4月下旬开始出土活动。第1代发生在5上旬至7月上旬,第2代发生于6月中旬至7月中旬。所有成虫在7月下旬以后均滞育越冬。在25℃条件下,雌虫产卵期为6～55d,平均为30.95d,单雌平均产卵量为454.9粒。在25℃各虫态的发育历期为:卵(4.46±0.33)d,幼虫(8.22±0.26)d,蛹(4.17±0.22)d。各虫态发育起点温度卵为10.80℃,幼虫为10.95℃,蛹为9.79℃;有效积温卵为64.82日.度,幼虫为117.37日.度,蛹为64.36日.度。     

黑尾卷象的初步研究

黑尾卷象ApoderusnigroapicatusJekel近年来在山东荣成地区是危害刺槐的主要害虫。1年发生2代,以成虫于土中越冬。5～9月危害,10月上旬入土越冬。卵、幼虫、蛹在卷叶筒内生活;成虫食叶危害。本文报告了该虫的形态特征、年生活史、生活习性及天敌等,并提出了防治措施。     

Life history variation in a dobsonfly, Protohermes grandis (Megaloptera: Corydalidae): effects of prey availability and temperature

SUMMARY. 1. The life cycle of a predatory insect, Protohermes grandis (Megaloptera: Corydalidae), was compared in four streams in central Japan. The effects of annual temperature regime and prey availability on life history characteristics were also assessed.
2. The larval period was 2 years and small adults emerged in the Morito River, where summer water temperature was high and large prey scarce.
3. In the Nagura River, rich in large prey, the larval period was also 2 years in spite of slightly lower temperature, and the adult size was largest among the streams.
4. In Anado Fork with a low summer temperature, the larval development took 3 years, and large adults emerged. Large prey were abundant in this stream.
5. Seasonal abundance of large prey also affected the time large larvae left the stream to pupate. Larvae emigrated earlier in streams where the density of large prey sharply decreased after spring, than in streams where large prey were available throughout the year.     

Changes in structure and composition of an assemblage of Hydroporus species (Coleoptera: Dytiscidae) along a pH gradient

SUMMARY. 1. Patterns of total abundance and species relative abundances in an assemblage of predatory dytiscid beetles of the genus Hydroporus were examined along a pH gradient within a ditch in north-cast England.
2. During spring, total abundance of adult Hydroporus was greatest at the less acidic (pH 5.6–6.2) upstream sites, whereas total abundance of larval Hydroporus was greatest at the more acidic (pH 4.5) downstream sites. Both adults and larvae were more abundant in samples from the edge than from the middle of the ditch.
3. Species number and evenness did not differ along the pH gradient.
4. Species relative abundance patterns varied along the pH gradient, with particular species dominating at different sites. However, relative abundances of species changed discontinuously along the pH gradient.
5. Comparison of species abundance patterns along this pH gradient with published patterns of presence/absence among bodies of water with different pH revealed that species relationships with pH are often not consistent. Possible sources of this inconsistency are: geographic variation in species' pH preferences; complex responses of individual species to many factors in addition to pH; or random variation among sites due to colonization and extinction history.
6. The overall results suggest that pH is not the only, or even the most important, factor influencing Hydroporus populations and assemblage organization.     

Agroforestry management affects coffee pests contingent on season and developmental stage

1 Management of vegetational diversity in agroecosystems is a potentially regulating factor of pest population dynamics and may affect developmental stages in different ways.
2 We investigated the population dynamics of red spider mites, coffee leaf miners, and coffee berry borers in three management types of coffee agroforests: increasing plant diversity from a few shade tree species (simple-shade agroforests), intermediate-shade tree species (complex-shade agroforests) to high-shade tree species (abandoned coffee agroforests) in Ecuador. Furthermore, we studied how changes in agroforestry management affect population stage structure of each coffee pest.
3 Our results show that agroforestry management affected seasonal patterns of coffee pests in that higher densities of red spider mites were observed from August to December, coffee leaf miners from December to February, and coffee berry borers from May to July. Moreover, specific developmental stages of red spider mites, coffee leaf miners, and coffee berry borers differed in their responses to agroforestry management. During all stages, red spider mite reached higher densities in simple-shade agroforests compared with complex-shade and abandoned agroforests. Meanwhile, coffee leaf miner densities decreased from simple-shade to complex-shade and abandoned agroforests, but only for larvae, not pupae. Similarly, only coffee berry borer adults (but not eggs, larvae and pupae) demonstrated a response to agroforestry management. Environmental variables characterizing each agroforestry type proved to be important drivers of pest population densities in the field.
4 We emphasize the importance of considering seasonal differences and population structure while investigating arthropod responses to different habitat types because responses change with time and developmental stages.     

Worker honey bee ovary development: seasonal variation and the influence of larval and adult nutrition

We examined the effect of larval and adult nutrition on worker honey bee (Apis mellifera L.) ovary development. Workers were fed high or low-pollen diets as larvae, and high or low-protein diets as adults. Workers fed low-protein diets at both life stages had the lowest levels of ovary development, followed by those fed high-protein diets as larvae and low- quality diets as adults, and then those fed diets poor in protein as larvae but high as adults. Workers fed high-protein diets at both life stages had the highest levels of ovary development. The increases in ovary development due to improved dietary protein in the larval and adult life stages were additive. Adult diet also had an effect on body mass. The results demonstrate that both carry-over of larval reserves and nutrients acquired in the adult life stage are important to ovary development in worker honey bees. Carry-over from larval development, however, appears to be less important to adult fecundity than is adult nutrition. Seasonal trends in worker ovary development and mass were examined throughout the brood rearing season. Worker ovary development was lowest in spring, highest in mid-summer, and intermediate in fall.     

Biology and bionomics in Scotland of Anthocoris gallarum-ulmi

Abstract. 1. Observations were made on the biology of Anthocoris gallarumulmi De Geer (Hemiptera - Heteroptera: Anthocoridae) in West Central Scotland from 1973 until 1975. The life cycle was intimately linked with those of its principal prey species Schizoneura ulmi and S.patchae , leaf roll-gall aphids, and elm, their primary host ( Ulmus sp.).
2. Overwintered adults emerged in late April/May and could be found on a number of early flowering tree species, before congregating on elm in late May/June. This population was univoltine and exhibited obligatory female reproductive diapause.
3. Overwintered females emerged already mated but the subsequent pre-oviposition period was 25 days and oviposition period 27 days. Ova were deposited only in close association with galls of S.ulmi and Spatchae , and behavioural variations were shown between sites. Fecundity was c . 16 ova per female.
4. The incubation period was c . 8 days with the subsequent period of larval development 38–53 days, during which time the diet was almost exclusively either S.ulmi or S.patchae . Intergall migration was characteristic of post second instar larvae, which resulted in the concentration of fifth instar larvae and adults in a limited number of galls. It was during this period of local high population density that mating occurred.
5. Adults left elm within 14 days of imaginal ecdysis and thereafter, until overwintering, were recorded in only very low numbers from a range of tree, shrub and herb species.
6. Overwintering adults selected as hibernacula the bark of four tree species but principally Acer pseudoplatanus and Quercus robor . Females required a period of at least 75 days of cold 'shock' to terminate reproductive diapause.
7. Mortality among males surviving to spring emergence was 67%.     

Maladaptive photoperiodic response in an invasive alien insect, <Emphasis Type="Italic">Milionia basalis pryeri</Emphasis> (Lepidoptera: Geometridae), in southern Kyushu,Japan

The geometrid moth, Milionia basalis pryeri Druce, is an important pest of Podocarpaceae trees that has recently become established in the southern part of the main island of Kyushu, Japan. The species exhibits a multivoltine seasonal life cycle, with adults emerging mostly from spring to autumn, and occasionally being observed in winter. In this study, life-history traits and overwintering success were examined for a population collected in southern Kyushu. A long-day photoperiodic response was shown in larval and pupal development, with larvae and pupae developing significantly more slowly under short-day conditions than under long-day conditions. The critical photophases for this response were 12–13 h/day at 20 °C and 10–12 h/day at 25 °C. In the field, only individuals that pupated at a particular time in autumn remained in the pupal stage during winter, but all of them failed to eclose normally to adults, although some of them attained the wing pigmentation stage in winter to spring. This maladaptive seasonality in M. basalis pryeri in southern Kyushu is attributed to inconsistency between the climate of the new habitat and the innate ability of M. basalis pryeri to respond to seasonal cues, and is considered to be an ecological cost of a range-expanding insect.