A method for estimating natural survival rate and mean fecundity of an adult insect population by dissecting the female reproductive organs

Several problems were discussed in relation toMacDonald' s method (MacDonald , 1957) for estimating the survival rate of a natural population of adults with varying survival rates and unstable age structure.

1. Random samplings with a fixed sampling ratio and an appropriate census interval is pre-requisite during the occurrence of the adults.
2. At each sampling, female adults are dissected to know the ratio, p_i, of nulliparous females in ith sample (i=0, 1, 2, 3, …,). The Σn_ip_i/Σn_i gives an estimate of the ratio, Fα/F, of nulliparous females in the population where n_i refers to the population size on ith census date. If a constant daily survival rate is assumed, the daily survival rate is estimated from equation (4′). When the survival rate is not constant over the period of adult occurrence, e. g. before and after the initiation of oviposition, the survival rate during pre-ovipositional period is estimated by equation (4″).
3. Decision of an economic census interval to obtain a reliable estimate of the ratio, Fα/F, is depending on the form of emergence curve, particularly on its duration and the length of pre-ovipositional period. If the normal distribution can be assumed for the emergence curve, an interval less than one third of the emergence period is recommended. Concerning with insects having a long pre-ovipositional period, a census interval which exceeds one third of the emergence period still gives a good estimate of Fα/F.
4. The mean realized fecundity of some kind of insects can be estimated by equation (5′ or 5″) using the estimates obtained by the present method.

     

Population behaviour of the southern green stink bug,Nezara viridula,with special reference to the developmental stages of early-planted paddy

Population behaviour of adults and 5th-instar nymphs of Nezara viridula L. was analysed by means of the marking-and-recapture method in an early-planted paddy field. The field contained five varieties of rice which differend in growth states. It was estimated that a total of more, than 7,000 adults of the first generation, in which at least 3,000 were females, invaded the field from early July to middle August. Egg-mass census data, however, indicated that only 10 per cent or less of the females participated in egg-laying. This was largely due to the, low rate of adult survival. The adults preferred younger plants, for both feeding and oviposition. The method described byIwao et al. (1966) permitted estimate that 3,300–3,400 of the 5 th-instar nymphs and 1,100–1,200 of the adults of the second generation were produced from 298 egg-masses (25, 700 eggs); while 95–6 per cent of the individuals were thought to have died before reaching adulthood. Most of the 5 th-instar nymphs moved less than 4 m in three days as long as the condition of food plants remained suitable, but they tended to move more towards younger plants when those on which they lived became too mature. The apparent survival rate of the second generation adults was very low, probably due both to a rapid emigration and a high mortality of newly-emerged adults.     

A marking-and-recapture analysis of the adult population of a phytophagous lady-beetle,Epilachna sparsa orientalis

A marking-and-recapture study of a population of overwintered adults of Epilachna sparsa orientalis was carried out in a small farm containing potatoes and egg-plants. The experiment involved a single release and five recapture samplings during May–June. The data were analysed byLeslie's re-recapture method. Assumption of randomness of sampling proved to be well satisfied. Survival rate of the overwintered adult population was maintained as high as 90 per cent per week or more until early June, and then it declined rapidly towards the end of June. Initially overwintered adults exclusively lived on potato plants, but half of the population alive in mid June migrated to nearby egg-plants. Emigration out of the experimental field, however, seemed not to be occurring. Recapture data of marked individuals in the potato field indicate that majority of the individuals stayed within a radius of 3 m, at least for 2 weeks. Similar data taken from another field also suggest that their mobility was far restricted as compared with random movement within the field. Some comparisons were made between the population behaviours of overwintered adults of E. sparsa orientalis and E. vigintioctomaculata.     

Developmental status of endo-developmental stages of Microplitis rufiventris kok. in Spodoptera littoralis (boisd.) larvae topically treated by juvenile hormones I and II

The juvenile hormones I and II (JHI and JHII) were topically applied at concentrations of 1 or 5 μg to Spodoptera littoralis larvae containing newly deposited eggs of Microplitis rufiventris. The study demonstrated that both hormones do influence several aspects of the development of the parasitoid after treatment of its host larvae. Of these effects: (1) significant lengthening of periods of eggs and larvae, (2) moulting failure of parasitic larvae, (3) moulting the parasitic larvae into supernumerary instar, (4) arrest of postembryonic development in the first larval instar, (5) reduction in the emergence rate of parasitoid larvae, and (6) influence on embryogenesis. The application of JHI was more effective in disrupting the endo-development of the parasitoid than JHII. In all tests, control hosts produced significantly (P < 0.01) more parasitoids than treated ones. Off-target effects on natural enemies may seriously limit the use of JHs, especially in integrated control programmes.     

Studies on the population dynamics of a thistle-feeding lady beetle,Henosepilachna pustulosa (Kôno) in a cool temperature climax forest

1. A field study was carried out on the population dynamics of a thistle-feeding lady beetle, Henosepilachna pustulosa (Kôno ) living in a cool temperature climax forest in northern Kyoto Prefecture, central Japan.
2. Intensive marking, release and recapture program was carried out to estimate the adult population parameters by usingJolly-Seber method.
3. Sampling ratio was around 50%. Marking ratio rapidly rised as the census progressed and approached to 100%.
4. Sex ratio (% ♀) was 63–69% in both overwintered and new adults.
5. Daily survival rate was as high as 0.95 or more and constant throughout the season. Adult longevity in the spring was longer than 40 days.
6. Reproductive rate i. e., the ratio of the number of newly emerged adults in a given generation to that of overwintered adults in the preceding generation, is very small, ranging 1–3, whereas winter survival is higher than 50%, consequently the size of populations in the study area remain in a remarkably constant size and it never reached a level where intraspesific competition occurred.
7. The population characteristics of H. pustulosa are compared with those of the two closely related species, H. vigintioctopunctata and H. vigintioctomaculata, which are the pests of Solanaceous crops. Hp is more K-strategic than the two pest species.

     

Population regulation of a mosquitoArmigeres theobaldi with description of the animal fauna in zingiberaceous inflorescences

1. Inflorescences of some Curcuma and Zingiber (Zingiberaceae) in tropical Asia provide an unique aquatic habitat being discrete, small, and made of numerous smaller compartments (the bracts).
2. The aquatic community in inflorescences of Curcuma in northern Thailand was composed of immature Diptera, of which the biting midge Dasyhelea and the mosquito Armigeres theobaldi were the commonest. No important competitors, predators or pathogenic parasites for the mosquito were confirmed.
3. Inter-inflorescence distribution of the mosquito was contagious. Within each inflorescence, the fourth-instar larvae or pupae usually occupied bracts singly.
4. The k-value analysis detected density-dependent mortality due to contest competition in the mosquito larvae.
5. Variations in the larval and pupal mosquito size were density-independent and remarkably small as compared with size variations known for other mosquitoes.
6. These population attributes (large density-dependent mortality with density-independent, minimally variable individual size) appear unique among mosquitoes, arising from conspecific killing, efficient foraging (inter-bract movement by crawl and single occupation of bracts), and availability of host plant tissues as supplementary food.
7. A simple population model suggested that a small proportion of adult females lay eggs.

     

Effect of solar ultraviolet radiation on survival of krill larvae and copepods in Antarctic Ocean

The effect of solar ultraviolet radiation on the survival rate of Antarctic zooplankton was examined in February–March in 2002. We investigated survival rate of calyptopis larvae of Euphausia superba and late copepodite stages (IV and V) of large dominant calanoid species, Calanoides acutus and Calanus propinquus reared in quartz jars with three different radiation regimes (total radiation, exclusion of UVB, exclusion of UVA and UVB) and a dark control. The survival rates of the krill larvae decreased after 3 days from start of the experiment, being below 50% at 4 days in the treatments with total radiation and exclusion of UVB, although most individuals could survive until the end of the experiments in the treatments with exclusion of both UVA and UVB and dark control. The calanoid juveniles showed almost same pattern of survival curves as the krill larvae did, but survived slightly longer. Although >10% of surface UVA radiation at 340 and 380 nm penetrated down to 30 m, both C. acutus and C. propinquus were mostly distributed above 20 m. Surface swarm of the krill larvae can be often recognized in the previous studies. These results suggest that not only solar UVB but also UVA radiation potentially lower the survival rate of Antarctic zooplankton at depth less than 20 m.     

Population dynamics of the japanese clouded apolloParnassius glacialis butler (Lepidoptera: Papilionidae). I. changes in population size and related population parameters for three successive generations

1. Population dynamics of a univoltine butterfly Parnassius glacialis (Lepidoptera: Papilionidae) was studied with mark-recapture methods for three successive generations in a hilly region in Kanazawa City, Ishikawa Prefecture, Japan in 1981–1983.
2. Jolly (1965) andSeber's (1973) method was applied to the mark-recapture data to estimate population parameters (daily survival rate, longevity, population size, sex ratio, etc.).
3. Sampling ratios were at least 50% and 30% for males and females, respectively.
4. Mean daily survival rate for males ranged 0.81–0.86 and that for females 0.80–0.84. Mean longevity was about 4–7 days for the males and about 5 days for the females. Spiders killed more males than females. Maximum longevity for an individual recorded during the study was 31 days for males and 18 days for females.
5. Emergence of the butterflies was later and less synchronous in 1981 than in 1982 and 1983. This was thought to be due to later extinction of heavier snow in 1981 than in the other years.
6. The population remained relatively stable for the three successive generations, with estimated total numbers of 914, 1277, and 869.
7. Estimated sex ratio (% females) was 30–40% at emergence

     

Moulting and survival of <Emphasis Type="Italic">Amblyomma variegatum</Emphasis> (Acari: Ixodidae) nymphs in quasi-natural conditions in Burkina Faso; tick predators as an important limiting factor

The survival rate of Amblyomma variegatum engorged nymphs was studied in 9 cohorts released during the first part of the dry season (i.e. the nymph infestation period in the region) and placed on a natural savannah, either in plastic containers or in cages driven into the soil and open at the bottom. All nymphs put in the containers placed in the sun died rapidly, while a high moulting rate (94%) was observed in containers placed in the shade. This rate reached 63% for the ticks released in the cages. The moulting period lasted from less than 4 to more than 6 weeks, depending on the release period: unfed adults are therefore present in the pasture 4–5 months before the onset of the adult infestation period. The survival rate of the unfed adults did not vary according to the release period of the nymphs: at the beginning of the rainy season, 20–25% of the adult ticks were still alive in the cages. Very important variations in survival and disappearance rates were observed according to the place where the cages had been installed: within a few metres, the survival rate could vary from 0 to 90%, presumably because of the activity of predators which removed also dead tick from the plastic containers. Predators may then have a great but highly variable and unpredictable impact on the natural population of A. variegatum adults. Engorged nymphs released on pasture were able to find suitable micro-habitats allowing survival, covered up to 2.8 metres to reach them, and grouped together at the neck or root network of bushes and grass clumps, sometimes burrowing to a depth of 10 cm.     

Larval development of hermit crab Clibanarius longitarsus: Synergistic effect of heavy metals

The levels of heavy metals copper and zinc were found to be high in the Vellar estuary. Therefore their effects on the larval development of the abundant hermit crab Clibanarius longitarsus were studied individually and in combination from hatching till moulting to glaucothoe stage in the laboratory using freshly hatched Artemia nauplii as food. The 96 h LC50 values found with 100 larvae each kept in 10 different concentrations of copper and zinc (350, 300, 250, 200, 150, 100, 50, 25, 10 and 5 ppb) were 50 ppb for copper and 90 ppb for zinc. Based on these 96 h LC50 values, three sublethal concentrations were chosen for the metals copper and zinc at 50%, 25% and 10% levels of the LC50 values. With increase in concentration of the test medium, the survival rate decreased and the time required for the completion of each zoeal stage increased. Copper was found to be more toxic than zinc as the survival rate in copper concentrations was lower than those in zinc concentrations. The survival rate in the mixed concentrations of metals was lower than in individual concentrations.     

Effects of time-dependent intraspecific competition on offspring survival in the butterfly, Anthocharis scolymus (L.) (Lepidoptera: Pieridae)

Effects of mothers' eclosion and oviposition timing on the survival of their offspring in the pierid butterfly Anthocharis scolymus (L.) was examined. I recorded the performance of individual eggs and larvae that differed in their mother's eclosion and oviposition timing in a natural population, where A. scolymus feeds on Turritis glabra (L.) Bernh. Eggs laid early in the season, and larvae emerging from these eggs, had higher survival than eggs laid later, and larvae emerging from eggs that were laid later in the season, the causal factor being egg cannibalism by larvae on the same host plant. Logistic regression showed that females eclosing early in the season had higher offspring survival than females eclosing later. I conclude that optimal timing of adult eclosion in A. scolymus is a trade-off between eclosing early with associated higher offspring survival but lower egg-laying rate, and eclosing later with associated lower offspring survival but higher egg-laying rate. Received: 4 August 1997 / Accepted: 19 October 1997     

Prevalence of parasitism and adult survival time of Aedes albifasciatus (Diptera: Culicidae) parasitized by Strelkovimermis spiculatus (Nematoda: Mermithidae)

We described the carryover of Strelkovimermis spiculatus (Poinar and Camino) (Nematoda: Mermithidae) from mosquito larvae, the primary site of maturation, to adults. We analyzed the survival time of male and female Aedes albifasciatus (Macquart) (Diptera: Culicidae) parasitized by S. spiculatus, the time of emergence of nematodes from adult mosquitoes, and the state of parasitism in the same mosquito cohorts during the immature stages. Mosquito larvae with single and multiple parasitism (up to 11 parasites) were observed. The mortality of mosquito larvae and adults was produced in all cases where at least one mermithid emerged. The mortality of S. spiculatus showed an increasing trend in mosquito larvae with larger numbers of nematodes and was higher in larvae parasitized by eight or more nematodes. Maximum survival of parasitized adult females of Ae. albifasciatus was 38 days, while non‐parasitized adult males and females survived 39 and 41 days, respectively. Strelkovimermis spiculatus mortality was observed in Ae. albifasciatus larvae with single or multiple parasitisms. The spread of mermithid parasitism in adult mosquito populations is discussed.     

On a method for estimating the rate of population interchange between two areas

A method for estimating the rate of population interchange between two areas is described in this paper. It is applicable to the case where the sampling ratios and the survival factors of the populations on two areas are different from each other. From the marking-and-recapture data taken at three successive occasions, we can obtain the estimates of emigration factors, total survival factors over two areas and the ratio of surviving migrants to the total survivors over the two areas, for each of two populations initially living on different areas.     

Effects of temperature on survival, development, growth and feeding of larvae of Yellowtail clownfish Amphiprion clarkii (Pisces: Perciformes)

To understand the physiological and ecological responses of marine fishes to the change of water temperature, newly-hatched larvae of Yellowtail clownfish Amphiprion clarkii were reared in captivity at water temperatures of 23, 26 and 29 °C till they completed the metamorphosis to juvenile phase, and larval survival, development, growth and feeding were evaluated during the experimental period. The results showed that water temperature influenced the physiological performance of larvae of A. clarkii significantly. The survival and growth rates of larvae of A. clarkii increased significantly with the increase of water temperature from 23 to 29 °C (P < 0.05). Water temperature also influenced larval development of A. clarkii significantly and larvae reared at 23 °C took longer time for post-larval development and metamorphosis compared to 26 and 29 °C (P < 0.05). Total length and body weight for post-larval development and metamorphosis decreased with the increase of water temperature from 23 to 29 °C (P < 0.05). Q₁₀ in developmental rate was higher than in daily growth rate at the same rearing temperature, indicating that at water temperature had greater influence on larval development than on growth. Water temperature also influenced larval feeding of A. clarkii significantly with feed ration (FR) and feed conversion efficiency (FCE) increased with the increase of water temperature from 23 to 29 °C (P < 0.05). There was a positive correlation between FR and specific growth rate (SGR) (P < 0.05) but not between FCE and SGR (P > 0.05), indicating that FR influenced growth rate significantly in larvae of A. clarkii. This study demonstrated that the physiological responses of larvae of A. clarkii to the change of water temperature and confirmed that water temperature influenced larval survival, development, growth and feeding significantly. This study suggests that the decline of larval survival and growth rates, extension of pelagic larval duration and reduction of larval feeding at lower temperature have ecological impacts on larval dispersal and metamorphosis, juvenile settlement and population replenishment in A. clarkii in the wild.     

Amino acids in nectar enhance longevity of female Culex quinquefasciatus mosquitoes

Culex mosquitoes feed on a wide range of nectars consisting of mostly carbohydrates and amino acids, however, little is known about the utilization and effects of these different carbohydrates and their accompanying amino acids on longevity. Culex quinquefasciatus larvae were reared on low- and high-quantity food diets to produce adults that were nutritionally representative of wild-caught and laboratory-reared mosquitoes. Emerging adults reared on low- or high-quantity food diets as larvae were then provided Lantana camara nectar mimics containing mixtures of carbohydrates and amino acids to evaluate effects of nectar amino acids on longevity. Carbohydrates (with or without amino acids) were a critical component of the adult diet, and in their absence, adult mosquitoes died within 3-5 days. The nectar mimic that contained both carbohydrates and amino acids did not increase adult longevity of males originating from either poorly or well-fed larvae. However, females receiving adult diets containing both carbohydrates and amino acids lived 5% longer than females fed adult diets with only sugar.     

Drop off rhythm and survival periods of <Emphasis Type="Italic">Amblyomma lepidum</Emphasis> (Acari: Ixodidae) under field conditions

In this study, engorged Amblyomma lepidum ticks were found to drop off in two peaks, one in the morning and one in the evening. Most larvae and females engorged during the morning hours between 06.00 h and 10.00 h with a peak around 08.00 h, whereas the majority of the nymphs dropped in the evening between 18.00 h and 24.00 h with the peak around 22.00 h. Although the effect of time on drop-off patterns of the ticks was statistically significant (p≤ 0.001), there were no significant seasonal influences. Survival of unfed stages of A. lepidum was also studied and was found to increase from larvae to adult ticks. The longest survival periods of 10, 11 and 14 weeks were recorded during the wet season for larvae, nymphs and adults, respectively. It is concluded that environmental conditions required for survival of A. lepidum are optimal only during the wet season and that during other seasons the tick depends primarily on prevailing micro-climatic conditions for its survival.     

Larval survival of two species of forensically important blowflies (Diptera: Calliphoridae) after submergence in water

Survival of larvae of known ages after 2 to 6 h of submersion under water was assessed by observing pupation and adult emergence in the cases of two blowflies of forensic importance, Chrysomya megacephala (Fabricius) and Chrysomya rufifacies (Macquart). Lowest survival occurred among 10‐h‐old larvae, which could not tolerate more than 2 h of submergence. Even with such a small period of submergence success of survival was only 33%. There were no survivors when 20‐ and 30‐h‐old larvae were submerged for more than 3 and 4 h, respectively. In the cases of 40‐, 50‐, 60‐ and 70‐h‐old larvae there were no survivors if submergence was more than 5 h. The results show that there is an inverse relationship between submergence period and survival rate: the longer the submergence period, the lesser is the survival rate. This study provides data that are potentially useful in estimating the minimum time since submergence (TSS) of a corpse during forensic investigations.     

Population dynamics ofLuehdorfia japonica Leech (Lepidoptera: Papilionidae)

1. An adult population of a papilionid butterfly, Luehdorfia japonicaLeech , was studied by marking, release and recapture procedures in a hilly region in the suburbs of Kanazawa City, Japan.
2. Age of butterflies was estimated from the wing wear conditions, rated as winage categories 0 to 6.
3. Jolly (1965) andSeber's (1973) method was applied to the marking-recapture results for estimating the population parameters (sampling ratio, population size and survival rate).
4. Sampling ratio of males was consistently higher (around 50%) than that of females.
5. Newly emerged females were especially inactive, so that few of them were captured. From day 6.5 to day 10.0 they began to oviposit and became more active and more catchable.
6. An approximate sex ratio of 1∶1 was confirmed from the specimens collected in the field and by rearing experiments.
7. Daily survival rate was about 0.75–0.80 and mean longevity was about 4 days for both sexes. The maximum longevity observed was 17 days, for males and 21 days for females.
8. Dispersal by both sexes of the butterfly was more than 1 km.

     

Impact of Lantana camara hexane extract on survival,growth and development of Dysdercus koenigii Fabricius (Heteroptera: Pyrrhocoriedae)

Present research work investigated the impact of hexane extract of Lantana camara leaves on the survival, survival duration, growth and development of the Dysdercus koenigii. Newly emerged fifth instar nymphs were exposed to nine concentrations viz. 10%, 5%, 2.5%, 1.25% 0.1%, 0.05%, 0.025%, 0.0125% and 0.00625% of the extract by ‘dry film residual method’ for 24 h. The results indicated that the survival and the growth of the nymphs decreased with increasing concentrations of the L. camara extract. The nymphs presented developmental malformation including incomplete moulting followed by death of the moulting nymphs, supernumerary nymphal instars, adults with wing deformities, and adults with exuviae attached to the body. The GC–MS analysis of the extract indicated presence of phytoconstituents with insecticidal activities, and intermediates of the juvenile hormone biosynthetic pathway. It was surmised that these intermediates individually or synergistically influence JH biosynthesis. L. camara extract causes mortality, inhibits growth and development and results in developmental anomalies in the D. koenigii thus indicated its potentials in the ‘integrated pest management’.     

An experimental study on the foraging behavior of a pit-building antlion larva,Myrmeleon bore

Foraging behavior of a pit-building antlion larva, Myrmeleon boreTjeder was investigated experimentally to elucidate the relation between the feeding level and pit relocation.

1. In artificial sands constructed in the field the 3rd instar larvae of M. bore rarely changed the positions of their pits, though several antlions had moved actively until they constructed pits. The average feeding rate was 0.3 prey/day/pit, and about 60% of prey captured were ants.
2. To examine whether or not M. bore larvae concentrate into the area where they can capture more prey, 8 antlions were released into each of 6 boxes filled with sand. I divided the sand surface of each box into two half areas, then gave prey to the pits built in a half area and gave no prey to the pits built in the other half. During the 50-day observation period, nonfed antlions never moved into the area where prey were given.
3. The 3rd instar larvae were reared separately without food. Even under starved conditions they rarely relocated their pits until dealth. The average duration of survival period was 83.9 days.
4. The experimental results indicate that M. bore larvae adopt a tactic of sedentary ambushing. These larvae exhibit low movement rates which are independent of prey capture rates.