Studies on the distribution pattern of the pine needle gall midge,Thecodiplosis japonensisUchida etInouye (Diptera: Cecidomyiidae) in a pine forest

Summary Numerical changes and distribution patterns of the pine needle gall midge,Thecodiplosis japonensis Uchida etInouye, were studied during the period from 1978 to 1979 in a young plantation ofPinus thunbergii in Shiga Prefecture, Japan. The survivorship curve of this species was characterized by a low mortality of larvae in galls and two high mortalities before the formation of galls and during the overwintering period in soil. The within and between-trees distributions of eggs and larvae in galls were examined by using the regression method. The egg distribution per shoot was aggregative both within and between host plants. The within-tree variations in numbers of eggs per shoot were related to the differences in the abundance of available needles for oviposition per shoot among the canopy layers. The between-tree variations reflected the heterogeneous emergence of adult females in the study plot. The degree of aggregation increased from egg to gall stage in both within- and between-tree distributions and the increase was explained by the different mortality of larvae within trees and the inversely density-dependent mortality between trees. The distribution patterns in the soil habitat stages were examined by the patchness index ( ). This species showed aggregative distributions in soil stages. There was a correlation in spatial patterns of adult emergence between the successive generations. The distribution properties of this species were discussed in connection with the population dynamics and the availability of host plants in the study plot.     

Ecological studies on a dragonfly,Nannophya pygmaea ramber (Odonata: Libellulidae) I. seasonal changes of adult population and its distribution in a habitat

Summary Adult population of a dragonflyNannophya pygmaea Ramber inhabited in a damp ground was investigated with mark-and-recapture method in 1975. The following results about the seasonal changes of the population size and distribution in the habitat were obtained. Adults emerged from late May to mid August. The number of the adults was most abundant in early June, but that of matured males in early July. From the recapture data, the estimate of daily survival rate was 0.82, and the length of immature stage in males was estimated as 5 days or so. Total number of post-teneral adults emerged in the habitat was estimated as about 9,000. The mean crowding-mean density regression method was applied for the analysis of the distribution pattern of the adults. Matured males showed a spaced-out distribution, while females and immatured males distributed themselves rather aggregatively. Such a distribution pattern of the matured male would be attributed to their territorial behaviour. The territorial behaviour was considered to force the matured males to extend the distribution area in July when they were most abundant. From the above-mentioned results and some observations, the meaning of the territoriality in this species was discussed.     

Application of a marking-and-recapture method for the analysis of larval-adult populations of an insect,Nezara viridula (Hemiptera: Pentatomidae)

Summary Difficulty arises in applying marking-and-recapture methods to insects when the probability of recapture of marked individuals is changed with advancing age, either due to detachment of the mark by moulting (in the case of larvae) or to changes in their survival rate or their behaviour. A modification of the re-recapture method (Leslie et al., 1953) has been devised to analyze the capture-recapture data of the 5th-instar larvae and adults ofNezara viridula L. Estimation of the rate of moulting to the adult stage is made with the aid of additional information on larval survival. Migration rates of the larvae between the two halves of the census field is estimated byIwao's (1963) method. Through these analyses, the dynamic feature of the population during transition from the 5th instar to, adult is revealed. Several problems involved in the application of marking-and-recapture methods to insect populations are discussed. Contribution from the Entomological Laboratory, Kyoto University No. 392.     

Behavior and mortality of the southern stink bugNezara viridula in Hawaii

Summary This paper is concerned with some aspects of the ecology of the southern green stink bug,Nezara viridula, in Hawaii. Dispersal studies on adults showed an asymetrical dispersal pattern. The rate of plant to plant to movement by the adults was 3.3–6.7 feet per day. Mortality studies showed that egg predation by ants,Pheidole megancephala, was as high as 80–90 per cent. Egg parasitism byTelenomus basalis was highest during February, 1965, and adult parasitism byTrichopoda pennipes was highest during July, 1964, to January of the following year. The population ofN. viridula declined during May, 1964, to May, 1965. This decline occurred simultaneously with the decline in the number of eggs produced per female. It has been speculated that this reduction in egg production was caused by parasitism byT. pennipes. Published with the approval of the Director of the Hawaii Agricultural Experiment Station as Technical Paper No. 816. It is with great pleasure that I acknowledge with thanks the help that I received in various ways from the following: Dr. WallaceC. Mitchell, Dr. MervinKamran., Mr HarryKaya and Mr. HitoshiKamasaki.     

Effects of interspecific competition on development and reproduction in two giant water bugs,Diplonychus japonicus vuillefroy andDiplonychus major esaki (Hemiptera: Belostomatidae)

Summary We studied the interpecific competition between 2 species of predatory aquatic bugs,Diplonychus japonicus andD. major by conducting a field experiment. We set up 3 types of experimental plots in the paddy fields whereD. major predominated. The two plots contained single species of eitherD. japonicus orD. major, respectively, and one plot had both species in equal number. We compared the development and the reproductive performance between plots in each species. InD. japonicus, the number of eggs and early instar nymphs were significantly smaller in the plots containing both species than in the monospecific plots. However, the numbers of late instar nymphs and newly emerged adults were not significantly different between plots. The proportions of starved nymphs in both plots were larger than those in theD. japonicus's natural habitats. The final densities of adults in both plots were lower than those in the natural habitats. These results suggest that lower density ofD. japonicus in these paddy fields is due to the lack of available food for nymphs rather than the effects of interspecific competition withD. major. InD. major, significant differences were not found in the number of eggs, each instar nymphs and adults. These results suggest that the effects of interspecific competition did not affect the reproductive performance ofD. major.     

Anopheles subpictus Grassi: Observations on survivorship and population size using mark-release-recapture and dissection methods

Summary A mark-release-recapture experiment to estimate population survivorship and absolute size was performed with wild-caughtAn. subpictus adults at the village of Khano-Harni, Lahore District, Punjab Province, Pakistan during September 1978, the end of the monsoon rainy season, when temporal population abundance was maximized. Daily survival rate estimated from the recapture sequence of marked adults was low, males=0.192 and females=0.343. Survivorship for females estimated by several vertical age-grading procedures ranged from 0.347 to 0.628. Both stage- and age-specific life tables were calculated from vertical age-grading data determined by the dilatation method. Female and male population size was estimated byBailey’s modification of theLincoln Index and was found to average 4478.4 and 6106.8, respectively. The bionomics, survivorship and population size ofAn. subpictus in the Lahore are indicated that this species was probably not important in the transmission of human malaria.     

Process generating the ditribution pattern of eggs of the common cabbage butterfly,Pieris rapae crucivora

Summary The process generating the negative binomial in the distribution pattern of eggs of the common cabbage butterfly,Pieris rapae crucivora, was investigated by releasing the female adults in a net house where cabbages were planted. The distribution of butterflies visited and laid an egg or more per plant followed thePoisson series under the uniform light condition, while that of eggs laid per visit conformed to the logarithmic distribution. From these results, it may be concluded that the negative binomial arises from compounding of thePoisson and the logarithmic distribution. The observed frequency of eggs found per plant fitted to the negative binomial with parameter thus computed theoretically. The change in the degree of aggregation with the increase of the parental density was considered in connection with the above results. Aided by a grant from Scientific Research Expenditure of the Ministry of Education.     

Dynamics of buried seed population and seedling cohorts of two dominant weeds in a hill agroecosystem of the humid subtropics of India

Dynamics of the buried seeds and plant population of two dominant weeds, viz.,Emilia sonchifolia (Linn.) DC. andRichardsonia pilosa HBK were studied in the crop fields of Meghalaya, north-east India during radish and maize cropping and intervening fallow periods. The total buried seed population ofR. pilosa was always larger than that ofE. sonchifolia, but the germinable fraction was invariably greater in the latter. A major portion (39–41%) of the viable (germinable+dormant) seed population in both weeds was confined to the surface soil layer (0–5 cm). The viable seed population ofE. sonchifolia peaked during April, while that ofR. pilosa showed two peaks (during August and December). The survival pattern and half-lives of seedling cohorts showed, some differences in the two weed species, but both being summer annuals, their populations behaved in a similar manner by showing higher seedling recruitment (K) and survivorship (p) rates in the summer crop (maize) than in the winter crop (radish). However, the density of plants that could attain adulthood was significantly higher inE. sonchifolia thanR. pilosa which might have resulted in greater seed input of the former to the soil leading to its greater abundance in the crop fields. Supported by the University Grants Commission, New Delhi (Grants No. F. 3-37/87 SR II)     

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

Summary Population behaviour of adults and 5th-instar nymphs ofNezara 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.     

Comparative population studies of threePieris butterflies,P. rapae, P. melete andP. napi, living in the same area

Summary Utilization of patchy habitats by adult populations of threePieris butterflies,P. rapae, P. melete andP. napi was studied throughout the flight season in an area of their coexistence, about 3×1.5 km, in a farm village in the mountains in Inabu, Aichi Prefecture. Field study was by the mark-recapture method. Results were analyzed by dispersal distances and recapture duration decay curves for adults of different age-classes estimated on the basis of physical condition of their wings, together with supplementary information of daliy egg-laying rate of females, obtained in field cages. Sexually immature, mated femals ofP. rapae after teneral stage showed a migratory flight. On the other hand, reproductive females and all males ofP. rapae were strongly resident within suitable habitats, and reproductive females begun to lay eggs abundantly at sunny places of newly suitable areas within a short period.P. melete seemed to disperse gradually from emerged stites and females of this species continued to lay some constant numbers of eggs for more than ten days over a wider area.P. napi appeared more likeP. melete thanP. rapae. The habitats of the three species can be characterized as follows:P. rapae, temporary, continued for pre-reproductive females but localized for reproductive females and all males, and unstable;P. melete, permanent, widespread, and stable;P. napi, permanent, localized, and stable. The numbers of generations ofP. rapae, P. melete andP. napi were estimated to be about six, three and three, respectively. Seasonal fluctuations in the number of adults were influenced by the stability of their habitats, i. e., the population size fluctuated sharply inP. rapae, but it was much more stable inP. melete andP. napi. In view of these results, it can be said thatP. rapae fits the general characteristics of a r-strategist whereasP. melete andP. napi are more K-strategic thanP. rapae.     

A note on key factor analysis

Summary Various aspects of a model for key factor analysis (Manly, 1977a) are discussed. Equations for estimating the parameters of the model are given. The jackknife method is suggested for obtaining standard errors for estimators. The case of circular populations (where the adults in one generation produce all the individuals alive at the start of the next, generation) is considered. A computer program is described. Varley et al.’s (1973) data on the winter moth is used for illustrative purposes.     

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

Summary A marking-and-recapture study of a population of overwintered adults ofEpilachna 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 ofE. sparsa orientalis andE. vigintioctomaculata. Contribution from the Entomological Laboratory, Kyoto University, No. 371.     

An introduction experiment of an herbivorous lady beetle: Characteristics of the adult population

In May 1971, 45 adults of an herbivorous lady beetleEpilachna niponica (Coleoptera: Coccinellidae) from Asiu Experimental Forest were introduced into a botanical garden of Kyoto University, where is 10 km south of the southern limits of its distribution with being 3–5°C warmer than the original site. The introduced population of the lady beetle was thus investigated from 1975 to 1981. Mark-release-recapture experiments were applied to individual adult beetles, to estimate population size and daily survival rate. Overwintering adults emerged from hibernation around early April, reaching peak numbers in late April to early May, then gradually declined to late June. No adults remained at the end of June. Adult survival was maintained at a high level to early May, and declined consistently until late in the reproductive season. New adults began to emerge in late June and quickly reached a peak in early July; thereafter they decreased in number and had entered hibernation by late October. In spite of seasonally deteriorating food resources and heat stress in summer, new adults showed moderately high survival during the inimical period. New adults which emerged later in the season tended to be smaller in body size than those that emerged early. The proportion of females in the new adult population gradually increased throughout the pre-hibernating period, suggesting that male-biased mortality occurred during this period. When compared to the source population, the introduced population had a higher rate of population growth. Coupled with the improved population growth, heavy leaf damage during the larval period suggested that intensive intraspecific competition was most likely to occur among larvae in the introduced population.     

Phenological studies on the wing dimorphism of a semi-aquatic bug,Microvelia douglasi (Heteroptera: Veliidae)

Summary Seasonal changes in the percentage of macropterous individuals in natural population ofMicrovelia douglasi in permanent habitats were investigated in Shimane, western part of Japan. Macropterous forms of 5th instar nymphs occurred most frequently from late June to early July. However, the seasonal appearance of macropterous adults differed between habitats and years. There were significant effects of density, temperature, photoperiod and food availability on the percentage of macropters under laboratory conditions. The percentage of macropterous forms generally increased with density, but the mode of the response was modified by temperature, photoperiod and food availability. When insects were reared under long day photperiod (16L8D) with abundant food (0.5–1.0 g/container/day), the percentage of macroptery varied most among the different density treatments at the intermediate temperature (24°C) and the difference was reduced at higher temperature (28° and 32°C). Effects of temperature were small under the short day photoperiod (12L12D). Under 12L12D photoperiod sensitivity of density responses were higher at 32°C and lower at 24°C than those under 15L8D photoperiod. When the insects were supplied with food every other day, the density response became obscure. Ecological significance of environmental responses in the wing morph determination was discussed in relation to the heterogeneous environment of water surface.     

Biological control of Pacific mites and Willamette mites in San Joaquin Valley vineyards: part III. Role of tydeid mites

Summary In the absence of spider mites, tydeids (Pronematus anconai Baker andPronematus ubiquitus [Mc Gregor]) may serve as alternate prey to maintain good numbers of the predatory mite,Metaseiulus occidentalis (Nesbitt) (Acarina, Phytoseiidae), late in the season. This late-season predator and alternate prey relationship is necessary to stabilize Pacific mite populations and perpetuate balance in San Joaquin Valley vineyards. Thriving laboratory colonies of tydeids were reared on a diet of windblown pollens, including cattail pollen (Typha sp., Typhaceae) and bottlebrush pollen (Melaleuca sp., Myrtaceae).M. occidentalis was successfully reared on a diet of tydeids and ovipositing predator females were obtained. In addition, pollen dusted on grapevines significantly increased both tydeid and indirectlyM. occidentalis populations late in the season. These studies suggest that artificially disseminating cattail pollen or manipulating good pollen producing flora in and around vineyards may be used to correct situations where Pacific mites have become serious pests. This study was supported by grant No. GB-7322 toC. B. Hyffaker by the National Science Foundation.     

Humid microenvironment prerequisite for the survival and growth of nymphs of the rice brown planthopper,Nilaparvata lugens (St?l) (Homoptera: Delphacidae)

Nymphs ofNilaparvata lugens were experimentally reared from the 2nd instar in a cage covering part of the leaf sheath of an individual rice plant grown in a Wagner pot. Plants were covered with the cage from the water surface of the pot to 10 cm above the surface (lower cage-group) or from 10 cm to 20 cm above the surface (upper cage-group). Temperatures measured at three different parts of the cage remained fairly constant in both groups at around 25°C (23.7–25.2°C in mean value). In the lower cage-group, relative humidities measured at the three heights in the cage in (76.3–90.5% in mean value) markedly increased with the approach to the water surface. The nymphs of this group, particularly during the molting period, aggregated close to the surface. Eighty-two percent of the released nymphs emerged in this group. Relative humidities measured at three heights of the upper cage-group were 69.5–72.7% in mean value, and all the nymphs in this group died within 3 days after their release although half of them stayed on the rice plants within 6 h after their release. The role of relative humidity as a limiting factor on the range of the microhabitat and the population density ofN. lugens in rice fields was discussed on the basis of the results.     

Overwintering ecology of two social halictine bees,Lasioglossum duplex andL. problematicum

Summary Overwintering of two social halictine bees,Lasioglossum duplex (Dalla Torre) andL. problematicum (Blüthgen), was studied. InL. duplex many females stay near the old nests, each female preparing a hibernaculum separated from the natal nest. InL. problematicum most females overwinter communally within the natal nest. This difference in overwintering habits relates to the social structure in the next spring.L. duplex is nearly always solitary in spring although later becoming eusocial, whereas many nests ofL. problematicum are polygynous, beginning in early spring.L. duplex overwinters much deeper ( ) in the soil than doesL. problematicum ( ), but both species are safe from drops in soil temperature, which is above 0°C even in midwinter, and the bees' supercooling points are lower than −6°C. This cold resistance and the storage of sufficient food in the crop are reflected in the winter survival, which is much higher (79%) than the rate of successful nests in the spring active phase (25%). Bionomics of the eusocial halictine beeLasioglossum duplex VII. Contribution No. 2654 from the Inst. Low Temp. Sci.     

Population dynamics of houseflies,Musca domestica, on experimentally accumulated refuse

Summary The population dynamics of the housefly,Musca domestica, on patchy and unstable habitats consisting of refuse was investigated at a waste disposal site by using sticky flypaper and mark-release-recapture technique (Jolly-Seber's method). The newly disposed garbage was favorable for breeding of the flies for about one month after being disposed, while a mixture of garbage and ash from incinerated refuse was less favorable. On the garbage under favorable conditions, the rates of population increase was 1.25–2.82 per day, and approximately 1300–1500 flies were produced per square meter within the available period of one month. The rapid decrease in the fly density was observed just after the appearance of high density peaks. The mark-release-recapture study suggested that this rapid decrease would be mainly due to the density-dependent emigration of adult flies from the patchy habitats. The emigration was also activated when the time after garbage disposition became long.     

Population studies ofCavelerius saccharivorus Okajima (Heteroptera: Lygaeidae): A few findings on population interchange

Summary The change in population density ofCavelerius saccharivorus was studied in the sugar cane field and theMiscanthus habitats around it. This species spent 2 (or partly 3) generations a year. It was suggested that the density rose in the sugar cane field where the density had been low enough, when the population density increased in the nearby sugar cane fields. Likely, the density in theMiscanthus habitat increased with the density in the nearby sugar cane field. It seems that these are mainly due to flying movement of adults, and that the movement takes place in every season. It was found through the investigation in the sugar cane field that the percentage of long-winged adults increased with the population density. These adults seemed to emmigrate to the nearby sugar cane fields andMiscanthus habitats. The remarkable increase in the percentage of long-winged adults in the sugar cane field was probably due to the immigration into there. In theMiscanthus habitat the adult population was consisted mainly of long-winged ones. Through all the observations, it was suggested that the adult movement was associated with the population regulation and performed chiefly by long-winged adults.     

Elimination ofSitotroga cerealella (Olivier) bySitophilus zeamais Motschulsky from mixed laboratory cultures on maize

Summary This paper describes a series of experiments conducted to determine whySitophilus zeamais Mots. andSitotroga cerealella (Oliv.) could not survive together in maize cultures in the laboratory. The effect ofS. zeamais on different developmental stages ofS. cerealella was investigated. The presence of adultS. zeamais slightly affected moth copulation, egg laying and moth eggs in a mixed culture, but large numbers of developing moths inside maize grains were killed by the adult weevil through feeding on the grains. The major cause of elimination ofS. cerealella byS. zeamais from mixed cultures was therefore found to be damage to the immature moths in grain and such moth mortality increased as the developing moths became bigger in the grains. A weevil: grain ratio of approximately 1.4∶1 was found to be the critical weevil density at which the moth disappeared from the mixed cultures.