THE EFFECTS OF METHODS OF SEWAGE APPLICATION ON THE ECOLOGY OF BACTERIA BEDS

Two difficulties in treating sewage in bacteria beds—namely, the choking of the beds by excessive growths of micro-organisms and the nuisance from flies breeding in the beds—are considered as one ecological problem. The effect of the manner in which the sewage is applied to the bed through different types of distributor nozzle on the film and fauna populations was studied. It was found that nozzles which provided a strong flushing action on the surface did not prevent excessive growth of film below the surface but did limit the grazing fauna, as a result of which the amount of film was greater than under jets in which the flushing action was reduced. Where this reduction was effected by allowing the sewage jet to first impinge on a splash plate, uniform conditions were produced in the medium below, where the species were in direct competition for food in the one ecological niche. As a result the fly larvae ( Anisopus fenestralis and Psychoda sp.) suppressed the population of Achorutes subviaticus (Collembola) during the winter. Where the flushing action was reduced by allowing the sewage to flow through an increased number of holes of smaller bore, two niches were provided, one wet region, subject to some flow of sewage, and the other drier region between the jets. Under this method, two populations existed side by side, Achorutes being present throughout the year in the drier zone and A. fenestralis larvae occupying the sub-jet zones.     

THE ECOLOGY OF ANISOPUS FENESTRALIS SCOP. (DIPTERA) IN SEWAGE BACTERIA BEDS

The assessment of populations of Anisopus fenestrate (Scopoli, 1763) in sewage bacteria beds by the trapping of adults at the surface has been previously proved to be unsatisfactory. Methods were therefore developed for determining the numbers of egg masses, larvae and pupae as well as the total organic matter in a unit volume of bed. The relative larval populations of three areas under investigation were related to the loading of the beds as measured by the sewage strength and rate of application. In the upper 2 ft. 6 in. the numbers of larvae and pupae per unit volume of bed decreased with depth. There was no evidence of any vertical migration of the larvae before pupation. The horizontal distribution of larvae was found to be affected by the method of distribution. In beds served with fixed spray jets larvae are more abundant nearer the jets than at some distance away. In beds served with travelling distributors the larvae are more abundant in the zones below the jets than in the drier intermediate zones. In both cases relatively higher percentages of pupae in the drier zones might indicate a horizontal migration of larvae before pupating or of the pupae themselves.
The incidence of the larvae throughout 1949 in all three beds showed recurring peaks. In the following year a more intensive investigation on one area showed that this was due to successive generations of the fly; the proximity of the peaks is determined mostly by temperature and their size by the amount of food available in the bed during the larval grazing phase.
In the area not treated with insecticide intraspecific competition during a period when food was limiting, due to depletion by the previous generation, resulted in a natural reduction in the population. In the area treated with insecticide the food was retained and this natural control was thereby delayed.     

The influence of host fruit and temperature on the body size of adult Ceratitis capitata (Diptera: Tephritidae) under laboratory and field conditions

The adult body size of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), varies in natural conditions. Body size is an important fitness indicator in the Mediterranean fruit fly; larger individuals are more competitive at mating and have a greater dispersion capacity and fertility. Both temperature during larval development and host fruit quality have been cited as possible causes for this variation. We studied the influence of host fruit and temperature during larval development on adult body size (wing area) in the laboratory, and determined body size variation in field populations of the Mediterannean fruit fly in eastern Spain. Field flies measured had two origins: 1) flies periodically collected throughout the year in field traps from 32 citrus groves, during the period 2003-2007; and 2) flies evolved from different fruit species collected between June and December in 2003 and 2004. In the lab, wing area of male and female adults varied significantly with temperature during larval development, being larger at the lowest temperature. Adult size also was significantly different depending on the host fruit in which larvae developed. The size of the flies captured at the field, either from traps or from fruits, varied seasonally showing a gradual pattern of change along the year. The largest individuals were obtained during winter and early spring and the smallest during late summer. In field conditions, the size of the adult Mediterannean fruit fly seems apparently more related with air temperature than with host fruit. The implications of this adult size pattern on the biology of C. capitata and on the application of the sterile insect technique are discussed.     

Seasonal changes in characteristics of cattle dung as a resource for an insect in southwestern Australia

The value of cattle dung as a food resource for the bush fly Musca vetustissima (Walker) in the winter rainfall agricultural region of southwestern Australia was assessed by bioassay in the laboratory. The size (headwidth) of adult females was measured from flies reared on different samples of dung. Variation in size correlated with seasonal patterns of pasture growth, larger flies being produced during the growing season from autumn to spring. Size declined with senescence of annual pastures in late spring and early summer, occurring later in southern areas where the growing season was longer. After pasture senescence, dung from shorter growing season areas usually produced larger flies, apparently a result of the inverse relationship between digestibility of feed and length of growing season. Dung from irrigated perennial pastures never produced flies as large as that from annual pastures but generally high values were sustained during summer. Grazing of cereal stubble and feeding of hay in annual pasture areas during summer usually caused some increase in fly size. A spontaneous resurgence in the size of flies often occurred several weeks after pasture senescence and was attributed to more thorough digestion as a result of reduced intake of less palatable dry pasture.     

Summer decline in populations of the yellow dung fly: diapause or quiescence?

Abstract. Yellow dung fly ( Scathophaga stercoraria (L.)) populations on cow pastures in Central Europe usually show a characteristic summer decline in fly numbers. This has been related to their sensitivity to hot temperatures, but where and in what state the flies spend the summer has remained unclear. Field enclosure experiments revealed no evidence for survival over summer in the pupal stage, as adults never emerged in early autumn from eggs laid in late spring. Laboratory and field evidence shows instead that adults acclimatize physiologically by suppressing reproduction in favour of accumulating lipid (but not glycogen) reserves. Apparently they spend the summer in cooler, forested areas close to the pastures. As reproduction is not entirely shut down, it is suggested that this represents quiescence rather than diapause. Presumably this increases the survival of the flies during the hottest time of the season, and appears to be a flexible life-history strategy, particularly for late-born spring generation individuals.     

Population persistence of the parasitoid fly Zaira cinerea (Fallén) (Diptera: Tachinidae) utilizing multiple host carabid beetles with different seasonality and quality

Zaira cinerea (Fallén) is a parasitoid fly (Diptera: Tachinidae) that attacks adult carabid beetles. To better understand mechanisms of population persistence in this species, we examined seasonality of host beetle abundance, the frequency of parasitism, and the timing of fly eclosion. In addition, we evaluated host quality using numbers of larvae or puparia per individual beetle as a measure of quality. The fly parasitized only large carabids (≥15 mm body length); the lengths of fly puparia reached 7.4–10.8 mm during development in beetle abdomens, and larger hosts are likely essential. Of the 18 large carabid species collected in this study, we chose two, Carabus maiyasanus Bates and Leptocarabus procerulus (Bates), because they were large and abundant (87% of total catch). The two carabids had different phonologies; C. maiyasanus was abundant from spring to summer, and its abundance dropped sharply in autumn, while L. procerulus was abundant in autumn and rare from spring to summer except July. Parasitism was observed in all the months from May to November except June, and adult flies eclosed more than once a year (in early summer, late summer, and mid‐autumn), indicating that the species is multivoltine. Host quality of L. procerulus was higher than that of C. maiyasanus. Carabus maiyasanus was mainly used as a host from spring to summer, and L. procerulus was used in autumn. Thus, adult beetles of one or both species are available over most of spring, summer, and autumn, allowing population persistence of this fly species over time.     

SEASONAL CHANGES IN FAVOURABILITY OF CATTLE DUNG IN CENTRAL QUEENSLAND FOR THREE SPECIES OF DUNG-BREEDING INSECTS

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The favourability of cattle dung from a native pasture near Rockhampton, Queensland, as a food source was tested monthly in the laboratory for 2 yr using 3 dung-breeding insects: the buffalo fly, Haematobia irritans exigua De Meijere; the bush fly, Musca vetustissima Walker; and a dung beetle, Euoniticellus intermedius (Reiche). Dung produced by cattle grazing on this pasture during the summer wet season yielded larger flies of both species and more broods from the dung beetle than dung from the same pasture in winter. When reared in summer dung, the buffalo fly almost attained its maximum recorded size but the bush fly and dung beetle reached ca two-thirds maximum recorded size and brood production respectively. Bush flies failed to breed in dung collected for 4 consecutive months in winter each year but survival of buffalo flies showed no seasonal trends.
The early response of the buffalo fly to improving dung quality in late winter/early spring gives it an advantage enabling its populations to increase earlier than those of its competitors, including the dung beetle, E. intermedius.     

Seasonal life cycle and autogeny in the mosquitoAedes togoi in northern Kyushu,Japan, with experimental analysis of the effects of temperature,photoperiod and food on life-history traits

We studied seasonal changes in the larval population structure, adult size, and autogeny (egg production without a bloodmeal) of the mosquitoAedes togoi on the seacoast of northern Kyushu, Japan. The effects of temperature, photoperiod and food conditions on larval development, adult size and autogeny were studied in the laboratory.Aedes togoi overwintered in both the egg and larval stages and was multivoltine. Adult size was greater in spring and autumn and smaller in summer. Autogeny occurred in spring and autumn but not in summer. Autogenous females were larger than anautogenous females, and larger autogenous females produced more eggs. Laboratory experiments showed that autogeny was promoted under low temperature and short-day conditions which corresponded with spring/autumn conditions in the field. Experimental food limitation in the larval stage greatly reduced adult size and autogenous egg production. In the field, large inter-pool variations in adult size and autogeny rate probably resulted from variations in nutrient and crowding conditions. Seasonal autogeny ofAedes togoi was discussed in terms of life-history strategy under fluctuating environmental conditions where relative advantages of autogenous and anautogenous reproduction alternate seasonally.     

Breeding of the bush fly,Musca vetustissima Walker,in an over-wintering area during winter and spring

Field experiments in an area of south-western Australia where bush fly (Musca vetustissima) adults occur permanently, showed that it overwintered by continuous breeding; but only two to three generations occurred between June and September. Low survival of eggs and larvae in the food (cattle dung) from May to August was associated with rainfall rather than low temperatures. High egg-adult survival occurred in late August; lower egg and larval survival in September and early October was attributed partly to dung fauna. Egg and larval survival was high in late October until December but predation or parasitization caused low survival of puparia outside the dung. Experimental and wild adult flies were largest and therefore most fecund in early spring; smaller wild flies in late spring appeared to result from larval competition for food. Simultaneous high egg-adult survival, high fecundity and rapidly decreasing generation times in late winter and early spring provide a basis for explaining the major increase in adult bush fly abundance observed in some areas in mid-spring.     

The bionomics of the free-living larvae and the transmission of Dictyocaulus filaria between lambs in North-East England.

The bionomics of the free-living larvae of Dictyocaulus filaria on pasture, and the transmission of infection between lambs, were studied during different seasons of the year in North-East England. The rate of development of first-stage larvae to the third stage took 4-9 days in late spring and summer, 1 1/2-4 weeks in autumn and 5 1/2-7 weeks in winter. The proportion of first-stage larvae developing to the third stage ranged from 10-28% in autumn and winter, and 2-25% in spring and summer. The rate of mortality of the third-stage larvae was approximately logarithmic in nature, although the survival time was shorter in spring and summer than in autumn and winter. Third stage larvae were able to survive from autumn until the spring of the following year in sufficient numbers to perpetuate transmission but not to cause clinical disease. In a transmission study, the survival of the infective larvae on the experimental plot was poor in summer, but the larval population increased in the autumn and then declined slowly throughout the winter. Infection in the susceptible lambs was related to the level of infection on the herbage increasing in severity from early summer to late autumn. However, those lambs infected in the summer were resistant to the heavy autumn challenge of larvae on pasture.     

Age structure of overwintered face fly populations estimated by pteridine concentrations and ovarian dynamics

Pteridines in the head capsules of face flies, Musca autumnalis DeGeer, were measured spectrofluorometrically to provide estimates of age. The flies also were dissected to determine ovarian development and fat body hypertrophy. Physiological ages in terms of degree-day accumulations were estimated among late autumn, winter, and early spring face flies. The reproductive history of eight overwintered face fly populations near Ames, Iowa, U.S.A., suggested that each had behaved as a single cohort, maturing their eggs and ovipositing according to a simple heat unit model. 83.8 +/- 16.4 degree-days above a 12 degrees threshold (DD > 12 degrees) were estimated to elapse between 1 January and the date at which 50% of overwintered cohorts had oviposited. Pteridine deposits indicated that diapausing females in late autumn had acquired a mean 96 +/- 36 DD > 9.8 degrees and the males 135 +/- 39 DD > 9.8 degrees. Soon after emergence from hibernaculae, females were average physiological ages of 135 +/- 25 DD > 9.8 degrees and the males were 152 +/- 28 DD > 9.8 degrees. Mean physiological age of overwintered females was 155 +/- 37 DD > 9.8 degrees compared with 110 +/- 38 DD > 9.8 degrees among parous flies in summer. Overwintered males in spring were an average 175 +/- 41 DD > 9.8 degrees compared with 144 +/- 65 DD > 9.8 degrees among summer flies.     

The phenology of Onitis alexis (Coleoptera: Scarabaeidae) in the Araluen Valley: Survival in a marginal environment

The introduced African dung beetle, Onitis alexis Klug, has become established in the warmer regions of Australia. The south-eastern limit of its current distribution is Moruya, NSW, and the Araluen Valley 50 km inland. At Araluen newly emerged beetles are present in dung in late spring, summer and autumn. Egg-laying starts 1-2 weeks after emergence and continues throughout the summer and autumn, as indicated by the presence of parous females in the population and of broods under experimental pads. Eggs laid in December/January produce adults in late summer and autumn, those laid from February to April produce adults in the following spring and summer. In the laboratory, mortality of larvae is high in cold (0–16°C), wet conditions and their development is delayed in warm (25°C and 27°C), dry conditions. This delay was confirmed in the field during the summer drought of 1982-83 when predicted times of emergence (based on day-degree summation in the soil) always preceded the observed emergence time of the local population, as well as preceding the emergence of beetles developing from eggs laid at known times. Follicle resorption in adult females was related directly to increasing age and to rainfall. Dung collected from hayed-off pasture did not affect fecundity, but caused larval mortality. Adults survived the winters at Araluen in some years, and immatures survived best during dry winters, being facilitated in this by a cold-induced larval diapause. Onitis alexis larvae can survive wet or dry summers, and cold dry winters (down to about 0°C) but not wet winters. This seems to be the major factor limiting the southern distribution of the species.     

RELATION BETWEEN OVARIAN MATURATION AND ACTIVITY OF THE CORPORA ALLATA IN SEASONAL FORMS OF THE BUTTERFLY, POLYGONIA C-AUREUM L.

In summer form adults of Polygonia c-aureum, the ovary develops soon after emergence and eggs mature a few days later. However, in autumn form adults, having been kept in laboratory conditions, only several mature eggs are found about four weeks after emergence. The allatectomy during the larval period prevents egg maturation in adults of both forms. When the corpora allata from the summer form of both sexes are transplanted into allatectomized adults of the autumn or summer form, the ovary develops as in the case of summer form adults. But the corpora allata of both sexes of the autumn form are not effective in inducing the ovarian maturation. Environmental factors, especially day-length and temperature during the larval period, may act through the neuroendocrine system to induce the activity of the corpora allata in the adult life.     

Olfactory responses of the omnivorous generalist predator Dicyphus hesperus to plant and prey odours

This paper describes a method for studying the neighbourhood (dispersal) movement of pest insects that overcomes the major problems associated with release/recapture experiments. The method has been developed using the carrot fly, Psila rosae (Fab.) (Diptera: Psilidae), as the experimental insect. It involves building up a large population of insects in an area free of other host plants, and then, as the insects disperse in the spring, monitoring the fall‐off in numbers of insects with increasing distance. Estimates of the fall‐off in numbers of the carrot fly were obtained by using sticky traps to monitor changes in fly numbers in 11 small plots of carrots drilled 130–1300 m away from the site at which the flies emerged (emergence site) in the spring. A strong linear relationship (r² = 0.96) was obtained between the log₁₀ numbers of flies caught in each plot and the log₁₀ distance the plot was from the emergence site. Few flies were caught more than 1 km from the emergence site. A linear relationship (r² = 0.86) was also obtained between the date when 50% of the flies were caught in each plot and the distance the plot was from the emergence site. The date of 50% capture was delayed by 1 day for each 100 m the given plot was away from the emergence site. This suggests that when carrot flies move to find new crops, the population moves about 100 m day^?1. About one million flies would have to be released in conventional release/recapture experiments to obtain data as robust as those collected using the current method. The major breakthrough of this method is that dispersal can be estimated for an insect species that, although a major pest of field crops of carrots and parsnips, is exceptionally difficult to rear, even in relatively small numbers, under controlled‐environment conditions.     

Materials for a study in animal competition

The incidence of the sewage fly, Psychoda alternata Say, breeding almost free from other insect competitors in a bacteria bed at Huddersfield is examined. Its general seasonal trend is marked by periods of peak output explained on the theory that there are two successions of generations running persistently and alternating with one another. Such behaviour has previously been demonstrated for another sewage fly, Spaniotoma minima , and has been shown to be instituted by irregular temperatures in autumn and spring. In Psychoda alternata a special type of intraspecific competition is set-up in the warmer months when the cycles are rapid, for the larvae of one succession must start life in a bed just depleted of food by the other. Therefore large and small outbursts of the fly tend to alternate. The discharges of solids from the bed have a detailed periodicity corresponding to the alternations in the successions of the fly.     

Seasonal succession of ciliates in lake constance

We found a recurrent seasonal pattern in abundance and composition of planktonic ciliates in Lake Constance, FRG, over a three-year period. Abundance peaks occurred in early spring and summer/autumn, while ciliate numbers were low in late spring (clear-water phase) and winter. Prostomatida and Oligotrichida dominated in early spring. They responded immediately to the phytoplankton spring bloom, while Haptorida, Peritrichida, and large Scuticociliatida (Histiobalantium) were delayed by 1 to 2 weeks. The spring community broke down at the onset of the clear-water phase.Pelagohalteria viridis containing symbiontic algae appeared shortly after this event. A highly diverse community was recorded in summer/autumn. Peritrichida, small Oligotrichida, and large Scuticociliatida reached their maxima during this season. Small Scuticociliatida were rare throughout the year and contributed moderately to total ciliate numbers only during the cold season. The observed seasonal sequence of pelagic ciliates in Lake Constance is discussed in relation to simultaneously collected data on potential food organisms and grazers.     

SEASONAL ABUNDANCE OF MUSCA VETUSTISSIMA WALKER AND OTHER CATTLE DUNG FAUNA IN CENTRAL AUSTRALIA

Abstract
Bush flies, Musca vetustissima attracted to a human, and arthropod fauna attracted to fresh cattle dung in 24 hours, were sampled every 2 weeks for 2 years (1980–1982) near Alice Springs in central Australia. Substantial rain fell in both summers, but it was more prolonged in the second. The bush fly occurred and bred throughout the year, although its abundance was usually low. The only major increase in bush fly abundance occurred after the first summer's rainfall caused the growth of new herbage. This was followed by increased feeding on dung by adult flies and intensified breeding. Bush fly abundance was low in the second summer, despite evidence of a long period of continuous breeding. A variety of dung-feeding and predatory beetles and also mites was almost always present, although numbers were usually low. The introduced dung beetles Euoniticellus intermedius and Onthophagus gazella numerically dominated samples. Dung fauna abundance also increased after significant rainfall, particularly in the second summer. Dissections of the dung beetles showed that they bred at these times.     

Bovine thelaziasis in Iowa

The prevalence of developing Thelazia nematodes in face flies (Musca autumnalis) was studied for 7 yr at a beef farm in central Iowa. Juvenile nematodes were not found among flies in reproductive diapause in autumn, nor among nulliparous, overwintered flies in spring, but only among actively reproducing insects. Thus Thelazia probably do not overwinter in face flies. A mean prevalence of 2.0% infected was recorded among flies in 7 fly breeding seasons. No heterogeneity in Thelazia prevalence was detected within fly breeding seasons. The frequency distribution of Thelazia among face flies by year of occurrence was homogeneous, with a mean of 2.75 larval nematodes per infected fly. Thelazia gulosa and T. skrjabini were recovered in necropsy from the eyes of bovines from central Iowa. Prevalence among fat cattle 18-27 mo old was 15%; among cows 3-15 yr old, prevalence was only 3%. Thelazia skrjabini was found in 29 eyes and T. gulosa in 4 eyes. Infections were randomly distributed among the eyes of subject cattle. The mean worm burden was 2.3 T. skrjabini and 12 T. gulosa per infected eye. Thelaziasis is clearly enzootic in Iowa.     

洞庭湖区东方田鼠的食物组成调查

采用胃内容物显微组织学鉴定法,定量调查了洞庭湖区东方田鼠（Ｍｉｃｒｏｔｕｓｆｏｒｔｉｓｃａｌａｍｏ－ｒｕｍ）的食物组成。该鼠的主要食物,在苔草地是苔草和水田碎米荠,在芦荻场是碎米荠、苦草、荻和镜子苔,在稻田区是水稻和双穗雀稗,在岗地是三毛草、一年蓬、千金子和水稻。植物叶片是其主要利用对象,在绿色食物资源不足的情况下,也取食植物种子。其食物组成的变化表明,该鼠能依不同栖息地的植被结构调整摄食对象,因而能适应湖区生活环境的灾变性变化。     

Growth and development of Australian soldier fly,Inopus rubriceps (Diptera: Stratiomyidae), in New Zealand

Abstract

Larvae of Inopus rubriceps (Macquart) were reared from eggs originating from spring and autumn adult emergence periods (1975–78), under both insectary and field conditions. Rate of development appeared to depend largely on temperature. Autumn-hatched larvae showed little growth for the initial 6 months, but then grew rapidly until the end of summer. Spring-hatched larvae also grew rapidly over summer, but their development slowed over winter. Year-to-year differences were found in larval survival, weight gain, and rate of development, and in subsequent adult emergence. Pest status appeared to be related to the cumulative yearly heat budget. Overall, larval survival was higher and growth and development were more rapid in the insectary than under field conditions. A male-dominant sex ratio was demonstrated.