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.     

The seasonal distribution and characteristics of bush fly Musca vetustissima Walker populations in south-western Australia

In the agricultural region of south-western Australia the bush fly Musca ventustissima Walker was found to occur permanently in the north-eastern half but it died out during winter in the south-west. The abundance of bush flies increased rapidly throughout the overwintering zone in early spring as a result of local breeding. Flies then dispersed south-westwards, completely repopulating the region during October. Immigrant flies were large and therefore highly fecund, and of advanced reproductive maturity. Local breeding then rapidly increased the population. Maximum abundance occurred in mid-spring in the north and east and in early summer in the south and west. Abundance was greatest in the north where large overwintering populations occurred, and in the far south where repopulation occurred early in the seasonal cycle of pasture growth so that the more favourable cattle dung produced flies that were more fecund than their immigrant parents. The abundance of bush flies declined throughout the region in summer, to negligible levels near the south-west coast but, paradoxically, higher levels occurred inland where there were fewer cattle. On average, flies were smaller and reproductively younger in summer. In areas where irrigated pastures produced more favourable dung in summer, the patterns of abundance and other characteristics of flies did not differ substantially from those in comparable non-irrigated areas. The abundance and other characteristics of a bush fly population 10 km from a cattle-grazing breeding site were similar to those at the site, indicating that constant dispersal is the basis of the bush fly's ubiquity.     

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.     

Influence ofOnthophagus gazella on hornfly,Haematobia irritans density in irrigated pastures

Haematobia irritans (L.) breeding in flood irrigated pastures of the lower Colorado Desert of southeastern California continues to remain unacceptably high during warm seasons (>1,000 adult flies per bovine head) despite the presence of moderately abundant populations ofOnthophagus gazella F. This study suggests that densities of > 40–70 adult beetles per dung pad and giving pronounced dung shredding activity, caused fly mortality of 38–56 %. The continued high abundance of adult horn flies on cattle suggests that at > 50% mortality, the pasture environment still produces sufficient flies to saturate cattle, although emigration might be reduced. Additional species of scarabs may be necessary to increase fly mortality. However, the dung drying activity of existingO. gazella significantly could interfere with resident staphylinid beetle breeding, which was significantly lower in pastures whereO. gazella reached densities of 40 per dung pad. Scarab beetle activity might also impede the introduction of superior predatory species for biological control.      

Populations of the bush fly (Musca vetustissima Walker) in arid Australia

Populations of the bush fly Musca vetustissima were usually low in arid south-western Australia. Herbaceous plants that grew only after rain resulted in changes to cattle dung that increased its attractiveness to bush flies for oviposition in laboratory tests. Larvae reared in such dung consistently produced large flies of high fecundity, and larval survival was usually high. Similar responses to the dung were evident from examination of flies sampled in the field. Although greatly increased bush fly abundance was possible only after major improvement in cattle dung, it was not a general phenomenon as immature survival did not always increase. Even major population increases resulted from periods of high immature survival that were brief relative to the duration of favourable dung. Nematodes Heterotylenchus sp. appeared to be an important mortality factor of the immature stages at such times. Build-up of high bush fly populations occurred only in cattle-grazing areas, but base-level abundance was similar regardless of the presence of cattle. Almost all female flies were gravid when cattle dung was unfavourable for breeding, and in areas without cattle. In arid areas, acceptable oviposition sites probably are more limiting than are sources of protein for oögensis.     

Dividing the pie: differential dung pat size utilization by sympatric Haematobia irritans and Musca autumnalis

Horn flies [Haematobia irritans (Diptera: Muscidae) (L.)] and face flies [Musca autumnalis (Diptera: Muscidae) De Geer] use the same larval resource, but their interactions are poorly studied. Dung pats (n = 350) were core sampled in the summers of 2012 and 2013 from irrigated pastures in Pomona, California, U.S.A. (34°03′N, 117°48′W) and held for face fly and horn fly emergence. Surface areas and estimated weights were recorded for each whole pat. Almost half (42.0%) of the pat cores yielded neither fly, 29.7% yielded horn flies only, 12.9% yielded face flies only and 15.4% yielded both flies. Of the fly‐positive pats, surface area and mass were larger for face fly‐occupied pats, whereas horn fly‐occupied pats were smaller. Pats shared by the two species were intermediate. Horn flies per positive core were unaffected by the absence/presence of face flies, but half as many face flies emerged when pats were co‐inhabited by horn flies. Face flies inhabited larger pats, which might better resist heating and drying, to which they are susceptible; horn flies inhabited a broad pat size range. Horn fly tolerance of lower dung moisture probably allows horn flies to colonize and survive in a wide range of pats in dry areas like southern California.     

Succession and fluctuation in Artemisia dominated grassland

Vegetation dynamics were studied from 1940 to 1978 in two grazed pastures and associated exclosures in sand sagebrush (Artemisia filifolia) dominated grassland, western Oklahoma, USA. In both pastures and one exclosure, pattern of vegetation change reflected fluctuation rather than succession. In the other exclosure, the grassland exhibited a directional change from annual grasses and forbs to dominance by perennial grasses. Rate of change was consistent during the 39 year period. Cover of grasses increased more in grazed than ungrazed areas. Grass cover was negatively correlated with high air temperatures early in the growing season. Forb cover remained relatively constant over time and shrub cover peaked during the 1960s. Abundance of annuals and cool season species was positively correlated with rainfall early in the growing season.Species diversity and richness were lowest in the ungrazed areas, as a result of increased dominance by perennial grasses such as Schizachyrium scoparium. In pastures and exclosures, richness was positively correlated with growing season precipitation. Cover of the common species differed among sample areas within years and fluctuated between years. Few general patterns emerged from correlations of environmental variables with cover of individual species. In general, vegetation dynamics in these sand sagebrush grasslands reflect a tradeoff in that total cover changes little over time because the loss of some species is compensated for by increased growth of others. Such trade-offs reflect the individualistic response of the component species within each pasture or exclosure. Although changes in growth form composition were related to climatic fluctuation, broad-scale climatic variables could not successfully predict small-scale patterns of change by individual species over time.     

Winter feeding sites of hay in round bales as major developmental sites of Stomoxys calcitrans (Diptera: Muscidae) in pastures in spring and summer

The stable fly, Stomoxys calcitrans (L.), historically has been a pest of livestock in confined operations but seldom of animals on pastures or rangelands. In the past two decades, however, S. calcitrans has become a major pest of cattle and horses on pastures in the midwestern United States. Although there usually is an overabundance of diverse stable fly and house fly, Musca domestica L., larval habitats in confined livestock operations, no larval habitat for stable flies has been clearly identified in the pasture-range environment. Because the winter feeding of hay in round bales results in significant amounts of hay wastage that when mixed with manure, might develop into suitable larval habitats, this study evaluated these areas as developmental sites for the abundant stable flies in pastures. There was a trend for fly traps placed in the vicinity of hay feeding sites to catch more stable flies than those placed distant from these sites. Estimates of stable flies emerging from these sites ranged from 102 to 1225 flies per core sample (25 by 25 cm). The mean number of adult stable flies during May and June 2001 through 2004 correlated negatively with the average minimum temperatures during the preceding winter (November-February) but not with rainfall or temperatures during the spring. These results support the hypothesis that winter feeding sites of hay in round bales are the main source of stable flies in pastures.     

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 relationship between dung quality and oocyte resorption in laboratory and field populations of Lucilia cuprina

Oocyte resorption in Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae) is indicative of protein shortages during ovarian development. It is commonplace in field populations and is thought to reflect the species’ dependence on sheep dung as its primary source of protein. To test this proposition, resorption was monitored in flies fed with sheep dung collected when pastures varied from lush to drought affected. Laboratory assays showed that the proportion of females that became gravid, their rate of ovarian development, and the size and number of oocytes matured all decreased significantly as the protein content of the food source decreased. Conversely, the number of oocytes resorbed increased as dung protein decreased. However, estimates of dung quality (DQ), as derived from a pasture growth–DQ model, were not informative in explaining the seasonal or regional prevalence of resorption in flies collected over several years in three widely disparate sheep‐grazing areas. Recalibration of the DQ model to provide daily estimates of dung protein, which were then used to predict the incidence of oocyte resorption at different times of the year, also failed to show any systematic effects. There was, however, a clear tendency for this model to underestimate the extent of resorption in field populations. Because wild flies would have ready access to a wide variety of food sources, many of which would have been more nutritious than sheep dung, this finding is contrary to expectation and hence the nutritional role of sheep dung merits further study.     

Moose–vehicle collisions occur earlier in warm springs

After autumn, early summer is the most important moose–vehicle collision (MVC) season in Finland. We surveyed temporal distributions and long-term changes in the timing of MVCs using data of daily collisions that occurred throughout a 4-month season (April–July) for the period 1989–2011. By uniting the road districts, we first divided Finland into five study regions and calculated the annual dates by which 50 % of all the MVCs of the study season had taken place (median dates). Then, using all of the present nine road districts as areal units, we determined if the beginning of the growing season and the median dates of MVCs were correlated. A total of 13,233 MVCs occurred during the study period. In every region, considering the selected 4-month annual period, the number of MVCs was the lowest in April but started to increase in May and was highest in June or July. The timing of the median dates for MVCs in all regions shifted to an earlier date and was positively correlated with the beginning of the growing season in every road district. We believe that the beginning of the growing season correlates with the timing of moose spring migration from wintering areas to summer pastures and further, with the timing of MVCs. Regardless of the ultimate reason behind our findings, we emphasize the practical importance of our results, namely how the onset of spring can help predict timing of spring MVCs. We recommend that warning campaigns informing road users coincide with the annually changing MVC season.     

Spatiotemporal patterns of taxonomic and functional β-diversity of dung beetles in native and introduced pastures in the Brazilian Pantanal

Anthropogenic activity, such as conversion and degradation of habitats, is causing global biodiversity declines. However, our understanding of how local ecological communities are responding to these changes taxonomically and functionally is still limited. The effects of the replacement of native by introduced pastures on biodiversity are some of those examples with limited understanding. Here, we sampled dung beetles in native and introduced pastures using standardised sampling protocols during the dry and rainy seasons in the Brazilian Pantanal. We used multifaceted β-diversity partitioning of taxonomy-, abundance- and trait-based approaches to evaluate spatial (i.e. between pasture types) and temporal (i.e. between seasons) patterns of dung beetle changes in composition, abundance and species traits. Spatially, we found no effects of pasture type, season and their interaction on taxonomy-based β-diversity and its components. For abundance-based β-diversity and its components, pasture type had effects on both Bray-Curtis dissimilarity and balanced variation in abundance. Higher values of both metrics were found in native pastures. For functional-based β-diversity, Sorensen dissimilarity with higher values in the dry season, while pasture type also had an effect on functional nestedness, where higher values of functional nestedness were found in introduced pastures. Seasonally, we also found no effects of pasture type, season and their interaction on taxonomy-based β-diversity and its components. However, pasture type had effects on Bray-Curtis dissimilarity, with higher values found in introduced pastures. No effects on balanced variation in abundance and abundance gradients were found. Pasture type influenced the functional turnover, but not functional dissimilarity or nestedness. Higher values of functional turnover were found in native pastures. In summary, we demonstrate that the type of pastures and climatic seasonality have effects on abundance- and functional- but not on taxonomy-based β-diversity patterns of dung beetles in the Brazilian Pantanal.     

Response of the dung beetle community to different climatic zones: Does the land use system matter?

The conversion of Brazilian savanna into exotic pastures leads to the loss of dung beetles and a decrease in their contribution to ecological functions. We hypothesized that the dung beetle communities from exotic pastures would show greater significant differences between climatic zones, when contrasted to communities from Brazilian savanna in the same region, since dung beetle assemblages in pastures are more simplified. We assessed which variables (purpose of production, type of management, percentage the habitat per buffer, soil penetration resistance, pasture area and herd size) affect more the dung beetle community in exotic pastures. We carried out this study in 48 areas of native Brazilian savannas and exotic pastures distributed across four bioclimatic zones: BZ1, hot with three dry months; BZ2, hot with 4–5 dry months; BZ3, sub-hot with 4–5 dry months and BZ4, meso-thermal with 4–5 dry months of Minas Gerais State, Brazil. In each BZ, six areas of Brazilian savannas and six areas of exotic pasture were selected. In the Brazilian savanna areas, the species richness, abundance and biomass of dung beetles did not differ between the bioclimatic zones, unlike the exotic pastures. The composition of the dung beetle community was different between land use systems and between bioclimatic zones; the interaction between the two factors was also significant. Our results provide evidence that dung beetle communities active in exotic pastures are more susceptible to climatic environmental variations than communities from more complex and stable habitats, such as savannas. Finally, the best model suggested that all the six variables combined explained about 91% of the total variability in species composition observed between sampling sites.     

Mating Status and Choice of Group Size in the Phoretic Fly Norrbomia frigipennis (Spuler) (Diptera: Sphaeroceridae)

The phoretic sphaerocerid fly Norrbomia frigipennis mates on scarabid dung beetles, follows them underground, and lays eggs in the collected dung. We found that male and female flies distribute themselves nonrandomly on beetles with respect to fly group size. The proportion of virgin females increased with group size, and females with mature eggs were most frequently found on beetles carrying fewer flies. Laboratory experiments revealed that mated females avoided larger groups, virgin females seemed to prefer large groups and mated females, small groups. Males showed no such pattern. These results suggest that N. frigipennis can estimate group size, presumably an adaptation with a reproductive function. However, flies did not join hosts on the basis of the sex of already mounted flies.     

Seasonal variation of the capture and field distribution of sterile Anastrepha ludens in Tamaulipas,Mexico

Anastrepha ludens (Loew) (Diptera: Tephritidae) is one of the most important citrus pest in Mexico. The sterile insect technique (SIT) is used against pest populations of fruit flies for suppression, eradication, containment and prevention to reduce damages in fruit‐growing areas. In this study, we analyzed the seasonal variation of captures and field distribution of sterile A. ludens released in different seasons of the year in north‐eastern Mexico. Chilled releases were conducted by air at constant densities per ha on a citrus area for a period of 32 weeks that included the coldest and warmest seasons that is winter, spring and summer. Multilure traps baited with torula yeast pellets were used to capture sterile flies. Fly capture data were compared over the three seasons and correlated with climate. The lowest number of captures of the sterile insect occurred in the summer and the highest in winter and spring. High and low temperatures were negatively correlated with fly captures. Field distribution was also negatively correlated with high temperatures in summer, but no relationships were observed in winter and spring. No relationships were observed between rainfall with capture and field distribution of sterile flies. These results indicate that summer is a season involving agro‐ecological and environmental constraints for the capture and field distribution of sterile flies. This study may be useful for enhancing release strategies and optimizing economic resources in north‐eastern Mexico. Further research on the behaviour of sterile flies under stressful environments is suggested.     

Effects of avermectin residues in cattle dung on yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae) populations in grazed pastures

The effects of avermectin exposure on natural populations of the yellow dung fly, Scathophaga stercoraria Linnaeus, were investigated at the field scale on farms in south-west Scotland. Pastures forming the focus of the study were grazed with either untreated cattle or cattle receiving standard, manufacturer-recommended treatment regimes of an avermectin product. Flies were sampled between April and July in 2002 and 2003 using dung-baited pitfall traps. Abundance and wing asymmetry in S. stercoraria populations were examined in relation to a range of environmental and management variables (including avermectin exposure, pasture management intensity, weather and season). Data used for abundance analyses were collected in fields where treated cattle had been dosed with either doramectin or ivermectin, while the data for the asymmetry analyses were from a subset of fields where treated cattle had been dosed with doramectin only. While abundance of S. stercoraria varied significantly between years and with season, there was no difference in their abundance between fields grazed by avermectin-treated or untreated cattle. Asymmetry was significantly higher in fly populations in fields grazed by doramectin-treated cattle, suggesting that exposure to doramectin during development could have imposed some degree of environmental stress. While these results suggest that exposure to doramectin residues in dung on grazed pastures may have sublethal effects on the insects developing in that dung, there was no evident avermectin effect on the abundance of adult S. stercoraria occurring in the pastures.     

Are Dung Beetles Driving Dung-Fly Abundance in Traditional Agricultural Areas in the Amazon?

We evaluated the effects of different land-use systems on the ability of dung beetles to control the population of detritus-feeding flies. We tested the hypotheses that intensification of land use will reduce dung beetles richness, abundance and biomass and, consequently, their dung burial ability, affecting the interaction between dung beetles and flies and reducing its effectiveness as a natural biological control. In the Brazilian Amazon we sampled dung beetles, fly larvae and adults; and recorded the rate of dung removal by dung beetles across a gradient of land-use intensity from primary forest, secondary forest, agroforestry, agriculture to pasture. Our results provide evidence that land-use intensification results in a reduction of the richness, abundance and biomass of dung beetles, and this in turn results in lower rates of dung removal in the most simplified systems. We found no significant differences in the abundance of fly larvae between the different systems of land use. However, the number of adult flies differed significantly between land-use systems, presenting higher abundance in those sites with greater intensity of use (pasture and agriculture) and a lower abundance of adult flies in forested systems (primary and secondary forests, and agroforestry). Information-theoretic model selection based on AICc revealed strong support for the influence of land-use systems, dung removal rates and dung beetle abundance, biomass and richness on adult dung-fly abundance. Our results also reveal that dung beetles are not solely responsible for fly control and that other factors linked to land use are influencing the populations of these detritus-feeding insects.     

River confluences enhance riparian plant species diversity

In riparian zones along the banks of streams and rivers, flooding often causes large changes in environmental conditions immediately downstream of confluences. In turn, spatial heterogeneity in flooding along rivers and streams likely affects local species diversity. Furthermore, flooding during the plant growing season can strongly affect plant survival. In this study, we hypothesized that confluences have impacts on plant species diversity, and that these impacts are larger during the plant growing season. To test this hypothesis, we measured plant species diversity and the extent of natural bare ground at 11 river confluences during two different seasons (summer and spring) within the Mukogawa River basin system, Japan. Species diversity was highest at down-confluence areas in the summer. We linked the pattern of species diversity to that of bare ground creation by floods around the confluences and to the seasonality of annual plant recruitment. The extent of bare ground was significantly greater at down-confluence areas than at up-confluence areas. The recruitment of annual species was higher in the summer than in the spring and included rapid occupancy of bare ground in the summer. We suggest that within river systems, spatial and seasonal differences in patterns of flooding function together to regulate plant species diversity.     

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.     

Reproductive ecology of the jacky dragon (Amphibolurus muricatus): an agamid lizard with temperature‐dependent sex determination

Abstract The jacky dragon, Amphibolurus muricatus (White, ex Shaw 1790) is a medium sized agamid lizard from the southeast of Australia. Laboratory incubation trials show that this species possesses temperature‐dependent sex determination. Both high and low incubation temperatures produced all female offspring, while varying proportions of males hatched at intermediate temperatures. Females may lay several clutches containing from three to nine eggs during the spring and summer. We report the first field nest temperature recordings for a squamate reptile with temperature‐dependent sex determination. Hatchling sex is determined by nest temperatures that are due to the combination of daily and seasonal weather conditions, together with maternal nest site selection. Over the prolonged egg‐laying season, mean nest temperatures steadily increase. This suggests that hatchling sex is best predicted by the date of egg laying, and that sex ratios from field nests will vary over the course of the breeding season. Lizards hatching from eggs laid in the spring (October) experience a longer growing season and should reach a larger body size by the beginning of their first reproductive season, compared to lizards from eggs laid in late summer (February). Adult male A. muricatus attain a greater maximum body size and have relatively larger heads than females, possibly as a consequence of sexual selection due to male‐male competition for territories and mates. If reproductive success in males increases with larger body size, then early hatching males may obtain a greater fitness benefit as adults, compared to males that hatch in late summer. We hypothesize that early season nests should produce male‐biased sex ratios, and that this provides an adaptive explanation for temperature‐dependent sex determination in A. muricatus.