Temperature effects on development and survival of two stable flies, Stomoxys calcitrans and Stomoxys niger niger (Diptera: muscidae), in La Réunion Island

Stable fly activity is associated with dairy management practices and seasonal weather conditions

Stable flies (Stomoxys calcitrans) are blood-sucking insects commonly associated with cattle production systems worldwide and are known to cause severe irritation to cattle due to painful bites. Cattle react to biting stable flies with an aggregating behavior known as bunching. Bunching behavior reduces grazing or feed consumption and thus reduces cattle productivity and welfare. Cattle’s fly-repelling behaviors include foot stomping, head tossing, tail switching and skin twitching. A longitudinal study was conducted in 2017 on 20 California dairies (average lactating herd size = 2,466 (SE±28.392)) during the stable fly season from April to July. The study objectives were to estimate the association between environmental factors and dairy characteristics including facility design, feed and manure management, total mixed ration (TMR) components fed to cattle, and operational pest management procedures and the outcome stable fly activity on California dairies. Stable fly activity was measured by counting stable flies on cow forelimbs (leg count) and on Alsynite traps (trap count) over the 13-week study period. Weekly leg counts were performed for cattle in lactating cow pens (31 pens from 10 study dairies) with counts made during the morning (AM) and again during the afternoon (PM). Trap counts were performed on all 20 study dairies. Data were analyzed using linear mixed models which revealed temporal variation in the average leg and trap counts with stable fly activity increasing from May to June and then decreasing to the lowest activity in July. Leg counts were higher during the afternoon compared to morning. Ambient temperatures ≤30⁰C and relative humidity (RH) measurements <50% were associated with higher leg and trap counts. Traps located at the periphery of study dairies had higher stable fly counts compared to traps located in the interior of the dairy. Cow pens with trees on the periphery had higher leg counts in comparison to pens away from trees. Specific TMR components were associated with both leg and trap counts. Dairies feeding by-products including almond hulls, wet distillers’ grain, fruits, and vegetables had higher trap counts compared to dairies that did not feed these ingredients. At the pen level, pens with rations that contained straw had lower average leg counts compared to pens fed with rations that did not contain straw. A similar association was observed for pens with rations that contained wheat silage when ambient temperatures were ≤30⁰C. In contrast, pens with water added to the TMR while the RH was ≥50% had higher average leg counts compared to pens without water added to the TMR. Dairies that applied insecticides for fly control to their entire facility had lower trap counts compared to dairies that did not apply insecticides. Stable fly activity measured on California dairies using leg and trap counts varied according to the month, environmental factors, pen surroundings, trap location, TMR components, and insecticide use.

The combined effects of temperature and relative humidity parameters on the reproduction of Stomoxys species in a laboratory setting

In this study, Stomoxys species (S. calcitrans, S. sitiens and S. indica) were examined to improve on the current technique for mass rearing using a method of combined incubation parameters. Moreover, the reproductive potential of immature forms at various stages of development was defined. Immature forms of stable flies were incubated according to species. There was no significant difference in the number of immature forms obtained among species incubated under the same conditions. Six incubation parameters were used in combination, at temperatures (T) of 32°C, 27°C and 22°C and relative humidity (RH) of 90% and 70% RH. The combined method resulted in a higher number of eggs hatching at 32°C and 90% humidity as well as an increase in the number of larva pupated and emergence of imago at 27°C and 70% humidity.

Effects of Diet Quality and Temperature on Stable Fly (Diptera: Muscidae) Development

The effects of diet quality and temperature on the development time and size of stable flies, Stomoxys calcitrans (L.), was evaluated. Both development time and size varied relative to diet quality and temperature, and their effects were additive. Diet quality and temperature made similar contributions to the variance in size whereas temperature was responsible for >97% of the variance in development time. Regression analysis predicted the shortest development time, egg to adult, to be 12.7 days at 32 °C and 70% nutrients. Egg to adult development varied curvilinearly relative to diet quality and temperature on the degree day 10 (DD10) scale taking 261 DD10 at 30 °C and 50% nutrients. The thermal threshold was 11.5 °C with a thermal constant of 248. Very few stable flies developed to adult on the poorest diet (12.5% nutrients) and adults emerged from fewer than 1% of the puparia at 35 °C. The heaviest pupae (15.4 mg) were produced with the 100% diet at 15 °C and adults had a higher probability of emerging successfully from heavier puparia. The length of the discal-medial cell of adult wings had a cubic relationship with puparia weight and peaked at 21 °C. Egg to pupariation survival was predicted to peak at 27 °C and 71% diet whereas puparia to adult survival peaked at 24 °C and 100% diet. Diet quality and temperature had no effect on sex ratio and the rate of development did not differ between the sexes. Female stable flies were ≈5% larger than males. Composite metrics for egg to pupariation and egg to adult fitness were developed. The optimum for puparia fitness was 29 °C and 78% diet quality and for adult fitness 25 °C and 83% diet quality. Diet accounted for 31% of the variance in pupal fitness and 24% of the variance in adult fitness whereas temperature accounted for 17% and 20%, respectively.

The Factors Influencing Seasonal Dynamics and Spatial Distribution of Stable Fly Stomoxys calcitrans (Diptera, Muscidae) within Stables

The biology of the stable fly is fairly well known, but factors influencing the distribution of adult stable flies within stables are still inadequately investigated. The four experimental stables were located in south western Slovakia. Within each stable, five sticky traps were localized along the stable, and the flies were weekly counted during the flight season of years 2015–2017. Seasonal activity and stable fly abundance in relation to temperature, rainfall, light conditions, relative air humidity, and cows per stable were evaluated. The seasonal activity of the stable fly shows one large peak at the end of summer and a second smaller peak just before the end of the flight season. The spatial distribution of stable flies was unique for each stable. All of the environmental variables had significant and mostly positive effect on stable fly abundance. The strongest and most positive effect on stable fly counts was temperature and rainfall five weeks prior to collecting session. Within the stable, cow number, air humidity, and light conditions are the strongest candidates to influence their distribution.

Predicting nuisance fly outbreaks on cattle feedlots in subtropical Australia

Flies are important arthropod pests in intensive animal facilities such as cattle feedlots, with the potential to cause production loss, transmit disease and cause nuisance to surrounding communities. In the present study, seasonal population dynamics of three important nuisance flies, namely house flies (Musca domestica L.), bush flies (M. vetustissima Walker) and stable flies (Stomoxys calcitrans L.) (Diptera: Muscidae), were monitored on cattle feedlots in south-eastern Queensland, Australia, over 7 years. Musca domestica was by far the dominant species, comprising 67% of the total flies trapped. Models were developed to assess the relationship between weather parameters and fly abundance and to determine whether population trends could be predicted to improve the timing of control measures. For all three species, there were two main effects, namely time-of-year (mainly reflected by minimum temperatures and solar radiation) and rainfall. The abundance of all three species increased with increasing temperature and rainfall, reaching a peak in summer, before decreasing again. Rainfall events resulted in significantly elevated numbers of M. domestica for up to 5 weeks, and for 1 week for M. vetustissima. Peak fly numbers were predicted by the model to occur in spring and summer, following 85–90-mm weekly rainfall. The population dynamics of S. calcitrans were least influenced by rainfall and it was concluded that weather variables were of limited use for forecasting stable fly numbers in this environment and production system. The models provide a useful tool for optimising the timing of fly-control measures, such as insecticide or biopesticide applications, adding to the efficiency of integrated control programs.

Modeling the Temperature- and Age-Dependent Survival, Development, and Oviposition Rates of Stable Flies (Stomoxys calcitrans) (Diptera: Muscidae)

Stable flies (Stomoxys calcitrans (L.)) can be a serious pest associated with cattle facilities. In Denmark, they occur most abundantly at organic farms, where they cannot be controlled by means of insecticides. On traditional farms, where chemical control is widely used, development of resistance is of increasing concern. Therefore, interest in biological control or other alternative methods has been growing during the recent years. In order to understand the complex relationships between a pest and its natural enemies in a variable environment, it is necessary to know how temperature affects the dynamics of the involved species. In this paper, we apply data derived from several existing sources to investigate the influence of temperature on development and survival of eggs, larvae, pupae, and adult stable flies, as well as on the fecundity of adult females. We demonstrate that the same modeling framework (called SANDY), previously applied to lifetable data of the pteromalid pupal parasitoid (Spalangia cameroni Perkins), a biological control agent used against stable flies, can also be used to model S. calcitrans. However, the predicted temperature responses depend on the data sources used to parameterize the model, which is reflected by differences in estimated population growth rates obtained from American and non-American studies. Elasticity analysis shows that growth rates are more sensitive to changes in viability, in particular of adult flies, than in fecundity, which may have implications for the management of stable fly populations.

Feeding and breeding aspects of Stomoxys calcitrans (Diptera: Muscidae) under laboratory conditions

Bionomic aspects of Stomoxys calcitrans (Linnaeus, 1758) (Diptera: Muscidae) were studied under laboratory conditions. For this reason, laboratory-rearing techniques were optimized at the National Veterinary School of Toulouse. The colony was maintained at 25±2°C, 50±10% RH under a 12-hour light cycle and observed daily. The size of each adult cage is 30x30x30 cm and designed to house about 500-1,000 flies. The average cycle from egg to adult was 19.2±1.7 days. The mean longevity of imagos was 9.3±5.8 days and not significantly different between sexes. Stable flies were split into two groups; the first was fed with blood, honey and water, and the second was fed only with honey and water. The mean weight of a blood meal was 11.1±3.8 mg with no significant differences between males and females. The mean longevity of non-blood fed flies was found to be significantly higher (10.4±3.9 days) than those fed with blood. The maximum lifespan was shorter for non-blood fed males (17 days) and females (18 days) than for those fed with blood (females: 24 days, males: 23 days). Under these laboratory conditions, S. calcitrans rearing was successfully established. In the end, the number of expected generations of S. calcitrans and the net reproduction rate were estimated to be 11.8 generations/year and 16.2 living females per female respectively.

Spatio-temporal variation of biting flies, Stomoxys spp. (Diptera: Muscidae), along a man-made disturbance gradient, from primary forest to the city of Makokou (North-East, Gabon)

Understanding the pattern of abundance of vector populations is important to control the potential of transmission of associated pathogens. The pattern of abundance of Stomoxys Geoffroy, an ubiquitous blood-sucking fly, is poorly known in tropical Africa. In this study, we investigated the spatio-temporal pattern of abundance of the Stomoxys genus along a gradient of man-made disturbance in north-eastern Gabon. Three sites (one in primary forest, one in secondary forest and one in a man-made environment) were monitored during 13 months using Vavoua traps. Seven species and subspecies were found to live in sympatry, but with distinct patterns of abundance with respect to space and time. The most abundant species was Stomoxys transvittatus Villeneuve, whereas the rarest species was S. xanthomelas Roubaud. Stomoxys calcitrans Linné was preferentially found in man-made environments, whereas S. xanthomelas was preferentially found in primary forest. Stomoxys abundance was the greatest in secondary forest, then in man-made environments and finally in primary forest. A seasonal variation in Stomoxys abundance was also found. In conclusion, forest degradation and deforestation are likely both to favour the concentration of populations of Stomoxys, and to change the specific composition of the Stomoxys community.

Global population structure of the stable fly (Stomoxys calcitrans) inferred by mitochondrial and nuclear sequence data

Stomoxys calcitrans (Diptera: Muscidae: Stomoxyini), a synanthropic fly with a worldwide distribution, is recognized to have an important medical and veterinary impact. We conducted a phylogeographic analysis based on several populations from five major zoogeographic regions of the world in order to analyse population genetic structure of S. calcitrans and to trace its global dispersion. Results from mitochondrial (COI, Cyt-b and ND1-16S) and nuclear (ITS2) DNA show a substantial differentiation of Oriental populations (first lineage) from the Afrotropical, Palearctic, Nearctic, Neotropical and Oceanian populations (second lineage). The divergence time analyses suggest the separation between the two lineages approximately in mid-Pleistocene. Oriental populations are isolated and would not have participated in the colonization of other regions, unlike the Afrotropical one which seems to be the source of S. calcitrans dispersion towards other regions. Demographic analyses indicate that Oriental, Afrotropical and Palearctic regions have undergone a population expansion during late Pleistocene-early Holocene. The expansion time of this cosmopolitan species could have been influenced by continental human expansions and by animal domestication.

Relationships between chemical properties of larval media and development of two Stomoxys species (Diptera: Muscidae) from Reunion Island

The development of two cattle pests, Stomoxys calcitrans L. and Stomoxys niger niger Macquart (Diptera: Muscidae), was studied in the laboratory using seven potential larval media from a dairy farm on Reunion Island. The media were six types of cattle feed and an old manure medium. Egg-to-adult survival, duration of development, and adult live weight at emergence were determined for both fly species on each medium. The media were analyzed for pH, nitrogen, organic matter, and structural compounds (cellulose, hemicellulose, lignin). For S. calcitrans, immature survival was significantly higher on sugarcane leaves, Rhodes grass, and elephant grass; for S. niger, survival was significantly higher on the same substrates plus sugarcane tops. These substrates were characterized by slightly acid pH values (range, 5.4-6.0). In both species, there were significant bell-shape relationships between immature survival and substrate pH. The developmental time of both fly species was significantly shorter on Rhodes grass, Rhodes grass hay, and elephant grass. These substrates were characterized by high cellulose contents and low soluble organic fractions. In both species, there were significant linear relationships between developmental time and cellulose content of substrates. Similarly, there were significant linear relationships between adult live weight and cellulose content of substrates. The C:N ratio of the most favorable substrates was highly variable. Although the relationships revealed in this study do not establish causation, it is suggested that pH and cellulose content may have direct and indirect effects on Stomoxys development.

Effects of temperature on the rate of increase of Stomoxys calcitrans and Stomoxys niger niger (Diptera: Muscidae) from La Réunion island

Adult survival and reproduction were compared between two Stomoxys species that co-occur in La Reunion, the cosmopolitan Stomoxys calcitrans (L.), and the tropical Stomoxys niger niger Macquart. In a first experiment, mean longevity and fecundity were determined at five constant temperatures from 15 to 35 degrees C, after development at the same temperatures. Adult longevity was greatest at 20 degrees C in S. calcitrans and at 15 degrees C in S. niger. Adult S. niger survived longer than adult S. calcitrans, especially at 15 degrees C. At 35 degrees C, all flies died within 3 d. Reproduction occurred only within the 20-30 degrees C range, and S. niger laid more eggs than S. calcitrans. In both species, lifetime fecundity tended to decrease when temperature increased, because of the shortening of the oviposition period. In a second experiment, adults were maintained at 15 degrees C after development at 25 degrees C. The higher temperature during development significantly increased adult longevity in S. calcitrans but not in S. niger. Reproduction occurred at 15 degrees C, with notable fecundity in S. calcitrans (22 eggs per female) but not in S. niger (<1 egg per female). Using previous results on immature survival and developmental time in the two species, several life history parameters were compared at each temperature. Generation time decreased with increasing temperature and was highly similar in both species. Concurrently, the intrinsic rate of increase (r) increased with temperature from 15 to 30 degrees C. At 15 degrees C, r was higher in S. calcitrans, but within the 20-30 degrees C range, r was higher in S. niger. The results suggest 1) S. niger has evolved a strategy of survival without any reproduction during the tropical winter, in contrast with S. calcitrans that breeds more continuously; and 2) S. niger may outnumber S. calcitrans in warm areas, at least when development occurs in media of poor quality.