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Across species, animals have diverse sex determination pathways, each consisting of a hierarchical cascade of genes and its associated regulatory mechanism. Houseflies have a distinctive polymorphic sex determination system in which a dominant male determiner, the M-factor, can reside on any of the chromosomes. We identified a gene, Musca domestica male determiner (Mdmd), as the M-factor. Mdmd originated from a duplication of the spliceosomal factor gene CWC22 (nucampholin). Targeted Mdmd disruption results in complete sex reversal to fertile females because of a shift from male to female expression of the downstream genes transformer and doublesex. The presence of Mdmd on different chromosomes indicates that Mdmd translocated to different genomic sites. Thus, an instructive signal in sex determination can arise by duplication and neofunctionalization of an essential splicing regulator.

Granular fly baits remain one of the most popular and effective forms of chemical control of house flies ( Musca domestica ). While these baits contain a sucrose phagostimulant, some also contain the bittering agent denatonium benzoate at 20 or 100 ppm, as a feeding deterrent for humans. The response of adult house flies to 10, 100 and, 1000 ppm denatonium benzoate in sucrose solution was compared to response to sucrose only solution using proboscis extension response and no-choice consumption assays. Three house fly strains, DBQB, WD, and UF, each from a different Florida dairy farm, were tested within two generations of collection. Strain DBQB, but not strains WD or UF, had a known history of exposure to toxic baits containing denatonium benzoate, although recent insecticide history was unknown. For males, all strains avoided proboscis extension response and consumption with 1000 ppm, but not with 10 ppm. Males of WD and UF strains, but not DBQB strain showed significantly lower frequency of proboscis extension response at 100 ppm. Males of WD strain, but not DBQB or UF strains, also avoided consuming 100 ppm. For females, the pattern of significance for proboscis extension response was the same for all strains: avoidance for 1000 ppm but not for 10 or 100 ppm. Female consumption was significantly reduced at 1000 ppm for the DBQB and WD strains, but not for the UF strain, but no strain avoided 10 or 100 ppm for consumption. Thus, our results suggest that in some populations of house flies, 100 ppm of denatonium benzoate may reduce consumption by males, although not consumption by females.

The housefly ( Musca domestica L.) lives in close association with its microbiota and its symbionts are suggested to have pivotal roles in processes such as metabolism and immune response, but it is unclear how the profound physiological changes during ontogeny affect the housefly’s associated microbiota and their metabolic capabilities. The present study applies 16S rRNA gene amplicon sequencing to investigate the development of the host-associated microbiota during ontogeny. The potential for microbiota transfer between developmental stages, and the metabolic potential of these microbiota were evaluated. Representatives of Firmicutes were observed as early colonisers during the larval stages, followed by colonisation by organisms affiliating with Proteobacteria and Bacteroidetes as the flies matured into adults. Microbiota observed across all the developmental stages included Lactococcus , Lactobacillus and Enterococcus , while Weissella and Chishuiella were associated with newly hatched larvae and adults, respectively. Predictive metabolic profiling of the identified microorganisms further suggested that the microbiota and their functional profile mature alongside their host and putative host-microbe relationships are established at different stages of development. The predicted metabolic capability of the microbiota developed from primarily simple processes including carbohydrate and nucleotide metabolisms, to more complex metabolic pathways including amino acid metabolisms and processes related to signal transduction.

The house fly, Musca domestica , is a major mechanical vector of several pathogens, posing significant public health risks. Due to the hazards associated with indoor use of synthetic insecticides, biopesticides offer an eco-friendly alternative. Clove ( Syzygium aromaticum ) flower bud extract contains bioactive insecticidal compounds; however, a comprehensive study of its sublethal effects on M. domestica , along with the associated molecular responses, was lacking. Ethanol-based clove extracts were characterized using gas chromatography–mass spectrometry (GC-MS). This study assessed the lethal and transgenerational effects of clove extract on two generations using age-stage, two-sex life table analysis. Gene expression analysis was conducted on three key stress-responsive genes ( CYP12A2 , CYP6D2 , CYP6A24 ) and one fecundity-related gene, vitellogenin - I ( Vg-I ). GC-MS analysis identified eugenol (68.80%), caryophyllene (13.24%), and acetyl eugenol (13.56%) as the major constituents. The lethal concentrations were determined as LC 5  = 0.405%, LC 5  = 1.574%, and LC 50  = 4.046%. The LC 50 treatment significantly reduced longevity, fecundity, and survival. Mean generation time ( T ) was significantly shorter in the LC 50 group (16.43 days) than in the control (19.89 days). Similarly, key population parameters—intrinsic rate of increase ( r ), finite rate of increase ( λ ), and net reproductive rate ( R 0 )—were reduced. Gene expression studies revealed elevated stress responses and reproductive suppression. The detoxification genes ( CYP12A2 , CYP6D2 , CYP6A24 ) were upregulated, while the fecundity-related gene Vg-I was downregulated. Molecular docking suggested strong binding affinity of caryophyllene to survival-related proteins. These findings suggest that clove extract significantly affects M. domestica , highlighting the potential of caryophyllene as an insecticidal compound.

Background The activation of the immune system by pathogens imposes significant energetic costs on hosts, which may result in the diversion of resources away from other non-essential biological processes, such as growth and reproduction. The underlying mechanisms of trade-offs between immune responses and host fitness remain poorly understood. Results We used a Musca domestica mutant (pirk-KO) to evaluate the influence of non-infection-induced immune system activation on female reproduction and larval growth. Pirk, a negative feedback inhibitor of the immune deficiency (Imd) pathway expressed in intestine and fat body, was induced by bacteria. pirk loss enhanced the immune response of house flies, reflected in sustained upregulated antimicrobial peptide gene expression and improved resistance to bacterial infections. The phenotypic traits of pirk-KO house flies, including delayed larval growth, reduced the body weight, and impaired female fertility, were indicative of the adaptive costs associated with aberrant immune activation. The transcriptional heterogeneities between pirk-KO and wild-type (WT) male flies indicated the overactivation of the Imd signaling pathway, accompanied by significant metabolic adaptations to the loss of pirk. The upregulation of pivotal genes involved in glycolysis and the TCA cycle indicated an enhanced central carbon metabolism in pirk-KO. The downregulation of multiple key enzymes involved in the pentose phosphate pathway in pirk-KO flies suggests a reduction in metabolic flux through the pentose phosphate pathway, which in turn results in impaired anabolism. The collective findings indicate that the pirk-KO flies undergo metabolic reprogramming to increase ATP production as a response to excessive immune activation, rather than incorporating nutrients into cellular biomass for cell proliferation. The pirk-KO flies exhibited a significantly elevated food intake and elevated levels of free glucose, trehalose, and fructose in comparison to the WT flies. Nevertheless, the glycogen and triglyceride contents in the pirk-KO flies were observed to be slightly diminished in comparison to the WT group. Conclusions When the immune defense is activated, the flies extract more free energy to fuel the immunological deployment by increasing nutrient intake, as well as reducing resource allocation to non-essential life-history traits, primarily reproduction and growth.

The house fly, Musca domestica L. is an important pest of livestock and humans, especially in subtropical and tropical regions worldwide. Efficacy of indoxacarb has been shown against a wide range of insects, including M. domestica . This study evaluated the impact of three concentrations of indoxacarb (LC 10 , LC 30 and LC 50 ) on the population and biological parameters of a M. domestica strain. Results showed that pre-adult development was prolonged in the treated population with maximum duration observed in LC 50 treated population (13.88 days). Longevity of male and female M. domestica was the lowest in the LC 50 treated population (23.06 and 25.14 days, respectively). The pre-oviposition period (APOP) was maximum in the LC 50 treated population (3.71 days) while the value of total pre-oviposition period (TPOP) was the highest in the LC 30 treated population (21.12 days). The adults exposed to the LC 50 value of indoxacarb had reduced fecundity (42.00), net reproductive rate ( R o = 5.88), mean generation time ( T  = 21.66) and finite rate of increase ( λ  = 1.09). Similarly, age-specific maternity, age stage specific survival rate, age-stage reproductive values and age-stage life expectancy were higher in LC 10 and LC 30 treatments, while their values were lower in population that was treated with the LC 50 value of indoxacarb. The findings suggested that sub-lethal concentrations (LC 10 , LC 30 ) of indoxacarb had a hormetic effects, while the higher concentration (LC 50 ) had a non-hormetic effect on the biology of M. domestica .

Insecticide resistance in pest populations is an increasing problem in both urban and rural settings caused by over-application of insecticides and lack of rotation among chemical classes. The house fly (Musca domestica L.) is a cosmopolitan fly species implicated in the transmission of numerous pathogens, and which can be extremely pestiferous when present in high numbers. The evolution of insecticide resistance has long been documented in house flies, with resistance reported to all major insecticide classes. House fly resistance to imidacloprid, the most widely used neonicotinoid insecticide available for fly control, has been selected for in field populations through both physiological and behavioral resistance mechanisms. In the current study, house flies collected from a southern California dairy were selectively bred for behavioral resistance to imidacloprid, without increasing the physiological resistance profile of the selected flies. Flies were also successfully selected for behavioral susceptibility to imidacloprid. The rapid selection for either behavioral resistance or behavioral susceptibility suggests that inheritable alleles conferring behavioral resistance were already present in the wild-type fly population collected from the dairy site. The methods used for the specific selection of behavioral resistance (or susceptibility) in the fly population will be useful for further studies on the specific mechanisms conferring this resistance. House fly behavioral resistance was further investigated using behavioral observation and feeding preference assays, with resistance determined to be both contact-dependent and specific to the insecticide (imidacloprid) rather than to a non-insecticidal component of a bait matrix as previously documented.

The housefly, Musca domestica, is an excellent model system to study the diversification of the pathway that specifies the sexual fate. A number of different mechanisms have been described in the housefly, which reflects in part the broad diversity of sex-determining strategies used in insects. In this study we present the molecular identification and characterization of F, which acts as the master switch in the housefly pathway. We provide evidence that F corresponds to the transformer ortholog in Musca (Mdtra), which, as a result of alternative processing, expresses functional products only in individuals committed to the female fate. We demonstrate that, once activated, a self-sustaining feedback loop will maintain the female-promoting functions of Mdtra. Absence of Mdtra transcripts in eggs of Arrhenogenic (Ag) mutant females suggests that maternally deployed Mdtra activity initiates this self-sustaining loop in the zygote. When an M factor is paternally transmitted to the zygote, the establishment of the loop is prevented at an early stage before cellularization and splicing of Mdtra shifts irreversibly to the male nonproductive mode. On the basis of the analysis of two mutant alleles we can explain the different sex-determining systems in the housefly largely as deviations at the level of Mdtra regulation. This plasticity in the housefly pathway may provide a suitable framework to understand the evolution of sex-determining mechanisms in other insect species. For instance, while sex determination in a close relative, the tsetse fly Glossina morsitans, differs at the level of the instructive signal, we find that its tra ortholog, Gmtra, is regulated in a mode similar to that of Mdtra.

Musca flies (Diptera: Muscidae) have been found culpable in the mechanical transmission of several infectious agents, including viruses, bacteria, protozoans, and helminths, particularly in low-income settings in tropical regions. In large numbers, these flies can negatively impact the health of communities and their livestock through the transmission of pathogens. In some parts of the world, Musca sorbens is of particular importance because it has been linked with the transmission of trachoma, a leading cause of preventable and irreversible blindness or visual impairment caused by Chlamydia trachomatis, but the contribution these flies make to trachoma transmission has not been quantified and even less is known for other pathogens. Current tools for control and monitoring of house flies remain fairly rudimentary and have focused on the use of environmental management, insecticides, traps, and sticky papers. Given that the behaviors of flies are triggered by chemical cues from their environment, monitoring approaches may be improved by focusing on those activities that are associated with nuisance behaviors or with potential pathogen transmission, and there are opportunities to improve fly control by exploiting behaviors toward semiochemicals that act as attractants or repellents. We review current knowledge on the odor and visual cues that affect the behavior of M. sorbens and Musca domestica, with the aim of better understanding how these can be exploited to support disease monitoring and guide the development of more effective control strategies.

Abstract Adult house flies (Musca domestica L.) are often a major pest at livestock facilities, where oviposition occurs on decomposing organic matter, such as manure. Some potential foods that adult house flies might consume on dairy farms were examined. Relative to when they were given water alone, survival of males and females was greater when they were given water along with liquid whole milk, formulated calf feed, or corn silage, or finely milled sorghum or soy, or buckwheat inflorescences. However, survival was significantly lower with these foods than with sucrose, although not significantly so for males with milk. There was little to no survival advantage when flies were given water along with milled hominy, wet spent brewers grain, or manure than with water alone. Both males and females spent significant time with their labellum in contact with corn silage, dandelion inflorescences, and buckwheat inflorescences, but little time with their labellum contacting manure or white clover inflorescences. Egg production was not increased by access to water along with buckwheat inflorescences or corn silage relative to sucrose; but egg production was increased by access to liquid whole milk. Reaching mature vitellogenesis stages was improved by prior exposure to water and sucrose solution along with a mixture of dry sucrose, milk, and yolk, or along with calf manure or formulated calf feed, but not with milled soy, sorghum, or hominy, or with wet spent brewers grain or citrus pellets. The diet including sucrose–milk–yolk resulted in the most females reaching mature vitellogenesis stages.