Absence of female-specific protein in the hemolymph of stable fly Stomoxys calcitrans (L.) (Diptera: Muscidae)

Changes, during the reproductive cycle, in fat body, hemolymph, and ovarian proteins of the stable fly Stomoxys calcitrans were characterized quantitatively and qualitatively using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Protein content of all three tissues increased after blood feeding. Fat body protein increased first, followed by hemolymph and ovarian proteins. SDS-PAGE failed to identify vitellogenin in both female hemolymph and fat body samples. No single protein or group of proteins predominated at any stage of the reproductive cycle. Comparisons between male and female stable fly hemolymph and fat body proteins failed to detect female-specific proteins. Female-specific proteins, however, were detected in the hemolymph of four other species of Diptera.     

Diversity of Stomoxys spp. (Diptera: Muscidae) and diurnal variations of activity of Stomoxys indicus and S. calcitrans in a farm, in Wang Nam Khiao District, Nakhon Ratchasima Province, Thailand

A study of species diversity of Stomoxys spp. and diurnal variations of activity of the most abundant was performed during a one year period at a local dairy cattle farm in Wang Nam Khiao District, Nakhon Ratchasima Province, Thailand. Four species of stomoxyine flies were morphologically identified, including Stomoxys indicus Picard 1908, S. calcitrans (Linnaeus 1758), S. sitiens Rondani 1873 and S. uruma Shinonaga and Kanao 1966. The most common species were S. indicus (50.2%) and S. calcitrans (49.5%). S. sitiens and S. uruma were found in small proportions (< 1%). The number of flies captured was significantly different among the three seasons with the greatest number in the rainy season (mean = 66%; df = 2, P < 0.05). The variations of diurnal activity were observed during different period of times (06:00 to 18:00) during three seasons. Both sexes of S. indicus and males of S. calcitrans showed unimodal activity pattern in cool and summer seasons. But a bimodal activity pattern was recorded in rainy season. For females S. calcitrans, a unimodal peak of activity was observed in cool season and a constant variation of activity all along the day in summer and rainy seasons, with an increase from the morning to the evening. A better understanding of stomoxyine fly behavior, especially the daily flight activity, can assist in prioritization and design of appropriate vector prevention and control strategies.     

Microsatellite DNA markers for the Stable Fly,Stomoxys calcitrans (Diptera: Muscidae)

Eight polymorphic microsatellite markers have been isolated from a microsatellite‐enriched DNA library from the Stable Fly, Stomoxys calcitrans. These loci exhibited four to 15 alleles per locus and an expected heterozygosity ranging from 0.19 to 0.84 in the three populations studied from La Réunion island (Indian Ocean). They should therefore be valuable for studying genetic diversity and population structure. Cross‐species amplification of these eight loci in the closely allied species Stomoxys niger niger was successful for four of these loci, one of which was monomorphic and one of which strongly departed from Hardy–Weinberg expectations.     

Twenty-three new microsatellite loci in the stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae)

The stable fly, Stomoxys calcitrans (L.), is a significant pest of cattle. Twenty-three microsatellite markers were isolated from a repeat-enriched genomic library of S. calcitrans. We characterized variation at these markers and found that 17 loci were polymorphic in two fly populations from Florida. Two to nine alleles were observed among the variable microsatellite loci and expected heterozygosities ranged from 0.03704 to 0.85115. These markers will be useful for characterizing population genetic differentiation and for tracking the migration patterns of stable flies in the USA and worldwide.     

Effect of entomopathogenic fungi upon adults of Stomoxys calcitrans and Musca domestica (Diptera: Muscidae)

The pathogenicity and virulence of 10 isolates of entomopathogenic fungi from the soil of lodging pens of dairy production units in Aguascalientes, Mexico, on adults of Stomoxys calcitrans and Musca domestica were determined. All isolates were pathogenic when exposed by aspersion to a concentration of 1×10⁸ conidia/ml, causing between 20.3 and 91.7% mortality in S. calcitrans and between 31 and 91.7% in M. domestica at 7 days post-exposure; in S. calcitrans isolates of Beauveria bassiana (Bb114) and Metarhizium anisopliae (Ma135), sensu lato, were the most noteworthy as mortality reached above 90% with an LC₅₀ of 3.5×10⁵ conidia/ml for Bb114, while for Ma135 reached 1.6×10⁴ conidia/ml. In M. domestica Ma134 and Ma135 showed mortality above 90% with an LC₅₀ of 4.3×10⁴ and 1.4×10⁵ conidia/ml, respectively.     

Microsatellite loci in the stable fly,Stomoxys niger niger (Diptera: Muscidae) on La Réunion Island

Six polymorphic microsatellite markers have been isolated from a microsatellite‐enriched DNA library from the stable fly, Stomoxys niger niger. These loci exhibited five to 10 alleles per locus and an expected heterozygosity ranging from 0.57 to 0.81 in the studied populations from La Réunion Island (Indian Ocean). They should therefore be useful for the study of genetic diversity and population structure of S. niger. In addition, cross‐species amplification of four of these six loci in the closely allied species Stomoxys calcitrans produced interpretable results, two of which would be useful for population biology studies.     

Allozyme variation in stable flies (Diptera: Muscidae)

Polyacrylamide gel electrophoresis was used to resolve allozymes in the cosmopolitan blood-feeding stable fly,Stomoxys calcitrans (L.). Nineteen of 38 loci were polymorphic (53%). Mean heterozygosities among all loci and among only polymorphic loci were 0.096 and 0.182, respectively. These gene diversity measures are about half those among other muscid Diptera. Variation in gene frequencies was examined in 10 natural stable fly populations from Iowa and Minnesota. Gene frequencies were homogeneous at five of eight loci among six populations in 1990 and eight of eight loci among four populations in 1992. Wright'sF statistics showed no significant departure from random mating among stable flies. It was concluded that gene flow compensates for any local differentiation in stable fly populations.     

Characterization of mannosyl transferases during the pupal instar of Stomoxys calcitrans (L)

Particulate fractions (10,000g) from pupae of Stomoxys calcitrans transfer [¹⁴C]-mannose from GDP-[¹⁴C]-mannose to dolichol monophosphate and proteins. Production of the mannosyl lipid was inhibited by Mn²⁺, UDP, GMP, GDP, and EDTA. The insect growth regulator diflubenzuron had no effect on mannosyl transferase activity. Dolichol monophosphate and Mg²⁺ stimulated mannosyl transferase activity. The mannosyl lipid product was identified as mannosyl-phosphoryl-dolichol (Man-P-Dol). The apparent K_m and V_max values for the formation of Man-P-Dol using GDP-[¹⁴C]-Man while holding dolichol phosphate constant were 2.4 ± 0.9 μM and 9.4 ± 2.3 pmol Man-P-Dol·min^?1·mg^?1 protein, respectively. The apparent K_m and V_max values using dólichol phosphate while holding GDP-Man constant were 2.2 ± 1.2 μM and 18.5 ± 1.7 pmol Man-P-Dol·min^?1·mg^?1 protein.     

Digestive enzyme secretion in Stomoxys calcitrans (Diptera: Muscidae)

Summary Enzyme assays and morphological and histological studies show that the opaque zone midgut cells of the haematophagous fly Stomoxys calcitrans are responsible for the production of proteolytic digestive enzymes and that these are secreted into the gut lumen via membrane bound vesicles (MBV). The secretory cycle can be summarized as follows; initially the rough endoplasmic reticulum is stacked and the apices of the cells are packed with MBV. This is followed by a period of release characterized first by cytoplasmic extrusions containing high densities of MBV, then by microvesiculation of the microvilli combined with a progressive distribution of rough endoplasmic reticulum and lightening of the cellular cytoplasm. Glycogen appears in the cells at this stage and is gradually lost as the rough endoplasmic reticulum becomes stacked once more and the numbers of MBV build up again. The cycle which occurs regularly and synchronously in the cells of the zone repeats itself many times up to the completion of digestion of the blood meal. The secretory cycle is discussed with reference to activity in other secretory tissues.The author is indebted to the Science Research Council for financial support     

Sensory and behavioural responses of the stable fly Stomoxys calcitrans to rumen volatiles

Analysis of volatiles from rumen digesta by gas chromatography linked antennogram recordings from Stomoxys calcitrans (L) (Diptera: Muscidae) antennal receptor cells revealed about 30 electrophysiologically active constituents, the most important of which is dimethyl trisulphide with a sensory threshold in the femtogram range. The behavioural responses of S. calcitrans to five chemostimulants (dimethyl trisulphide, butanoic acid, p-cresol, oct-1-en-3-ol and skatole) were tested in a wind tunnel where activation and attraction of hungry flies to rumen volatiles were recorded. Dimethyl trisulphide, butanoic acid and p-cresol were found to attract S. calcitrans. This sensitivity to rumen volatile constituents, that also occur in animal wastes used for oviposition by Stomoxys spp., as well as in flowers used by stable flies as sources of nectar is discussed in the context of the behavioural ecology of these flies.     

Larval experience of stable fly,Stomoxys calcitrans Linneaus, 1758 (Diptera: Muscidae) does not influence oviposition preference in gravid females

1. Hopkins' host selection principle (HHSP) proposes that, in holometabolous insects, gravid females prefer to oviposit on their developmental substrate. This hypothesis is widely explored in phytophagous insects, but few studies have considered blood‐feeding insects. In this study, the HHSP was tested using the haematophagous stable fly, Stomoxys calcitrans (Diptera: Muscidae). Using no‐choice and two‐choice tests, the study first sought to demonstrate whether S. calcitrans larvae recognise their rearing substrate. 2. It was found that when a rearing substrate is offered to S. calcitrans larvae singly (no‐choice) or associated with a non‐rearing substrate (two‐choice), they were able to recognise the substrate in which they developed. This ability disappeared when larvae were transferred to another substrate for 5 h. 3. Next, using oviposition bioassays, it was investigated whether information gathered by pre‐imaginal stages during their development can persist into the adult stages after metamorphosis. It was hypothesised that gravid females emerging from clean and uncleaned pupae reared on sheep and camel dung would still prefer to lay on their rearing substrate. The results revealed that gravid females did not prefer to oviposit on their developmental substrate. In addition, failure to recognise and prefer their developmental substrate was found in gravid females that had emerged from puparia that were cleaned as well as those contaminated with sheep dung. 4. It is concluded that S. calcitrans adult preference is not influenced by their offspring's experience. Overall, the HHSP was not supported by our study, suggesting that this principle may not apply to generalist insects characterised by high plasticity in oviposition substrate acceptance.     

Stable fly, Stomoxys calcitrans, mouthpart removal influences stress and anticipatory responses in mice

Abstract Biting fly attack induces a variety of stress and anxiety related changes in the physiology and behaviour of the target animals. Significant reductions in pain, or more appropriately, nociceptive sensitivity (latency of a foot-lifting response to an aversive thermal stimulus), are evident in laboratory mice after a 1 h exposure to stable flies, Stomoxys calcitrans. The role of the various components of biting fly attack in the development of this stress-induced reduction in pain sensitivity (analgesia) is, however, unclear. This study demonstrates that fly-naive mice do not exhibit a stress-induced analgesia when exposed to stable flies whose biting mouthparts have been removed. In contrast, mice that have been previously exposed to intact stable flies exhibit significant analgesia when exposed to flies that are incapable of biting. However, the level of analgesia induced is lower than that elicited by exposure to intact stable flies. Exposure to non-biting house flies, Musca domestica , has no effect on nociceptive sensitivity. It appears that the actual bite of the stable fly is necessary for the induction of analgesia and probably other stress and anxiety associated responses in fly naive mice. However, mice rapidly learn to recognize biting flies and exhibit significant, possibly anticipatory analgesic responses to the mere presence of biting flies.     

Retention and attempted mechanical transmission of Ehrlichia risticii by Stomoxys calcitrans

Abstract. The ability of adult Stomoxys calcitrans (L.) (Diptera: Muscidae) to retain viable Ehrlichia risticii (Rickettsiaceae), the aetiologic agent of Potomac horse fever (PHF), and mechanically transmit the pathogen from citrated bovine blood artificially infected with E.risticii to susceptible mice was studied. Viable E. risticii were found in the digestive tract of S.calcitrans 3h after the flies had engorged to repletion on infected blood; however, no E. risticii were detected in flies ≥2 days after feeding. Subsequently, groups of S.calcitrans were fed for 20 s on infected blood, then fed to repletion on mice 30, 60,130, 180 or 220 min after having feeding interrupted. Mice displayed no clinical signs of PHF and did not produce anti- E. risticii antibodies when assayed 30 days after S. calcitrans had fed. Although S.calcitrans were able to harbour viable E.risticii for at least 3h, transmission of the disease agent to susceptible mice during interrupted feeding was not demonstrated under these experimental conditions.     

Immunohistological localization of serotonin in the CNS and feeding system of the stable fly Stomoxys calcitrans L. (Diptera: Muscidae)

Serotonin, or 5-hydroxytryptamine (5-HT), plays critical roles as a neurotransmitter and neuromodulator that control or modulate many behaviors in insects, such as feeding. Neurons immunoreactive (IR) to 5-HT were detected in the central nervous system (CNS) of the larval and adult stages of the stable fly, Stomoxys calcitrans, using an immunohistological technique. The location and pattern of the 5-HT IR neurons are described and compared for these two different developmental stages. Anatomical features of the fly feeding system were analyzed in third instar larvae and adult flies using a combination of histological and immunohistological techniques. In third instar larvae, the cibarial dilator muscles were observed within the cibarial pump skeleton and innervated by 5-HT IR neurons in nerves arising from the brain. There were four pairs of nerves arising from the frontal surface of the larval brain that innervate the cibarial pump muscles, pharynx, and muscles controlling the mouth hooks. A strong serotoninergic innervation of the anterior stomatogastric system was observed, which suggests 5-HT may play a role in the coordination of different phases of food ingestion by larvae. Similarly, many 5-HT IR neurons were found in both the brain and the thoracico-abdominal ganglia in the adult, some of which innervate the cibarial pump dilator muscles and the stomatogastric muscles. This is tnhe first report describing neuromuscular structures of the stable fly feeding system. The results reported here suggest 5-HT may play a critical role in feeding behaviors of stable fly larvae and adults.     

Characterization of olfactory sensilla of Stomoxys calcitrans and electrophysiological responses to odorant compounds associated with hosts and oviposition media

Stable flies, Stomoxys calcitrans L. (Diptera: Muscidae), are economically important biting flies that have caused billions of dollars in losses in the livestock industry. Field monitoring studies have indicated that olfaction plays an important role in host location. To further our understanding of stable fly olfaction, we examined the antennal morphology of adults using scanning electron microscopy techniques. Four major types of sensillum were found and classified as: (a) basiconic sensilla; (b) trichoid sensilla with three subtypes; (c) clavate sensilla, and (d) coeloconic sensilla. No significant differences between male and female flies in abundances (total numbers) of these sensillum types were observed, except for medium-sized trichoid sensilla. The distinctive pore structures found on the surface of basiconic and clavate sensilla suggest their olfactory functions. No wall pores were found in trichoid and coeloconic sensilla, which suggests that these two types of sensillum may function as mechano-receptors. Details of the distributions of different sensillum types located on the funicle of the fly antenna were also recorded. Electroantennogram results indicated significant antennal responses to host-associated compounds. The importance of stable fly olfaction relative to host and host environment seeking is discussed. This research provides valuable new information that will enhance future developments in integrated stable fly management.     

Revision of the key characters for the Thricops nigrifrons species-group (Diptera, Muscidae)

An analysis of key characters for the separation of Thricops nigrifrons and Thricops longipes (Diptera, Muscidae) is given. A revised key for Thricops nigrifrons and related species, including two species recently described from the Caucasus, is proposed.