A theory of the pattern induced flight orientation of the fly Musca domestica

The theory presented here describes the visual orientation behavior of fixed flying insects (the fly Musca domestica) in the presence of elementary patterns. The theory, which is based on a number of experimental results, Reichardt (1973), is a phenomenological one whose main purpose is to provide an organizational framework for treating a complex phenomenon without the need of detailed assumptions about the neural mechanisms actually involved.A simple hypothesis concerning the basic structure of the pattern fixation process leads to an equivalent stochastic equation of the Langevin type, which can be linearized for simple single-stripe panoramas. A critical experiment supports these theoretical assumptions. In addition, the effect on pattern fixation behavior of adding contrast noise to the background of the panorama, is quantitatively predicted by the theory.In the more general case of a panorama consisting of many vertical stripes, the Fokker-Planck equation associated with the Langevin equation, no longer linear, is solved. Making use of an experimentally proven superposition principle, the stationary pattern fixation behavior of the fly in an arbitrary panorama consisting of a collection of vertical stripes is predicted. In this context, concepts like pseudo-invariance and phase-transition can be applied to the insects orientation behavior. The theory presented here seems to contain rich classification properties, which might provide the foundations for an understanding of more complex pattern discrimination processes.Possible extensions of the theory, as well as some similarities to human eye fixation, are also discussed.     

A theory of the pattern induced flight orientation of the fly Musca domestica II

In a preceding paper, Poggio and Reichardt (1973a), a phenomenological theory describing the visual orientation behaviour of fixed flying flies (Musca domestica) towards elementary patterns was presented. Some of the problems raised in this first paper are treated here in more detail. The mapping between the position dependent torque distribution — D(ψ) characteristics — associated with a given pattern and the stationary orientation distribution p(ψ), is studied taking into account that the fluctuation process (generated by the fly) is coloured gaussian noise. Under certain critical conditions this may lead to an “early symmetry breaking” in the mean values of the p(ψ) distribution. The validity of the “superposition principle” has also been examined. Although shift and superposition give the main qualitative features of the “attractiveness profile” D(ψ), associated with a 2-stripe pattern, superposition does not hold quantitatively for stripe separations up to about 80°. Evidence is presented suggesting that such an effect is due to inhibitory interactions between input channels of the fly's eye. Implications of this finding with respect to the problem of spontaneous pattern preference are also discussed.     

Ecdysteroidostatin from the house fly,Musca domestica

Ovaries from house flies maintained on sucrose secrete large amounts of ecdysteroid when they are cultured with ovarian ecdysteroidogenic hormone, OEH. However, ovarian ecdysteroid secretion is reduced by incubation with both OEH and the ovarian ecdysteroidostatin (OES). A partially purified OES fraction from a semi-preparative reverse phase HPLC C₁₈ column caused a 98% inhibition of ovarian ecdysteroid secretion in vitro at a concentration of 0.8 equivalents per μl. Ovaries can be activated to produce ecdysteroid in vivo by feeding diet containing protein to flies maintained on sucrose. Ecdysteroid secretion was inhibited when the in vivo stimulated ovaries were cultured with OES. This suggests that OES does not interfere with the OEH activation mechanism, but blocks ovarian ecdysteroid synthesis or release. Furthermore, OES inhibition is reversible and ecdysteroid secretion resumes when OES is removed. Musca OES could explain the decrease in ecdysteroid levels found in flies after mid-vitellogenesis. Both adult male and female abdomens contain OES, but OES was not transferred to females during mating. Evidence is presented that OES is not a trypsin modulating oostatic factor. Arch. Insect Biochem. Physiol. 38:166–176, 1998. © 1998 Wiley-Liss, Inc.     

Disease dynamics and persistence of Musca domestica salivary gland hypertrophy virus infections in laboratory house fly (Musca domestica) populations

Past surveys of feral house fly populations have shown that Musca domestica salivary gland hypertrophy virus (MdSGHV) has a worldwide distribution, with an average prevalence varying between 0.5% and 10%. How this adult-specific virus persists in nature is unknown. In the present study, experiments were conducted to examine short-term transmission efficiency and long-term persistence of symptomatic MdSGHV infections in confined house fly populations. Average rates of disease transmission from virus-infected to healthy flies in small populations of 50 or 100 flies ranged from 3% to 24% and did not vary between three tested geographical strains that originated from different continents. Introduction of an initial proportion of 40% infected flies into fly populations did not result in epizootics. Instead, long-term observations demonstrated that MdSGHV infection levels declined over time, resulting in a 10% infection rate after passing through 10 filial generations. In all experiments, induced disease rates were significantly higher in male flies than in female flies and might be explained by male-specific behaviors that increased contact with viremic flies and/or virus-contaminated surfaces.     

Visually induced height orientation of the fly Musca domestica

The visually controlled height orientation of fixed flying flies (Musca domestica) was investigated. The flight lift force measured by a transducer drives the vertical motion of a panorama. The dynamical conditions of the free flight are electronically simulated for the fly with respect to this degree of freedom of motion. In most of the experimentally investigated cases the panorama consists of a horizontally oriented narrow dark stripe on a bright background. The fly orientates with respect to the stripe, transporting it into a stable fixation position just below the equatorial plane of its compound eyes. It is experimentally demonstrated that the formalism of the linearized theory of the pattern induced flight orientation — Poggio and Reichardt (1973a) — can be applied to describe the height orientation of the fly. The experimental evidence concerning the simultaneous perception of stripes moving in a well defined manner in front of each of the two compound eyes is consistent with the hypothesis that the two halves of the visual system are perceptually additive.     

Immature house fly (Musca domestica) control in breeding sites with a new Brevibacillus laterosporus formulation

A bacterial formulation containing spores of a Brevibacillus laterosporus strain from Sardinia, known to be toxic by ingestion to the house fly (Musca domestica), was assayed in laboratory, outdoor, and field conditions for the control of immature stages of this pest. In all laboratory assays, the bacterial formulation exhibited toxicity against house fly larvae. A concentration of 1 x 10(8) spores of B. laterosporus/g of diet caused 100% mortality of house fly immature stages. The same formulation, applied at a concentration of 1 x 10(8) spores/ml, equivalent to a dose of 2 liters/m(2), caused a reduction in adult emergence from laboratory and natural breeding substrates (outdoor cage experiments) up to 80.3 and 57.8%, respectively. Similarly, this formulation applied in the cow pen of a diary farm at a dose of 2 liters/m(2) produced a significant reduction (30%) in immature fly development. Therefore, the use of this bacterial preparation in microbiological control strategies for the integrated pest management of this species is promising.     

Microsatellite loci in the house fly,Musca domestica L. (Diptera: Muscidae)

Genomic libraries from house flies enriched for (CA)₁₅ and (CAG)₁₀ repeats were constructed by using biotinylated probes. Twenty‐five loci were isolated and evaluated for polymorphisms in wild flies representing two geographically diverse populations. Fourteen of 19 dinucleotide loci, and one of six trinucleotide loci were polymorphic. One hundred and twenty‐seven alleles were detected, 39 of which were private. Average number of alleles per polymorphic locus was 8.4 ± 2.5 and average heterozygosity was 72 ± 4%. F_ST by the private allele method was 0.73. Three of 15 loci showed significant heterozygote deficiencies, attributed to null alleles. Five of 15 loci were amplified in the face fly, Musca autumnalis.     

Asymptotic oscillations in the tracking behaviour of the fly Musca domestica

From recent theoretical work (Poggio and Reichardt, 1981), high frequency oscillations are expected in the angular trajectory of houseflies tracking a moving target if the target's retinal position controls the flight torque by means of a stronger optomotor response to progressive than to regressive motion. Experiments designed to test this conjecture have shown that (a) asymptotic non-decaying oscillations are found in the torque of female houseflies tracking targets moving at constant angular velocity; (b) the magnitude of the oscillations grows monotonically with mean retinal excentricity of the target; (c) the period of the oscillation is around 180–200 ms. The experimental findings are consistent with the hypothesis that a progressive-regressive mechanism plays a significant role in the tracking behaviour of female houseflies. From this phenomenological point of view a flicker mechanism that is active only for nonzero motion is equivalent to a progressive-regressive system. The relatively long period of the oscillation requires more complex reaction dynamics than a pure single dead-time delay. As a specific example we show that a model where the reaction to progressive motion is sticky, holding for a longish time after the ending of the stimulus, is consistent with the experimental data.     

Vibrio cholerae laboratory infection of the adult house fly Musca domestica

The present study was designed to test the hypothesis that house flies may be capable of specifically harbouring ingested Vibrio cholerae in their digestive tracts. Flies were continuously fed green fluorescent protein (GFP)‐labelled, non‐O1/non‐O139 environmental strains of V. cholerae. Bacterial burdens were quantitatively measured using plate counts and localization was directly observed using confocal microscopy. Vibrio cholerae were present in the fly alimentary canal after just 4 h, and reached a plateau of ～10⁷ colony‐forming units (CFU)/fly after 5 days in those flies most tolerant of the pathogen. However, individual flies were resistant to the pathogen: one or more flies were found to carry < 180 V. cholerae CFU at each time‐point examined. In flies carrying V. cholerae, the pathogen was predominantly localized to the midgut rather than the rectal space or crop. The proportion of house flies carrying V. cholerae in the midgut was dose‐dependent: the continuous ingestion of a concentrated, freshly prepared dose of V. cholerae increased the likelihood that fluorescent cells would be observed. However, V. cholerae may be a transient inhabitant of the house fly. This work represents the first demonstration that V. cholerae can inhabit the house fly midgut, and provides a platform for future studies of host, pathogen and environmental mediators of the successful colonization of this disease vector.     

Linkage analysis of an acetylcholinesterase gene in the house fly Musca domestica (Diptera: Muscidae)

Linkage of an acetylcholinesterase (AChE) gene was detected in the house fly, Musca domestica L., by using the backcross method between a strain, aabys, that had a morphological multichromosomal marker on each of the five autosomes and a wild strain, LPR. Both strains were homozygous in this gene, and we used eight single nucleotide polymorphisms (SNPs) between them to distinguish the parental sequences in the backcrossed progeny, two of which resulted in the amino acid substitiutions common to the Drosophila and Aedes AChEs insensitive to organophosphates and carbamates. F, appeared to be a wild phenotype, and the AChE gene was heterozyous of aabys and LPR. In the backcross progeny, 32 (2(5)) phenotypes appeared, and 10 phenotypes with one wild or morphological marker were picked up for genotyping by the SNPs of AChE gene. A combination of the morphological markers and the SNPs revealed that the AChE structural gene is linked to autosome 2 in the house fly.     

Electrophoretic analysis of genetic variability in the house fly (Musca domestica L.)

Methods are described for the resolution of house fly, Musca domestica L., enzymes by vertical polyacrylamide gel electrophoresis. An electrophoretic survey in Ames, Iowa, of 51 loci distributed among 26 enzyme systems revealed that 40% of the loci are polymorphic. Observed and expected heterozygosities measured at 33 loci were 0.0981 and 0.1148, respectively. A significant deficiency of heterozygotes was noted at certain loci.Journal Paper No. J-11423 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project No. 2411.     

Symmetrical pattern of follicle arrangement in the ovary of Musca domestica (Insecta,Diptera)

Summary The position of the oocyte nucleus within the ooplasm is fixed during the mid and late stages of house fly oogenesis. The germinal vesicle is located near the border of the nurse chamber, towards the periphery of the oocyte. The position of the anlage of the chorion raphe is strictly related to the germinal vesicle. As the raphe corresponds to the dorsal side of the later embryo, both the position of the oocyte nucleus and the raphe anlage in the follicular epithelium are early indicators of the dorsoventral axis of the house fly egg cell. In cross sections of the ovary the follicles are arranged in several concentric circles. The dorsal sides of all follicles within the ovary are oriented to an imaginary center. This center of orientation lies eccentrically near the medial part of the female abdomen. The resulting symmetrical pattern can be observed throughout the course of oogenesis. This implies that only a few follicles have the same dorsoventral orientation as the mother fly, and therefore this arrangement is contradictory to the imprinting hypotheses of body axis formation as well as to a possible inductive role of gravity.Supported by the Deutsche Forschungsgemeinschaft