Geotactic Behavior Research Articles

High-resolution, high-throughput analysis of Drosophila geotactic behavior.

Drosophila innate response to gravity, geotaxis, has been previously used to assess the impact of aging and disease on motor performance. Despite its rich history, fly geotaxis continues to be largely measured manually and assessed through simplistic metrics. The manual nature of this assay introduces substantial experimental variability while simplistic metrics provide limited analytic insights into the behavior. To address these shortcomings, we have constructed a fully automated, programable apparatus, and developed a multi-object tracking software capable of following sub-second movements of individual flies, thus allowing reproducible, detailed, and quantitative analysis of geotactic behavior. The apparatus triggers and monitors geotaxis of 10 fly cohorts simultaneously, with each cohort consisting of up to 7 flies. The tracking program isolates cohorts and records individual fly coordinate outputs allowing for simultaneous multi-group, multi-fly tracks per experiment, greatly improving throughput and resolution. The algorithm tracks individual flies during the entire run with ~97% accuracy, yielding detailed climbing curve, speed, and movement direction with 1/30 second resolution. Our tracking also allows the construction of multi-variable metrics and the detection of transitory movement phenotypes, such as slips and falls, which have thus far been neglected in geotaxis studies due to limited spatio-temporal resolution. Through a combination of automation and robust tracking, the platform is therefore poised to advance Drosophila geotaxis assay into a comprehensive assessment of locomotor behavior.

Exploring emotional contagion in zebrafish: A virtual-demonstrator study of positive and negative emotions

Emotional contagion, the transmission of emotions within a group, has been extensively studied in mammals but remains largely unexplored in fish. This study aims to investigate whether emotional contagion, specifically in terms of low and high anxiety levels, can be evoked in zebrafish. This freshwater species has been gaining momentum due to its high genetic homology to humans and complex behavioral repertoire, making it well-suited for exploring social behavior. Our hypothesis posits that zebrafish have the ability to transmit positive and negative emotions to one another through visual cues only and that this transmission is robust over time. To test this, we employed a virtual demonstrator fish approach, where videos of zebrafish exhibiting either high or low geotactic behavior were shown to live zebrafish. Geotaxis, the tendency of a fish to spend more time at the bottom of the tank, is a sensitive measure of anxiety, with high geotactic behavior corresponding to high anxiety levels and vice versa. Our findings indicate that the virtual demonstrator successfully transmitted emotional states to the live fish, as evidenced by changes in the time spent at the bottom of the tank, linear acceleration, and fast-turning maneuvers, metrics that quantify anxiety-like behaviors such as geotaxis and erratic movements. Additionally, we conducted a causal analysis using a transfer entropy approach, revealing a significant flow of information from the virtual demonstrator fish to the live fish, indicating the efficacy and potential of this approach in studying emotional contagion. This study provides additional empirical evidence of how visual cues alone from a virtual demonstrator exhibiting high or low anxious behavior can elicit similar behavioral states in bystander fish, highlighting the potential for emotional contagion beyond mammalian and avian models.

Inbreeding-Driven Innate Behavioral Changes in Drosophila melanogaster.

Drosophila melanogaster has long been used to demonstrate the effect of inbreeding, particularly in relation to reproductive fitness and stress tolerance. In comparison, less attention has been given to exploring the influence of inbreeding on the innate behavior of D. melanogaster. In this study, multiple replicates of six different types of crosses were set in pair conformation of the laboratory-maintained wild-type D. melanogaster. This resulted in progeny with six different levels of inbreeding coefficients. Larvae and adult flies of varied inbreeding coefficients were subjected to different behavioral assays. In addition to the expected inbreeding depression in the-egg to-adult viability, noticeable aberrations were observed in the crawling and phototaxis behaviors of larvae. Negative geotactic behavior as well as positive phototactic behavior of the flies were also found to be adversely affected with increasing levels of inbreeding. Interestingly, positively phototactic inbred flies demonstrated improved learning compared to outbred flies, potentially the consequence of purging. Flies with higher levels of inbreeding exhibited a delay in the manifestation of aggression and courtship. In summary, our findings demonstrate that inbreeding influences the innate behaviors in D. melanogaster, which in turn may affect the overall biological fitness of the flies.

Effect of Methanolic Extract of Caryota no Seed on Geotactic Behaviour and Fecundity in Drosophila melanogaster

Aims: To investigate the effect of the methanolic extracts of Caryota no (CN) seeds negative geotaxis, fecundity and acetylcholinesterase (AChE) using Drosophila melanogaster (DM). Study Design: Experimental design.
 Place and Duration: Sample: African Centre of Excellence for Phytomedicine Research and Development, University of Jos, Jos Plateau State Nigeria between June 2018 and February 2019 Methodology: 50 flies were exposed in each vial to the following concentrations: 300 mg, 350 mg, 400 mg, 500 mg and 600 mg of methanolic extracts in 5 replicates for 7 days with daily recording of mortality. Total protein assays were carried out by Randox method from the supernatant from homogenized whole flies. In vivo antioxidant activity study was conducted by measuring level of acetylcholinesterase (AChE) enzyme activity from supernatants of whole fly homogenates using a spectrophotometer at specific wavelengths over a 2 minute duration. The values were derived as part of the total protein value. Negative geotaxis was done by the climbing assay and fecundity was examined by rate of emergence of larva after exposure of the flies to treatment. The statistical difference among test groups was presumed at P < .05.
 Results: The methanolic extract of CN caused nonsignificant (P = .33) decrease in total protein levels compared to the control. There were also nonsignificant decreases in AChE (P = .30) activity, negative geotactic (P = .80) behaviour and nonsignificant increase in fecundity (P = .17) in the methanolic extract-treated flies compared to the controls.
 Conclusion: It can therefore be concluded that the methanolic extract of Caryota no nonsignificantly improved fertitity and reduced negative geotaxis and AChE activity in DM.

Warming can alter host behavior in a similar manner to infection with behavior-manipulating parasites.

Parasites are ecologically ubiquitous and, by modifying the physiology and behavior of their host organisms, act as key regulators of the dynamics and stability of ecosystems. It is, however, as yet unclear how parasitic relationships will act to moderate or accelerate the ecological impacts of global climate change. Here, we explore experimentally how the effects of parasites on both the physiology and behavior of their hosts can be moderated by warming, utilising a well-established aquatic host-parasite model system-the ecologically important amphipod Gammarus duebeni and its acanthocephalan parasite Polymorphus minutus. We show that, while only warming affected measured components of host physiology, parasite infection and warming both supressed predator-avoidance behavior of the host independently, yet in a similar manner. Six degrees of warming altered geotactic behaviors to the same extent as infection with behavior-manipulating parasites. These results indicate a novel mechanism by which parasites impact their ecosystems that could be critical to predicting the ecological impacts of warming. Our findings highlight the need for holistic knowledge of interaction networks, incorporating multiple interaction types and behaviors, to predict the effects of both warming and parasitism on the dynamics and stability of ecosystems.

Probiotics reduce anxiety-related behavior in zebrafish

There is increasing evidence that gut microbiome could have effects on neurological processes and on behavior. In this study we used the novel tank test (NTT) to analyze zebrafish exploring behavior after four months’ supplementation with probiotics with probed antioxidant and anti-inflammatory properties. Results showed that prolonged ingestion of Lactobacillus rhamnosus CECT8361 and Bifidobacterium longum CECT7347 significantly alters the swimming pattern and mean swimming speed in the zebrafish model. After treatment, zebrafish strongly reduced their bottom-dwelling geotactic behavior when placed in a new tank, which could be correlated to a lower state of anxiety.

Deciphering the known unknowns in the behavioural ecology of the intertidal gastropod Littorina littorea

A considerable amount of attention has been devoted to understand the role of chemoreception in the behavioural ecology of gastropods. There is still, however, a limited amount of information related to their sensory ecology and their subsequent ability to navigate through topographically complex landscapes, such as intertidal rocky shores, despite the documented role of substrate spatial structure in the movement rates and directionality of gastropods. Responses to gravity and visual cues have been documented in a range of intertidal gastropods, but often led to contradictory conclusions. We examined the response of the gastropod Littorina littorea, a keystone grazer on most temperate intertidal ecosystems of the northern hemisphere, to substrate slope, topographic discontinuities and light using purpose-designed experimental set-ups under laboratory-controlled conditions. In contrast to previous results, we showed that L. littorea did not exhibit a strict geotactic behaviour. Instead, they were predominantly thigmotactic following an encounter with a topographic discontinuity, and we suggest that the observed seemingly negative geotactic responses are only a by-product of thigmotaxis, i.e. a thigmotactically-induced negative geotactic response. L. littorea also showed a strong preference for dark areas and shapes. Taken together, our results suggest that thigmotaxis and scototaxis are evolutionary advantageous to navigate through topographically complex and thermally stressful environments, and that the behavioural repertoire of gastropod may be much wider than previously thought.

Behavioral evidence for geomagnetic imprinting and transgenerational inheritance in fruit flies

Certain long-distance migratory animals, such as salmon and sea turtles, are thought to imprint on the magnetic field of their natal area and to use this information to help them return as adults. Despite a growing body of indirect support for such imprinting, direct experimental evidence thereof remains elusive. Here, using the fruit fly as a magnetoreceptive model organism, we demonstrate that exposure to a specific geographic magnetic field during a critical period of early development affected responses to a matching magnetic field gradient later in life. Specifically, hungry flies that had imprinted on a specific magnetic field from 1 of 3 widely separated geographic locations responded to the imprinted field, but not other magnetic fields, by moving downward, a geotactic behavior associated with foraging. This same behavior occurred spontaneously in the progeny of the next generation: female progeny moved downward in response to the field on which their parents had imprinted, whereas male progeny did so only in the presence of these females. These results represent experimental evidence that organisms can learn and remember a magnetic field to which they were exposed during a critical period of development. Although the function of the behavior is not known, one possibility is that imprinting on the magnetic field of a natal area assists flies and their offspring in recognizing locations likely to be favorable for foraging and reproduction.

Effects of a host tree on movement and distribution of winter geometrid moths (Lepidoptera): thickness of trunks and branches

Abstract Adult moths from an ecological group of winter geometrid species look for trees where they copulate and females lay eggs. We investigated how tree trunk and lower branch thickness affects the occurrence of females on trunks and branches and how the density of females and tree trunk thickness affects the occurrence of males on trunks. The research was carried out in a xeric thermophilous oak forest in southern Slovakia (Central Europe) in the winter season 2014–2015. The moths were obtained from Quercus pubescens trees by sticky bands. Three autumn species Operophtera brumata, Erannis defoliaria, Alsophila aceraria and four spring species Agriopis leucophaearia, Agriopis marginaria, Apocheima hispidaria, Phigalia pilosaria were recorded. We have found out that females had not exclusively negative geotactic behaviour as they (except for the rare P. pilosaria) occurred also on lower branches. Tree trunk and lower branch thickness had a positive effect on abundance of females of the three most abundant species (A. leucophaearia, O. brumata, E. defoliaria) on trunks and lower branches. Tree trunk thickness had a positive effect on density of the females of A. leucophaearia on trunks but not on O. brumata and E. defoliaria. The abundance of the males of O. brumata, E. defoliaria and A. leucophaearia on trunks was positively affected by tree trunk thickness and the density of their females.

A locomotor assay reveals deficits in heterozygous Parkinson’s disease model and proprioceptive mutants in adult Drosophila

Severe locomotor impairment is a common phenotype of neurodegenerative disorders such as Parkinson's disease (PD). Drosophila models of PD, studied for more than a decade, have helped in understanding the interaction between various genetic factors, such as parkin and PINK1, in this disease. To characterize locomotor behavioral phenotypes for these genes, fly climbing assays have been widely used. While these simple current assays for locomotor defects in Drosophila mutants measure some locomotor phenotypes well, it is possible that detection of subtle changes in behavior is important to understand the manifestation of locomotor disorders. We introduce a climbing behavior assay which provides such fine-scale behavioral data and tests this proposition for the Drosophila model. We use this inexpensive, fully automated assay to quantitatively characterize the climbing behavior at high parametric resolution in 3 contexts. First, we characterize wild-type flies and uncover a hitherto unknown sexual dimorphism in climbing behavior. Second, we study climbing behavior of heterozygous mutants of genes implicated in the fly PD model and reveal previously unreported prominent locomotor defects in some of these heterozygous fly lines. Finally, we study locomotor defects in a homozygous proprioceptory mutation (Trp-γ1 ) known to affect fine motor control in Drosophila Moreover, we identify aberrant geotactic behavior in Trp-γ1 mutants, thereby opening up a finer assay for geotaxis and its genetic basis. Our assay is therefore a cost-effective, general tool for measuring locomotor behaviors of wild-type and mutant flies in fine detail and can reveal subtle motor defects.

Physicochemical characterization of Suvarna Bhasma, its toxicity profiling in rat and behavioural assessment in zebrafish model.

Suvarna Bhasma is a gold-based Ayurved medicine that has a wide range of therapeutic indications like tuberculosis, diabetes mellitus, rheumatoid arthritis and nervous diseases. Suvarna Bhasma is also used in Suvarnaprashana, an Ayurved advocated therapy being practised to improve immunity in children. To augment traditional understanding, here we present an evidence-based study on Suvarna Bhasma regarding its physicochemical properties, toxicity and efficacy. Suvarna Bhasma was characterised by physicochemical characterization techniques such as scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and atomic emission spectroscopy (ICP-AES). Toxicity of Suvarna Bhasma was studied in Holtzman rats with daily oral dose from 3 mg/kg (therapeutic dose, TD) up to 30 mg/kg (10 TD) body weight for 90 days. Behavioural study, such as motor and geotactic behaviour were examined in zebrafish model to find out any sign of neurotoxicity or behavioural changes due to Suvarna Bhasma administration. Suvarna Bhasma has two types of gold particles, large ones (~60 μm) having irregular shapes, and nano-sized spherical particles (starting from ~10 nm), the latter coated with Fe, Si, O, P and Na. XRD study revealed that all the peaks of Suvarna Bhasma match well with pure gold (face centred cube) with crystallites size 45 ± 2.8 nm. In rat studies, some change in biochemical parameters such as urea, creatinine and alanine aminotransferase (ALT) was observed mainly at the higher therapeutic dose; however, those parameters were within the normal range. There were no significant macroscopic as well as microscopic treatment-related alteration observed, in any of the organs and tissues evaluated. In zebrafish behavioural study, the motor parameters of Suvarna Bhasma treated fish showed normal behaviour analogous to the vehicle control group. Interestingly, the geotactic behaviour showed anxiolytic effects of Suvarna Bhasma as evidenced by the time spent in the upper zone, and average swimming height. The anxiolytic effects persisted for more than 30 days after withdrawing the Suvarna Bhasma treatment. Suvarna Bhasma contained spherical gold nanoparticles. It was nontoxic in rat model at the does tested. Suvarna Bhasma has anxiolytic effects in zebrafish behavioural model.

Effect of dietary inclusions of bitter kola seed on geotactic behavior and oxidative stress markers in Drosophila melanogaster.

This study evaluated the effect of dietary inclusions of Garcinia kola (GK) seed on geotactic behavior and some oxidative stress markers in wildߚtype fruit flies (Drosophila melanogaster). Flies were raised on diet supplement with GK seed for 5 days. The negative geotactic behavior of flies which was used to evaluate their locomotor performance was thereafter evaluated. The flies were subsequently homogenized and the reactive oxygen species (ROS) level, acetylcholinesterase (AChE), catalase and glutathioneߚSߚtransferase (GST) activities, as well as nitric oxide (NO) and total thiol contents were assayed. The phytochemical constituents of GK seed were also determined. It was observed that higher dietary inclusions of GK seed reduced the survival rate of D. melanogaster more significantly compared to control flies. Also, higher dietary inclusions of GK seed significantly reduced locomotor performance and AChE activity, while the ROS level was increased compared to the control. Activities of GST and catalase were significantly increased in flies fed diet supplemented with higher GK seed inclusions but their NO content was significantly reduced compared to control. Phytochemical analysis of GK seed revealed abundance of saponin > glycosides > alkaloids > phenols > flavonoids. These results have shown that dietary inclusion of GK seed at higher concentrations reduced survival rate of D. melanogaster and impaired cholinergic system, with elevated activities of some antioxidant enzymes under acute exposure. These observations could be associated with bioactivities of predominant phytochemicals in GK seed such as saponin and glycosides which have been reportedly toxic at high concentration. Therefore, this study suggests that high consumption of GK seed could induce some toxicological effects and moderate consumption is hence recommended.

Adaptive Changes in the Vestibular System of Land Snail to a 30-Day Spaceflight and Readaptation on Return to Earth.

The vestibular system receives a permanent influence from gravity and reflexively controls equilibrium. If we assume gravity has remained constant during the species' evolution, will its sensory system adapt to abrupt loss of that force? We address this question in the land snail Helix lucorum exposed to 30 days of near weightlessness aboard the Bion-M1 satellite, and studied geotactic behavior of postflight snails, differential gene expressions in statocyst transcriptome, and electrophysiological responses of mechanoreceptors to applied tilts. Each approach revealed plastic changes in the snail's vestibular system assumed in response to spaceflight. Absence of light during the mission also affected statocyst physiology, as revealed by comparison to dark-conditioned control groups. Readaptation to normal tilt responses occurred at ~20 h following return to Earth. Despite the permanence of gravity, the snail responded in a compensatory manner to its loss and readapted once gravity was restored.

Highly Efficient Field Emergence Trap for Quantitative Adult Western Corn Rootworm Monitoring

ABSTRACT: The western corn rootworm, Diabrotica virgifera virgifera LeConte, is one of the most deleterious pests of corn worldwide. Severe root injury interferes with the roots` ability to absorb water and nutrients and results in plant lodging and yield losses. After the pupation in the soil, the emerged adults primarily feed on leaves, corn silk, pollen, and kernels on exposed ear tips of corn. An absolute sampling method for adult western corn rootworm was developed exploiting the strong positive phototropic and negative geotactic behaviour of this coleopteran species. The novel developed pyramidal designed emergence trap is characterized by numerous features which facilitate the estimation of western corn rootworm populations in the field: The trap is highly efficient, simple and economical to construct, portable, easy and quick to install, durable and thus nearly maintenance-free. The installation of the trap relies on cutting corn plants at a height of 20 cm. Both the efficacy of recapturing of ten...

Circadian and Geotactic Behaviors: Genetic Pleiotropy in Drosophila Melanogaster.

Data presented in this paper test the hypotheses that Hirsch’s positive geotaxis (Lo) and negative geotaxis (Hi5) strains of Drosophila melanogaster (fruit fly) differ in length of the free-running circadian activity period (tau) as well as adult geotaxis.Several genes have been shown to alter geotaxis in Drosophila. Two of these genes, cryptochrome (cry) and Pigment-dispersing-factor (Pdf) are integral to the function of biological clocks. Pdf plays a crucial role in maintaining free-running circadian periods. The cry gene alters blue-light (<420 nm) phototransduction which affects biological clocks, spatial orientation and taxis relative to gravity, magnetic fields, solar, lunar, and celestial radiation in several species. The cry gene is involved in phase resetting (entrainment) of the circadian clock by blue light (<420 nm).Geotaxis involves spatial orientation, so it might be expected that geotaxis is linked genetically with other forms of spatial orientation. The association between geotaxis and biological clocks is less intuitive. The data and the literature presented here show that genes, physiology and behavioural aspects of geotaxis, biological clocks, magnetosensitivity and other types of spatial orientation, are complex, intriguing and interrelated.

Positive geotactic behaviors induced by geomagnetic field in Drosophila.

BackgroundAppropriate vertical movement is critical for the survival of flying animals. Although negative geotaxis (moving away from Earth) driven by gravity has been extensively studied, much less is understood concerning a static regulatory mechanism for inducing positive geotaxis (moving toward Earth).ResultsUsing Drosophila melanogaster as a model organism, we showed that geomagnetic field (GMF) induces positive geotaxis and antagonizes negative gravitaxis. Remarkably, GMF acts as a sensory cue for an appetite-driven associative learning behavior through the GMF-induced positive geotaxis. This GMF-induced positive geotaxis requires the three geotaxis genes, such as cry, pyx and pdf, and the corresponding neurons residing in Johnston’s organ of the fly’s antennae.ConclusionsThese findings provide a novel concept with the neurogenetic basis on the regulation of vertical movement by GMF in the flying animals.Electronic supplementary materialThe online version of this article (doi:10.1186/s13041-016-0235-1) contains supplementary material, which is available to authorized users.

Swimming behavior of marine cercariae: Effects of gravity and hydrostatic pressure

Many species of marine larvae use exogenous cues, such as gravity and pressure, for orientation and dispersal, but it is unclear if parasitic larvae exhibit comparable geotactic and barokinetic behaviors. Using two species of marine cercariae, Euhaplorchis sp. and Probolocoryphe lanceolata, which utilize the same first intermediate host, the mangrove snail Cerithidea scalariformis, the hypothesis that they use gravity and pressure to position themselves in the water column to increase the probability of contacting their respective second intermediate hosts was tested. In a test chamber under dark laboratory conditions, Euhaplorchis sp. cercariae ascended, and therefore displayed negative geotaxis, increasing the probability of finding their second intermediate host, salt marsh killifish (Fundulus spp.). In contrast, P. lanceoloata cercariae swam downwards towards the bottom of the chamber, and this positive geotactic behavior would place them in a benthic microhabitat consistent with their second intermediate host, fiddler crabs (Uca spp.). In a subsequent experiment testing swimming activity in response to step increases in pressure, no effect of pressure changes over the range tested (0.3–30kPa) was observed for either species. Collectively, these results suggest that while cercariae are unresponsive to changes in pressure, they are able to utilize gravity for orientation, placing them in the preferred microhabitat of the second intermediate host. This finding is consistent with published photobehavioral studies in which Euhaplorchis swam upwards towards light and P. lanceolata swam downward towards the bottom upon light stimulation. These complementary phototactic and geotactic behaviors optimize host contact, and thus completion of their complex life cycle.

Longevity for free? Increased reproduction with limited trade-offs in Drosophila melanogaster selected for increased life span

Selection for increased life span in Drosophila melanogaster has been shown to correlate with decreased early fecundity and increased fecundity later in life. This phenomenon has been ascribed to the existence of trade-offs in which limited resources can be invested in either somatic maintenance or reproduction. In our longevity selection lines, we did not find such a trade-off. Rather, we find that females have similar or higher fecundity throughout life compared to non-selected controls. To determine whether increased longevity affects responses in other traits, we looked at several stress resistance traits (chill coma recovery, heat knockdown, desiccation and starvation), geotactic behaviour, egg-to-adult viability, body size, developmental time as well as metabolic rate. Longevity selected flies were more starvation resistant. However, in females longevity and fecundity were not negatively correlated with the other traits assayed. Males from longevity selected lines were slower at recovering from a chill induced coma and resting metabolic rate increased with age, but did not correlate with life span.

Divergence in behaviour between the European corn borer,Ostrinia nubilalis, and its sibling speciesOstrinia scapulalis: adaptation to human harvesting?

Divergent adaptation to host plant species may be the major mechanism driving speciation and adaptive radiations in phytophagous insects. Host plants can differ intrinsically in a number of attributes, but the role of natural enemies in host plant specialization is often underappreciated. Here, we report behavioural divergence between the European corn borer (ECB, Ostrinia nubilalis) and its sibling species Ostrinia scapulalis, in relation to a major enemy: humans. Harvesting maize imposes selective mortality on Ostrinia larvae: those located above the cut-off line of the stalk face almost certain death. We show that ECB larvae diapause closer to the ground than those of O. scapulalis, which is sympatric but feeds mainly on weeds. The difference in diapause height results from genetically determined differences in geotactic behaviour. ECB larvae descend towards the ground specifically at harvest time, increasing their chances of surviving harvesting by about 50 per cent over O. scapulalis larvae. Natural enemies appear as a major driver of host-plant specialization in this example, stressing the need to consider 'tri-trophic' ecological niches to understand insect diversification. Our results also strongly suggest that geotaxis evolved as a singular instance of behavioural resistance in a major agricultural pest.

Optimal environmental search and scattered orientations during movement of adult rusty grain beetles, Cryptolestes ferrugineus (Stephens), in grain bulks – suggested movement and distribution patterns

An understanding of insect movement and distribution within grain bulks is essential to effectively control insect pests. In this paper, opinions published in the literature and related to random, downward, and bias movements (the tendency to move in non-random directions) of adults of Cryptolestes ferrugineus have been compared and the net displacement of C. ferrugineus adults in stored-grain bulks was calculated. The average net displacement of the adults inside a stored-wheat mass was 0.435 ± 0.229 m/d. The causes of the scattered orientations were analyzed and the following points were suggested: 1) both experimental observations and theoretical analyses did not support the view that adults of C. ferrugineus exhibit a positive geotactic behavior; 2) the downward movement might be caused by adults' drifting; 3) during their bias movements in responding to environmental factors such as temperature gradients, adults did not significantly decrease their random movements; and 4) their dispersal inside granaries might be mainly influenced by their random movement, drift, and scattered orientations. At the individual level, they were always moving toward optimal environmental areas. At the population level, the random movement plus scattered orientations resulted in a diffusion distribution pattern. Comparison between the suggested diffusion pattern and the insect distributions published in the literature in the following areas was conducted: theoretical analyses of insect diffusion, movements and distributions under laboratory conditions, and dispersal in full-size granaries. Results show that the published insect distributions were consistent with the suggested diffusion pattern.