A modification of the Lincoln Index for estimating the population densities of mobile insects

Abstract. 1. To estimate populations of D.oleae in olive groves on Corfu by mark—recapture techniques, McPhail traps had to be used for sampling.
2. The prolonged sampling period (24 h) resulted in a differential loss of marked flies from the area and this biased the population estimates obtained from the standard Lincoln Index.
3. A modification was devised which enabled the rate of loss of marked flies to be calculated and incorporated into the Index as a correction factor.
4. Field comparisons indicated that the modified Index gave more accurate population estimates than the standard Lincoln Index and therefore it may be applicable to other situations when 'instantaneous' sampling of populations is not practicable.     

基于荧光标记的怒江流域桔小实蝇 (Bactrocera dorsalis)的迁移扩散

2005年7月在云南怒江流域地区,以荧光粉作为标记物,采用“标记-释放-回收”方法,对怒江流域桔小实蝇迁移扩散规律进行了研究。以释放点潞江坝为中心,东南西北4个方位设立桔小实蝇回收点,经过7d的回捕,从释放点沿潞江以北至六库沿线共回收到的标记桔小实蝇43头,最远在距释放点以北97km的地方回收到标记桔小实蝇5头。沿怒江在释放点以南,仅在小于29km的范围内回收到标记桔小实蝇17头。释放点东面和西面未能回收到标记桔小实蝇。分析释放点以北各回收点标记桔小实蝇与非标记桔小实蝇的相互关系揭示,非标记桔小实蝇与标记桔小实蝇在空间动态中具有相同的行为模式,由此推论非标记桔小实蝇与标记桔小实蝇可能来自同一种群。分析怒江流域区的自然地理发现,潞江坝桔小实蝇可借助怒江两边高大山脉形成的天然河谷通道,在适宜的气候条件下,在北上气流的携带下,实现由南向北的远距离迁移扩散;同时,由于高大山脉的阻隔,使潞江坝桔小实蝇没能向东西两个方向作远距离扩散迁移。研究首次揭示了在特定峡谷地区桔小实蝇扩散迁移现象,为桔小实蝇迁移扩散研究提供了新鲜实例,为在当地制定切实有效的桔小实蝇防治策略提供了基础信息。     

基于荧光标记的怒江流域桔小实蝇（Bactrocera dorsalis）的迁移扩散

2005年7月在云南怒江流域地区,以荧光粉作为标记物,采用“标记-释放-回收”方法,对怒江流域桔小实蝇迁移扩散规律进行了研究。以释放点潞江坝为中心,东南西北4个方位设立桔小实蝇回收点,经过7d的回捕,从释放点沿潞江以北至六库沿线共回收到的标记桔小实蝇43头,最远在距释放点以北97 km 的地方回收到标记桔小实蝇5头。沿怒江在释放点以南,仅在小于29 km 的范围内回收到标记桔小实蝇17头。释放点东面和西面未能回收到标记桔小实蝇。分析释放点以北各回收点标记桔小实蝇与非标记桔小实蝇的相互关系揭示,非标记桔小实蝇与标记桔小实蝇在空间动态中具有相同的行为模式,由此推论非标记桔小实蝇与标记桔小实蝇可能来自同一种群。分析怒江流域区的自然地理发现,潞江坝桔小实蝇可借助怒江两边高大山脉形成的天然河谷通道,在适宜的气候条件下,在北上气流的携带下,实现由南向北的远距离迁移扩散;同时,由于高大山脉的阻隔,使潞江坝桔小实蝇没能向东西两个方向作远距离扩散迁移。研究首次揭示了在特定峡谷地区桔小实蝇扩散迁移现象,为桔小实蝇迁移扩散研究提供了新鲜实例,为在当地制定切实有效的桔小实蝇防治策略提供了基础信息。     

Movement of Anastrepha fraterculus from native breeding sites into apple orchards in Southern Brazil

We report movements exhibited by adults of Anastrepha fraterculus (Wiedemann) (Diptera: Tephritidae) from patches of native forests into apple orchards in Southern Brazil. Two mark-release-recapture experiments were conducted using wild flies. Released flies behaved as wild unmarked flies, and periods of peak captures of marked adults coincided with those of unmarked ones. In the first experiment (December 94), out of 2154 released adults, 7.1% were recaptured from day 2 through day 20 after release. Captures peaked from day 7–9 after release. Most marked flies (94.7%) were trapped within 200 m of the release point but eight adults (seven females and one male) were captured in traps placed in an apple orchard, 400–800 m from the release point. The vegetation found between forest and orchard consisted of pastures and annual crops. In the second experiment (January 95), a total of 3284 flies was released in an area where native host plants were abundant and located at ca. 900 m from an apple orchard. In all, 37.1% of marked flies were captured, 99.0% of them at a distance of less than 200 m from the release point. Four adults were captured in an apple orchard, 7 to 24 days after release. They may have reached the orchard through a large and continuous area of native forest. Our results unequivocally demonstrate that A. fraterculus adults are able to disperse from native forests where they originate and invade apple orchards, probably foraging for food and oviposition sites.     

Adult mortality and oviposition rates in field and captive populations of the blowfly Lucilia sericata

Abstract.  1. Adult mortality and oviposition rates were determined for populations of the blowfly Lucilia sericata (Meigen) (Diptera: Calliphoridae). This species is of economic importance as the primary agent of sheep myiasis throughout north-western Europe.
2. Populations of marked flies in six, 1 m³, outdoor field cages and unmarked wild flies at two farms in south-west England were studied simultaneously between May and September 1998.
3. In the field, wild female L. sericata were caught and aged using a combination of wing-fray and ovarian dissection techniques. Survivorship analysis gave estimates of mortality of 1.94% (± 0.037) and 2.09% (± 0.044) per day-degree and mean life expectancy of 51.5 and 47.9 day-degrees above a threshold of 11 °C, at the two farms studied. Mean lifetime reproductive output in the field was estimated to be 159.6 and 138.4 eggs per female at the two farms respectively.
4. The survivorship of cohorts of marked female flies in cages was followed by counting the number of dead individuals each day; the mortality rate of these flies was 0.81% per day-degree (± 3.49 × 10⁻⁴%) and the mean life expectancy was 123.1 day-degrees above a threshold of 11 °C. Mortality rate was shown to increase significantly with average ambient temperature and relative humidity lagged for two sample periods (approximately 10 days). Oviposition rate also increased with average temperature but declined with average relative humidity. A best-fit multiple regression model incorporating both ambient temperature and humidity explained 60.5% of the variance in the pattern of oviposition.
5. The differences between the field and cage populations highlight the caution required when extrapolating life-history parameters from artificial to natural habitats.     

Dispersal ability of marked,irradiated olive fruit flies [Bactrocera oleae (Rossi) (Diptera: Tephritidae)] in arid regions

The dispersal of marked, irradiated olive fruit flies originating from a hybrid laboratory strain was studied in an olive groove located in the arid regions of southern Israel. Release–recapture experiments (eight in total) were conducted throughout a period of 5 months (July–December 2008). In each experiment, ca. 5000 flies were released. Recapture of flies was conducted using a grid of 30 yellow sticky traps set in expanding semicircles from the centre of release. Service of traps was conducted 3 and 15 days after the release. Fly quality and adult food type (only sucrose and protein + sucrose) before release was also investigated. Results point at an average dispersal distance of marked, irradiated olive flies of ca. 50 m. Pre‐release adult diet did not affect dispersal ability. Fly recovery averaged ca. 3.5% during summer and ca. 1.5% during autumn. Most of the recovery concentrated during the first 3 days after releases, suggesting low survival of the released flies afterwards. As inferred from circular statistics, direction of dispersal was non‐random with a significant directionality to the north‐west. Results are discussed in view of environmental temperatures and wind direction.     

Genetics of Natural Populations. Xliii. Further Studies on Rates of Dispersal of DROSOPHILA PSEUDOOBSCURA and Its Relatives

The amount of gene flow among local populations of a species is determined by the dispersal capacity of that species. Population samples of Drosophila pseudoobscura, D. persimilis, D. azteca, and D. miranda were collected, marked with ultraviolet fluorescent dusts, and released as soon as possible after capture. One and two days after release, recaptures were made on baits placed at 40-meter intervals in straight lines intersecting the release point. On alternative days, the baits were placed in North-South or in East-West directions. The distribution of the recaptured flies about the release point is very nearly normal. No significant differences between the dispersal rates of the four species are observed; however, males disperse slightly further than females. The variances averaged 50,822 m2 on the first day and 80,048 m2 on the second day and the estimated mean distances from the release point averaged 263 m and 361 m respectively. The genetic implications of the results are discussed.     

Effects of overhead canopy on macroinvertebrate production in a Utah stream

SUMMARY. 1. Macroinvertebrate abundance and production were compared between an open and shaded site of a stream in the Wasatch Mountains, Utah. Mean biomass was significantly higher at the open site for midges (Chironomidae), 4.6×; Baetis bicaudatus , 5.7×; Baetis tricaudatus , 2.3×; Drunella coloradensis , 12× and Cinygmula sp., 1.6×, Abundance of most other macroinvertebrates (except black flies: Simuliidae) was also greater at the open site, but differences were not significant. Black fly biomass was 1.7× greater at the shaded site.
2. Seasonal production, estimated by the size-frequency and instantaneous growth rate methods, was greater at the open site than the shaded site for most taxa (except black flies) and reflected differences in standing crops between the sites rather than differences in rate of growth. Excluding black flies, production at the open site was twice as high as at the shaded site.
3. The greater abundance and production of most invertebrate taxa at the open site is probably associated with either higher quality food (algae and algal detritus), or a phototactic attraction to sunlit areas.
4. Sampling of large cobbles was an efficient method of sampling all taxa except Cinygmula sp. which was more abundant on smaller substrate particles.     

Persistence of sterile screwworm (Diptera: Calliphoridae) flies at a release site.

Studies to determine the persistence of released, sterile screwworms, Cochliomyia hominivorax (Coquerel), were conducted in Belize, Central America, in 1987-1988. A total of nine releases were made, each consisting of 4,000 females marked with a fluorescent dust. Previous similar studies with baited fly traps indicated that flies died or dispersed from the release site within 3-4 d. For this study, flies were recaptured at sentinel animals. Recapture rates varied greatly between releases, a result that was not correlated with any weather parameter. The pattern of recapture indicated a sharp drop in the released population after 9-10 d, with a few flies persisting in the release area for up to 3 wk. The results suggest that survival of released sterile flies is comparable with estimated survival rate and life span of wild, native flies.     

Dynamic information and host acceptance by a tephritid fruit fly

Abstract. 1. Female apple maggot (Rhagoletis pomonella Walsh) flies held in field cages usually oviposited in an unparasitized (non-pheromone marked) fruit when it was encountered.
2. Oviposition in a previously parasitized (pheromone marked) fruit depended upon the time since the last oviposition (TSLO) and the percentage of infested fruit encountered during search for oviposition sites.
3. Previous theories of host acceptance suggest that the acceptance or rejection of a host should depend dichotomously on time since last oviposition and the fraction of marked hosts in the last five encounters. The experiments, however, show considerable variability and are thus not consistent with the theory.
4. A new theory for the experiments is introduced. This model involves physiological (egg complement) and informational state variables and leads to intuitive understanding of the experimental results. In particular, the model shows how the plasticity in oviposition site selection may arise from fitness maximizing behaviour. Alternative models are also discussed. All of the models stress the importance of physiological and informational states.     

Visual and olfactory cue interaction in resource-location by the blowfly, Lucilia sericata

Abstract. The interactions between olfactory and visual cues in the landing responses of the blowfly Lucilia sericata (Meigen) (Diptera: Calliphoridae) were examined in a laboratory wind tunnel. The odour of liver and sodium sulphide solution released at 1 L/min, resulted in a greater number of landings, closer to, but downwind of, the central odour release point, than when odour was absent. Three-day-old protein-deprived females landed in greater numbers than protein-fed female flies of the same age; no difference existed between 6-day-old protein-fed or protein-deprived females. Six-day-old, protein-fed flies landed closer to the odour source than did 3-day-old, protein-fed flies. In the presence of odour, flies landed closer to the central release point when it was accompanied by a visual cue. No such effect of the visual cue was evident in the absence of odour. When a plain white sticky-surface (25 × 25 cm) was paired with an identical white surface plus odour, approximately equal numbers of flies landed when the surfaces were placed together; increasingly higher numbers of flies landed on the surface with the odour cue when the distance between the surfaces was increased. When a white surface with a visual cue was presented with the plain white surface plus odour, more flies landed on the white surface with the visual cue than on the plain white surface with odour when they were close together. However, as these two surfaces were moved apart, flies landed increasingly more on the surface with the odour than the surface with the visual cue. The results show that while odour cues may enhance the induction of landing by female L. sericata , visual cues are important when selecting a final landing site.     

Do Gravid Black Flies (Diptera: Simuliidae) Oviposit at Their Natal Site?

We present information on an aniline dye marking method for black flies. In the laboratory, adults were sprayed with 2% aqueous solutions of four colors of aniline dyes; brilliant blue and methyl orange gave the best results in longevity trials. In field trials we were able to recapture 1.3% of newly emerged marked and released flies at oviposition sites. Mark–release–recapture experiments were designed to distinguish among three competing models concerning oviposition site selection by gravid female black flies: (1) larval site fidelity (“Do flies return to the site that they experienced as larvae?”), (2) adult site fidelity (“Do flies return to the site that they experienced as adults?”), and (3) no site fidelity (“Do flies oviposit at random, i.e., without regard to adult or larval experience?”). Models 1 and 2 were rejected. There is, however, no reason to reject Model 3, the no site fidelity model. Thus, we conclude that for members of the S. venustum/verecundum complex (i.e., S. rostratum, S. venustum, and S. truncatum) females find an “apparently suitable” waterway in which to oviposit; this may or may not be their natal site.     

Characteristics and distribution of opposition sites of the grasshopper Zonocerus variegatus (L.)

Abstract. 1. The dry-season population of Zonocerus in southern Nigeria oviposits in dense aggregations under single or clumped woody plants or on the edge of tall continuous stands of vegetation. No egg pods were found oviposited singly.
2. The vegetation under which oviposition occurs is the most common available at the time of the year. There seems to be no selection of particular species of plants so long as they provide good low shade.
3. Oviposition can take place in a wide range of gravelly soils.
4. Topography is not important as long as the oviposition site is on high ground away from damp areas subject to flooding.
5. There was a mean of 618 pods per oviposition site from forty-one sites which were dug up, and there was a significant correlation between the area of a site and the number of pods.
6. There was a marked tendency for oviposition sites to be found close to cassava. At two localities of approximately 20 ha each 90% of the sites were found within 30 m of cassava.
7. It is suggested that permanent shade is the most important factor in the selection of a site and this is probably related to the survival of the eggs during their 6–7 months development.     

Hygrothermal determinants of insect activity patterns: the Diptera of water-lily leaves

Abstract. 1. The numbers and types of flies resting on water-lily leaves varied through the diurnal cycle. The different patterns of occupancy were recorded in relation to time of day and to microclimatic conditions at the leaf surface.
2. Overall fly activity on the leaves varied according to gross climatic patterns on particular days. The timing of activity differed according to species.
3. Smaller, darker flies (especially ernpids and Notiphila ) were common on the leaves early and late in the day, with the more reflective dolichopodids occurring only towards midday and in full sun. Hence there were clearcut correlations between both the size and reflectance properties of flies, and the climate (in particular radiation received at the leaf surface); though this pattern was superimposed on a diurnal activity effect.
4. The timing of insect activity on the leaves could therefore be related to hygrothermal considerations, particularly the raising and maintenance of body temperature and avoidance of heat stress. Different types of fly used the favourable microclimate around the leaves as a resting site at times appropriate to their own biological requirements.     

The movement and dispersal of Liriomyza trifolii (Diptera: Agromyzidae) in a chrysanthemum greenhouse

Investigation of the dispersal of Liriomyza trifolii in a 1–2 ha chrysanthemum greenhouse indicated that the average distance flown by female flies was greater than that flown by male flies. However, flies of both sexes were found at the furthest distance from the release point (102 m) which indicates that flies in the greenhouse could be considered to be a single inter-breeding population. When the data were fitted to a generalised distance-dispersal model, examination of the parameters revealed density decreased with distance more rapidly for males than females. Also, the model showed that males tended to be slightly more attracted to each other than were females. The applicability of these results to the development of pest management systems for L. trifolii is discussed.     

Horizontal and vertical dispersal of dengue vector mosquitoes, Aedes aegypti and Aedes albopictus, in Singapore

To study the dispersal of dengue vector mosquitoes in Singapore, females of Aedes aegypti (L.) and Aedes albopictus (Skuse) (Diptera: Culicidae) were fed blood containing rubidium (Rb), which was detectable in their eggs by means of Graphite Furnace Atomic Absorption Spectrophotometry (GFAAS). Laboratory calibration of the Rb reading, for a range of egg numbers from Rb-fed females, indicated a reasonably linear relationship and an unequivocal distinction between results with zero and one marked egg. Rb-marked female Aedes mosquitoes aged 3-5 days were released in semi-rural and urbanized parts of Singapore, with an array of ovitraps extending to a radius of 320 m from the release point. Subsequently, Rb-marked Aedes eggs were detected throughout the array, with similar distributions on each of the 4 days after release. More Rb was detected nearer the release point. However, when correction was made for the greater areas of zones further from the release point (and therefore presumably existence of more alternative oviposition sites), there were no significant differences in the numbers of marked eggs per ovitrap in the zones nearer or further from the release points. It is concluded that females of both these Aedes (Stegomyia) species could disperse easily and quickly throughout areas of radius 320 m in search of oviposition sites. This contrasts with the general belief that Ae. aegypti seldom flies more than 50 m and that control operations can safely be based on such an assumption. Releases on level 12 of a 21-storey apartment block, with ovitraps on each storey, showed similar easy and rapid dispersal to the top and bottom of the block.     

Ovipositional behaviour of Simulium argyreatum and S. variegatum and its relationship to infection by the fungus Erynia conica (Entomophthoraceae)

SUMMARY. 1. At two sites in Devon S. argyreatum and S. variegatum only oviposited on water-splashed boulders. The oviposition season was from 15 March to 9 November at Steps Bridge and from 28 March to 7 December at Fingle Bridge. Flies laid eggs only during a brief period after sunset.
2. Flies infected with the fungus E. conica returned to the oviposition sites at the same times as healthy flies, but infected flies appeared to be unable to lay eggs.
3. At least 10.9% of healthy flies were found to have infective conidia of E. conica on their wings after laying eggs.     

Growth and development of larval northern cricket frogs (Acris crepitans) in relation to phytoplankton abundance

SUMMARY. 1. Tadpoles of Acris crepitans were collected from two ponds in central Illinois, Depth, water temperature, distance from shore and water samples were taken at each sample site. The potential for food limitation and non-random habitat selection were examined.
2. Algal densities from water samples averaged over 1.0× 10⁶ cells ml⁻¹ in Scott's pond hut only 4.6×10³ cells ml⁻¹ in Vic's pond.
3. Guts of tadpoles from Scott's pond contained more algal cells than did guts of tadpoles from Vic's pond. Tadpoles from Scott's pond were consistently larger and more advanced in development than tadpoles collected from Vic's pond at the same lime. Therefore, tadpoles of Scott's pond were able to utilize the higher algal densities whereas tadpoles of Vic's pond may be food-limited, causing reduced growth and development.
4. Canonical discriminant analysis was used to test whether sites with different numbers of tadpoles could be distinguished based on environmental variables. Canonical function I was primarily a measure of water depth at a sample site. This function was significant in Scott's pond only. Sites containing one or more tadpoles were not easily distinguished from each other, but were found in consistently shallower water than sites where no tadpoles were found.     

Influence of intertree distance on foraging behaviour of Rhagoletis pomonella in the field

Abstract. 1. We tested a prediction from contemporary foraging theory that animals should decrease their allocation of energy to the searching of individual patches when interpatch travel costs decrease.
2. We used individual Rhagoletis pomonella Walsh (Diptera: Tephritidae) females foraging for oviposition sites (= Crataegus fruit) in a host tree which was surrounded by four other trees at varying distances.
3. We found that flies generally invested less search, measured as time spent searching a tree or number of leaves visited on a tree, when neighbouring trees were nearby than when farther away.
4. Under our test conditions, flies appeared to have difficulty locating neighbouring trees at a distance of more than 1.6 m.
5. Our study calls into question the interpretation of search effort by insects within resource patches in the absence of information on interpatch distances.     

Influence of habitat structure on the phonotactic strategy of a parasitoid fly Emblemasoma auditrix

Abstract.  1. Females of the parasitoid fly Emblemasoma auditrix find their host cicadas ( Okanagana rimosa ) using the acoustic signals produced by the host. The phonotactic behaviour of the parasitoid was studied with regard to differently structured habitats.
2. Habitats were modified experimentally within a distance of 2.5 m (approximately the natural range of phonotaxis) from a loudspeaker broadcasting a model of the host calling song.
3. Video analysis showed that in an open habitat (no landmarks) more than 60% of the flies performed a direct flight towards the loudspeaker.
4. In structured habitats (with one to three landmarks) more than 90% of the flies landed on their way to the acoustic target.
5. In about 50% of the landings flies paused for several seconds indicating re-orientation during that time. Several flies included sequences of walking in their approach behaviour, whereby most walking occurred close to the loudspeaker.
6. In summary, the phonotactic approach and host finding depends on the habitat structure.