Heritable variation in the attraction of Drosophila melanogaster to fruit in the field

Drosophila melanogaster were released at a field site and captured with two types of fruit pulp. When flies were rereleased they were more likely to be captured with the same type of fruit on which they were initially captured. Progeny reared in the laboratory tended to be attracted to the same type of fruit as their parents in field tests with two fruit combinations (lemon-orange, lemon-apple) but not a third combination (apple-orange). However, lines selected in the laboratory for increased attraction to apples or oranges over 15 generations differed in their response to these fruit types in the field. This indicates heritable variation for attraction to natural resources under field conditions. Simulations suggest that genotypes differed substantially in their responses to fruit resources.     

Prey preference and egg production of the carabid beetleAgonum dorsale

In order to elucidate whether the aphidRhopalosiphum padi is low quality food for the carabid beetleAgonum dorsale, as it has previously been found to be for cereal spiders, we performed a series of experiments using fruit fliesDrosophila melanogaster as a standard alternative prey (‘control prey’): 1) Prey preference, 2) Aphid consumption for satiated and starved beetles, 3) Egg production on different diets and 4) Preference experiments with fruit flies coated with a taste of different prey types. Other alternative prey types used were earthworms and sciarid midges, all potential prey in the field.A. dorsale has a low preference for aphids compared to fruit flies. Apparently there is an upper limit to the consumption of aphids independent of hunger and much below the beetles' total food demand. Egg production on a pure diet of aphids is lower than on a pure diet of fruit flies; it is extremely low on a pure diet of earthworms; the highest fecundity is found on a mixed diet. As fruit flies coated with a taste of aphids or sciarid midges are less prefered than flies covered with a taste of fruit flies there may be a chemical factor, acting through taste, involved in determining prey preference.     

Search duration ofDrosophila melanogaster on Homogeneous sucrose patches: Relative effects of starvation period,sucrose concentration and patch size

Search duration of adultDrosophila melanogaster on homogeneous sucrose patches increased with the period that flies were starved, the concentration of sucrose which they ingested, and the size of a patch onto which they were released. Since in all conditions the sucrose concentration tested in patch experiments was above the taste threshold, the results indicate that a fly has a set of rules for specifying search duration that integrates external information (resource quality and size) and internal information (period of starvation).     

The use of visual information by house flies,Musca domestica (Diptera: Muscidae), foraging in resource patches

Summary House flies, Musca domestica, respond to visual contrasts on the substrate if a resource is associated with the contrasting patterns. Visible resource patch boundaries serve as a signal to flies that they are about to leave a rewarding patch. Searching flies respond to such visual information by walking along the resource patch boundary and turning back into the patch at its edge. This edge detection and response serve as a mechanism for flies with visual cues to stay in a rewarding patch and locate more resources within it. The intensity of their response correlates with the quality of the resource. In the absence of visual cues, patch shape affects foraging success; flies find more resources in circular than in linear resource distributions. The effects of visual cues, however, render patch shape unimportant. Various substrate contrasts are effective as resource information for flies: dark (e.g., green) figures on bright (e.g., white) backgrounds or bright figures on dark backgrounds. Responses to substrate contrasts measured in this study indicate that, over the short term, house flies can learn a visual cue associated with a food source.     

The fly factor phenomenon is mediated by interkingdom signaling between bacterial symbionts and their blow fly hosts

We tested the recent hypothesis that the"fly factor"phenomenon(food cur-rently or previously fed on by flies attracts more flies than the same type of food kept inccessible to flies)is mediated by bacterial symbionts deposited with feees or regur-gitated by feeding flies.We allowed laboratory-reared black blow flies,Phormia regina(Meigen),to feed and de fecate on bacterial Luria-Bertani medium solidified with agar,and isolated seven morphologically distinct bacterial colonies.We identified these us-ing matrix-assisted laser desorption/ionization mass spectrometry and sequencing of the 165 rRNA gene.In two-choice laboratory experiments,traps baited with cultures of Pro-teus mirabilis Hauser,Morganella morganii subsp.sibonii Jensen,or Serratia marcescens Bizio,captured significantly more flies than corresponding control jars baited with tryptic soy agar only.A mixture of seven bacterial strains as a trap bait was more attractive to flies than a single bacterial isolate(M.m.siboni).In a field experiment,traps baited with agar cultures of P:mirabilis and M.m siboni in combination captured significantly more flies than lraps baited with either bacterial isolate alone or the agar control.As evident by gas chromatography-mass spectrometry,the odor profiles of bacterial isolates differ,which may explain the additive effect of bacteria to the attractiveness of bacterial trap baits.As"generalist bacteria,"P mirabilis and M.m.sibonii growing on animal protein(beef liver)or plant protein(tofu)are similarly effective in attracting flies.Bacteria-derived airborne semiochemicals appear to mediate foraging by flies and to inform their feeding and oviposition decisions.     

The evolutionary history of Drosophila buzzatii XXVII

The correlation between body size and longevity was tested in an Argentinian natural population of Drosophila buzzatii. Mean thorax length of flies newly emerging from rotting cladodes of Opuntia vulgaris was significantly smaller than that of two samples of flies caught at baits. The present results which might be interpreted as directional selection for longevity favoring larger flies are in agreement with previous results achieved in a Spanish natural population of D. buzzatii. Flies emerging from different substrates showed significant differences in thorax length, suggesting that an important fraction of phenotypic variance can be attributed to environmental variability. However, laboratory and field work in different populations of D. buzzatii showed a significant genetic component for thorax length variation.     

Effect of starvation on copulatory activity of Ercolania nigra (Lemche, 1935) (Mollusca,Opisthobranchia, Ascoglossa)

Feeding dominates copulatory behavior in the few opisthobranchs for which behavioral hierarchies have been established. However, the influence of starvation on the dominant role has not been investigated previously. The present study investigates copulatory activity in the ascoglossan opisthobranch Ercolania nigra (Lemche) subject to varying starvation regimes. Copulatory activity of E. nigra is significantly higher in unstarved animals than in animals starved for 2h, 6h, and 24h. The decrease in copulatory activity is independent of the duration of previous starvation within the range tested (2–24 h). Copulatory behavior dominates feeding behavior in 60–80% of the cases, regardless of the duration of previous starvation. Thus the behavioral hierarchy of E. nigra differs markedly from that of the opisthobranchs previously investigated.     

Not berry hungry? Discovering the hidden food sources of a small fruit specialist,Drosophila suzukii

1. Although polyphagy is widespread among Drosophila, some specialist species have evolved in response to resource competition and other selection factors favouring niche separation. The small fruit specialist Drosophila suzukii Matsumura has evolved a unique serrated ovipositor that allows it to access ripening fruit, a niche unavailable to most Drosophila. However, it is unclear whether ancestral traits (the use of non‐fruit resources) are maintained in this specialist species. 2. In this study, maternal preferences and offspring fitness in response to novel apple, mushroom, and bird manure‐based diets were investigated by comparing oviposition and offspring survival and development on various diets. The effect of those diets on survival at cool temperatures and the effect of natal environment/previous exposure on adult preferences were evaluated. 3. Female D. suzukii accepted non‐fruit diets such as mushroom and bird manure, and offspring completed their larval development on all diets tested. However, D. suzukii did not perform well on diets that included bird manure. By contrast, combinational apple/mushroom diets were associated with greater oviposition, lower mortality, faster development, and larger offspring than other diets. These diets were also associated with increased resistance to cold stress, and preference for these diets was positively affected by previous feeding experience. 4. These data suggest that D. suzukii may use non‐fruit resources when preferred resources are scarce. Given that this pest is adapted to temperate climates, alternative resources might provide seasonal nutritional support when fruit resources are not temporally available, although field data are needed to support this hypothesis.     

Development of granular boric acid sugar baits for house flies (Diptera: Muscidae)

Freeze-dried, granular sugar baits containing boric acid as the toxicant were evaluated against house flies, Musca domestica L., in two bioassays with toxicant dose ranges of 3, 5, 7, 8, and 12%, and 3, 5, 9, 17, and 33% boric acid, respectively, calculated and expressed on a dry weight basis. Flies in bioassay 1 were mixed sex and unstarved and flies in bioassay 2 were females only and starved 4 h before testing began. LC50s were 8.97 and 14.33%, and LT50s were 59.75 and 53.34 h in bioassays 1 and 2, respectively. Baits were tested at concentrations as high as 33%, however there was no indication of repellency as seen previously with liquid baits. Reasons for lack of repellency and potential uses for baits are discussed. Development of efficacious granular baits would allow the presentation of higher levels of boric acid in volumes much smaller than required for liquid baits.     

Resource limitation of tephritid flies on lesser burdock,Arctium minus (Hill) Bernh. (Compositae)

Summary The intensity of resource exploitation by phytophagous insects is usually considered to reflect population size. For populations of two flowerhead-attacking tephritid flies, however, the resources utilised were not related to the numbers of searching adults. Tephritis bardanae Schrank attacked 11–13% of the total flowerheads each year, and Cerajocera tussilaginis (Fab) 17–65%, despite much wider and uncorrelated variation in adult numbers. Analysis of field data showed that the proportion of flowerheads used was not limited by poor flowerhead quality, but was restricted by (1) the synchronisation of adult activity with the appearance of flowerheads at the correct age for oviposition, and (2) by factors which influenced the ability of female flies to locate available heads. These restrictions were more severe in T. bardanae and explained its relatively low rate of infestation. Both tephritids tended to avoid flowerheads in open areas. The processes governing resource exploitation in each tephritid operated independently of the other, and a partial separation of the two species between flowerhead types and habitats arose simply because of their different timing of attack.     

Field comparison of chemical attractants and traps for Caribbean fruit fly (Diptera: Tephritidae) in Florida citrus

Field studies in citrus were conducted to compare the following as attractants for the Caribbean fruit fly, Anastrepha suspensa (Loew): torula yeast-borax; propylene glycol (10%); a two-component lure consisting of ammonium acetate and putrescine; a two-component lure consisting of ammonium bicarbonate and putrescine; and a three-component lure consisting of ammonium bicarbonate, methylamine hydrochloride, and putrescine. Various combinations of these attractants in glass McPhail, plastic McPhail-type (Multi-Lure), and sticky panel traps were investigated in two replicated studies. In one study on wild flies, the most effective and least complex trap-lure combination tested was the Multi-Lure with propylene glycol baited with ammonium acetate and putrescine. This trap-lure combination captured significantly more female and male flies than the standard glass McPhail baited with torula yeast-borax in water. All of the trap-lure combinations were female biased, with an overall average of 80.8% (SEM 1.4) flies captured being female. A second study on laboratory-reared, irradiated flies indicated no significant differences among these trap-lure combinations with respect to number of flies recaptured, although rankings based on mean number of flies recovered per trap per day supported results of the first study. The percentage of flies recaptured that were female (83.0%, SEM 0.9) was statistically the same as in the first study. Weekly percentage recovery of flies during the second study was low, possibly due to our fly release strategy. Future release/recovery studies with laboratory-reared flies would benefit from some basic research on release strategies by using different trap densities and on relating recapture rates of laboratory-reared flies (nonsterile and sterile) to capture rates of wild flies.     

Using elemental profiling to determine intrinsic markers to track the dispersal of Prostephanus truncatus,a pest of stored grain with alternative natural hosts

Detecting sources of insects attacking grain stores can help to develop more effective pest management tools. This study considers combinations of chemical elements as intrinsic markers for tracing resource use by Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), a pest of stored maize (Zea mays L., Poaceae) which occurs in natural environments where alternative hosts may support reservoirs of infestation. Prostephanus truncatus were laboratory‐reared on maize or field‐caught in pheromone‐baited flight‐traps. Beetles and hosts were screened for multiple elements using inductively coupled plasma atomic emission spectrometry (ICP‐AES). For elements above detection limits, we tested relationships between determinations for various host plants, and for beetles according to environment where captured. An alternative host, Spondias purpurea L. (Anacardiaceae), contained more Al, B, Ca, Cu, Fe, Mg, Si, and Sr than maize, and less P and Zn. Elemental profiles of beetles were associated with environment, with significantly lower Al, Ca, Cu, Cr, Fe, P, S, Si, Sr, Ti, and Zn determinations in maize‐reared beetles than in beetles captured in agricultural or natural environments. Additionally, Al, Ba, K, P, Sr, and Ti determinations of field beetles captured in agricultural vs. natural environments were significantly different. This suggests Al, Sr, and Ti as candidate markers for environment, and possibly others as elemental concentrations (except B, Ba, Ni, and P) were significantly different in comparisons of all field‐collected vs. maize‐reared beetles. We present a robust practical solution which successfully identified combinations of elemental markers for remotely tracing resource use and dispersal by P. truncatus. We discuss the application of chemical characterisation for identifying intrinsic markers of pests, particularly species with alternative hosts. We discuss how to manage the low replication and unbalanced sample sizes inherent in insect elemental screening, particularly when rarer elements are potential markers.     

Investigating thermal acclimation effects before and after a cold shock in Drosophila melanogaster using behavioural assays

Acclimation to environmental change can impose both costs and benefits to organisms. In this study we explored to what extent locomotor behaviour of Drosophila melanogaster is influenced by developmental temperature and adult temperature in both the laboratory and the field. Following development at 15, 25, or 31 °C, adult flies were tested for locomotor activity at all developmental temperatures in the laboratory before and after exposure to a cold shock and in the field for their ability to locate resources after a cold shock. Both test (15, 25, and 31 °C) and developmental temperatures strongly affected locomoter activity, with flies developed at 25 °C having the highest activity at all three test temperatures before the cold shock. After the cold shock flies developed at 15 °C had higher activity compared with flies developed at 25 and 31 °C when tested at 15 and 25 °C, and flies developed at 25 °C had the highest activity when tested at 31 °C. Furthermore, flies developed at 31 °C showed longer recovery times following the cold shock at test temperatures of 15 and 25 °C. However, flies acclimated at 15 °C during development did not recover faster at 15 and 25 °C compared with flies developed at 25 °C. There were no significant correlations between recovery time and locomotor activity at any of the test temperatures. Flies developed at 15 °C and exposed to a cold shock before release in the field were much more successful in locating a resource at low field temperatures compared with flies developed at 25 and 31 °C. Our results provide support for both the beneficial acclimation hypothesis and the optimal developmental temperature hypothesis, but the results are highly context dependent and change with the temperature experienced by the individual during its lifetime.     

Toxicity of baited spinosad formulations to Ceratitis capitata: from the laboratory to the application

GF‐120, a fruit fly bait designed to attract and kill adult fruit flies, was tested in the laboratory and outdoors to determine effects of pre‐treatment diet and bait aging on mortality of Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae). Two spinosad‐based compounds, GF‐120 and Tracer^® Ultra, had generated two distinctive dose–mortality responds, with LC⁸⁰, LC⁹⁰, and LC⁹⁹ values of 2.4, 2.8, and 4.1 p.p.m., and 255, 479, and 1 143 p.p.m., respectively. The residues of GF‐120 drops, after feeding to the flies, generated 14.3% mortality. The droplet size of the baited spray plays an important role. The toxicity of large drops lasted more than that of small droplets. In the field, exposure to the sun further deteriorates the compound, which lost 50% of its toxicity within 6 days. Disappearance of the compound in the field, due to consumption by various insects, also played a role as 50% of the GF‐120 drops disappeared within 7 days. As mortality was directly related to the amount of insecticide eaten, the effect of GF‐120 depended on the feeding status of the flies: well‐fed flies were almost unaffected compared with starved ones.     

Longevity and pheromone output in stored-product Bostrichidae

Information on longevity and on the effect of ageing on pheromone signalling in Bostrichidae infesting stored products is important because pheromones play a crucial role in mediating aggregation by the species in storages. The longevity of starved and unstarved Prostephanus truncatus (Horn) and Rhyzopertha dominica (Fabricius) were determined at 28+/-1 degrees C, 65+/-2% RH and L12:D12 cycle. Additionally, the effects of ageing on rate of pheromone emission were investigated in R. dominica by comparing emission rates of the aggregation pheromones Dominicalure-1 (DL1) and Dominicalure-2 (DL2) released by adult males ranging from 4, 8, 12, 24 and 48 weeks of age. Mean survival time of starved male and female P. truncatus was 8.6+/-0.6 and 9.1+/-0.4 days, respectively. Starved R. dominica males lived for 5.7+/-0.2 days, and females for 4.7+/-0.1 days. However, mean survival times were not significantly different for starved males vs. females of either species. Mean survival time of unstarved male and female P. truncatus was 27.5+/-2.0 and 18.0+/-3.3 weeks, respectively, and for unstarved male and female R. dominica was 26.1+/-2.8 and 16.7+/-2.9 weeks, respectively. Difference in mean survival times of unstarved males vs. females in both P. truncatus and R. dominica were significant. Between species, no significant difference was observed in mean survival time between unstarved males of P. truncatus or R. dominica, nor between females of both species. Rate of pheromone emission in R. dominica was higher when the insects were relatively young (4, 8 and 12 weeks old), but declined by almost 55% in treatments where the insect were at about 24 or 48 weeks old, suggesting that recruitment potential of R. dominica might reduce substantially as the insects age.     

Evaluation of yellow rectangle traps coated with hot melt pressure sensitive adhesive and sticky gel against Rhagoletis indifferens (Diptera: Tephritidae)

Sticky yellow rectangle traps have been used for many years to capture Rhagoletis (Diptera: Tephritidae) fruit flies. Traditional sticky yellow traps are coated with a sticky gel (SG) that can leave residues on the hands of users. An alternative to SG on traps are hot melt pressure sensitive adhesives (HMPSAs), which are less messy. The main objective here was to evaluate two rectangle traps of two yellow colors, the Alpha Scents Yellow Card coated with HMPSA (Alpha Scents, West Linn, OR), and the Pherocon AM trap coated with SG (Pherocon; Trécé, Adair, OK), for capturing western cherry fruit fly, Rhagoletis indifferens Curran. Flies captured on both traps and held in the laboratory and field did not escape their surfaces. Flies caught on HMPSA were damaged when removed from traps without citrus solvent, whereas flies caught on SG could be removed intact without solvent. In field tests, Alpha Scents traps baited with an ammonium bicarbonate lure captured 1.4-2.2 times more R. indifferens than Pherocon traps baited with the same lure. Results of an experiment that eliminated differences in surface sticky material type, overall size, and surface sticky area between Alpha Scents and Pherocon traps suggested, although did not show conclusively, that more flies were caught on the Alpha Scents than Pherocon traps because of their different yellow color and/or lower fluorescence and not the HMPSA. Overall, the Alpha Scents trap is a viable alternative to the Pherocon trap for detecting R. indifferens.     

Effect of glucose starvation on germ-tube production byCandida albicans

By incubating starved and unstarved yeast cells in synthetic media with a pH of 4.5 or 6.7 at 37°C the effect of a 3 hours' glucose starvation on germ-tube production byCandida albicans was evaluated. In addition the endocellular content of total carbohydrates, glycogen, trehalose and proteins after and before the starvation were dosed. The most interesting result was the overcoming of the pH-regulated dimorphism, thanks to the starvation treatment. Infact the starved cultures produced germtubes indifferently in neutral or acid media, whereas the filamentation of the unstarved cultures was more copious in pH 6.7 medium. The endocellular content of trehalose and protein was unchanged, whereas total carbohydrates and glycogen showed a shortage after the 3 hours' glucose starvation. The possible involvements of these metabolic changes in the regulation of dimorphic transition are discussed.     

Evaluating biological control of fire ants using phorid flies: effects on competitive interactions

The effects of the parasitic phorid fly, Pseudacteon tricuspis Borgmeier, on the competitive interactions between the red imported fire ant, Solenopsis invicta Buren, and a native North American ant, Forelius pruinosus (Roger), were investigated in the laboratory. P. tricuspis is a highly host-specific endoparasitoid of S. invicta workers that is currently being reared and released as a biological control agent of S. invicta in the US. We tested the effect of P. tricuspis on the colony growth rate of S. invicta when S. invicta was forced to compete with F. pruinosus for a protein resource (freeze-killed crickets) in laboratory competition arenas. In addition to colony growth rate, we quantified the effect of the phorid flies on the foraging rate of S. invicta. Though S. invicta significantly reduced its foraging rate in the presence of the phorid flies, we did not detect an effect of the flies on colony growth rate. Possible explanations for these results include behavioral compensation by S. invicta for the presence of the flies. We present these laboratory results in light of a literature search indicating that laboratory tests of biological control agent efficacy are good predictors of field efficacy. We conclude that P. tricuspis alone is unlikely to suppress S. invicta populations in the field by reducing their competitive ability.     

Quantification of Locomotion and the Effect of Food Deprivation on Locomotor Activity in Drosophila

A new method to quantify locomotor behavior in Drosophila is presented, and compared with previous methods. It is based upon a radar wave, reflected by moving flies. A problem associated with the new apparatus is that its output is dependent on fly size. However, for the case the weight of the experimental flies has been determined, a correction is proposed. The method has been used by studying the effect of starvation upon locomotion in Drosophila melanogaster. It was found that starved flies are much more active than well fed flies. The importance of this effect under several conditions is discussed.     

ECOLOGICAL ORIGIN OF MORPHOLOGICAL DIVERSITY: A STUDY OF ALTERNATIVE TROPHIC PHENOTYPES IN LARVAL SALAMANDERS

The role of ecological factors in promoting morphological diversity within and among species is an area of debate among evolutionary biologists. Using morphological differences between sympatric species as evidence that competition promotes divergence (e.g., character displacement), has, in particular, drawn harsh criticism because morphological differences may have evolved during allopatry. In contrast to species, alternative phenotypes within a species have a common phylogenetic history, so differences between phenotypes are likely to result from ecological conditions experienced in sympatry. Using cannibal and typical larval phenotypes of the Arizona tiger salamander, Ambystoma tigrinum nebulosum, we tested two predictions of the hypothesis that resource competition promotes morphological divergence: (1) larval phenotypes should reduce competition by using different resources; and (2) the advantage to developing the alternative, cannibal phenotype should be highest when competition among typical larvae is most intense. We used field surveys and a field experiment to test these predictions. The two larval phenotypes used different resources, especially when competition was intense. The advantage to individual larvae of becoming cannibals was highest when competition for resources among typical larvae was high. These results support the hypothesis that resource competition can promote morphological divergence.