Preference Of Flies Research Articles

Nature and nurture in fruit fly hearing.

As for human language learning and birdsong acquisition, fruit flies adjust their auditory perception based on past sound experiences. This phenomenon is known as song preference learning in flies. Recent advancements in omics databases, such as the single-cell transcriptome and brain connectomes, have been integrated into traditional molecular genetics, making the fruit fly an outstanding model for studying the neural basis of "Nature and Nurture" in auditory perception and behaviors. This minireview aims to provide an overview of song preference in flies, including the nature of the phenomenon and its underlying neural mechanisms. Specifically, we focus on the neural circuitry involved in song preference learning, with which auditory experiences shape the song preference of flies. This shaping process depends on an integration hub that processes external sensory stimuli and internal states to enable flexible control of behavior. We also briefly review recent findings on the signals that feed into this integration hub, modulating song preference of flies in an experience-dependent manner.

Larval diet impacts black soldier fly (Diptera: Stratiomyidae) thermal tolerance and preference.

Thermal tolerance and preference are key parameters impacting agricultural production systems. In this study, the impact of larval diet on black soldier fly thermal tolerance and preference across life-stages and sexes was examined. Larvae were fed either a low-protein high-carbohydrate synthetic diet (i.e., P7C35), a high-protein low-carbohydrate synthetic diet (i.e., P35C7), or the Gainesville diet (i.e., C) as a control and reference. Our results demonstrate that the impacts of larval diet on black soldier fly thermal tolerance and preference could be stage and sex specific. The mean heat knockdown temperatures (HKT) ranged between 46.6 and 47.9 °C. Synthetic diets resulted in greater HKT and the difference decreased form larvae (e.g., ∼1 °C) to adults (e.g., ∼0.2 °C). The mean chill-coma recovery time (CCRT) ranged between 8.3 and 21.6 min. Not much differences were detected between diets, but CCRT became longer from larvae to adults. The mean thermal preference ranged between 13.6 and 29.5 °C. Larvae fed synthetic diets preferred much lower temperatures than the control diet. A bimodal distribution was observed for adults regardless of sex. Differences on body mass, lipid, and protein contents were detected among diets; however, more research should be done before any conclusions can be linked to their thermal traits. These findings highlight the importance of considering the ingredients and nutritional makeup of larval diets when optimizing temperature management protocols for mass production of black soldier flies. Conversely, specific diets can be developed to promote survival under extreme rearing temperatures.

Age and calorific restriction impact immature black soldier fly (Diptera: Stratiomyidae) thermal tolerance and preference

Abstract Thermal tolerance and preference are traits commonly considered when mass-producing farmed animals as temperature impacts production. In this study, the impact of age and calorific restriction of immature black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae) on associated thermal tolerance and preference was examined. Both age (7-d-old for young larvae and 14-d-old for old larvae) and calorific restriction (led to size differentiation, small for calorific restriction and large for non-restriction) within a given stage influenced thermal tolerance (i.e. KR50) and thermal preference. Results indicate the interaction between age and calorific restriction was significant on both larval and prepupal thermal tolerance but not thermal preference. Median heat tolerance KR50 ranged from 46.4 °C (large, old prepupae) to 48.4 °C (large, young larvae). Median cold tolerance KR50 ranged from 21.6 °C (small, young larvae) to 32.1 °C (small, old larvae). Young larvae preferred median temperatures ∼3.0 °C greater than old larvae. Large larvae preferred median temperatures ∼2.0 °C lower than small larvae. Results from this study indicate ontogeny (i.e. stage of development) and calorific restriction have significant impacts on black soldier fly thermal tolerance and preference. Precise regulation of temperature in an industrial setting is necessary for optimal batch production of the black soldier fly (e.g. survival) and for colony maintenance (e.g. prepupae producing adults and potentially eggs). The same can be said with regards to maintaining consistent age and calorific restriction of immatures produced within each batch as variation in such traits impacts thermal tolerance and preference (e.g. survival to harvest for producing protein or adults for colony) as well. The methods and temperatures used in this study could serve as a foundation for developing standard operating procedures for regulating temperatures experienced by black soldier fly larvae industrially produced.

Apparent density, trypanosome infection rates and host preference of tsetse flies in the sleeping sickness endemic focus of northwestern Uganda

BackgroundAfrican trypanosomiasis, caused by protozoa of the genus Trypanosoma and transmitted by the tsetse fly, is a serious parasitic disease of humans and animals. Reliable data on the vector distribution, feeding preference and the trypanosome species they carry is pertinent to planning sustainable control strategies.MethodologyWe deployed 109 biconical traps in 10 villages in two districts of northwestern Uganda to obtain information on the apparent density, trypanosome infection status and blood meal sources of tsetse flies. A subset (272) of the collected samples was analyzed for detection of trypanosomes species and sub-species using a nested PCR protocol based on primers amplifying the Internal Transcribed Spacer (ITS) region of ribosomal DNA. 34 blood-engorged adult tsetse midguts were analyzed for blood meal sources by sequencing of the mitochondrial cytochrome c oxidase 1 (COI) and cytochrome b (cytb) genes.ResultsWe captured a total of 622 Glossina fuscipes fuscipes tsetse flies (269 males and 353 females) in the two districts with apparent density (AD) ranging from 0.6 to 3.7 flies/trap/day (FTD). 10.7% (29/272) of the flies were infected with one or more trypanosome species. Infection rate was not significantly associated with district of origin (Generalized linear model (GLM), χ2 = 0.018, P = 0.895, df = 1, n = 272) and sex of the fly (χ2 = 1.723, P = 0.189, df = 1, n = 272). However, trypanosome infection was highly significantly associated with the fly’s age based on wing fray category (χ2 = 22.374, P < 0.001, df = 1, n = 272), being higher among the very old than the young tsetse. Nested PCR revealed several species of trypanosomes: T. vivax (6.62%), T. congolense (2.57%), T. brucei and T. simiae each at 0.73%. Blood meal analyses revealed five principal vertebrate hosts, namely, cattle (Bos taurus), humans (Homo sapiens), Nile monitor lizard (Varanus niloticus), African mud turtle (Pelusios chapini) and the African Savanna elephant (Loxodonta africana).ConclusionWe found an infection rate of 10.8% in the tsetse sampled, with all infections attributed to trypanosome species that are causative agents for AAT. However, more verification of this finding using large-scale passive and active screening of human and tsetse samples should be done. Cattle and humans appear to be the most important tsetse hosts in the region and should be considered in the design of control interventions.

Host preference and Leishmania infantum natural infection of the sand fly Phlebotomus perfiliewi in northern Italy

The host preference of hematophagous insects is important in determining the cycle of pathogens that they potentially transmit; for example, sand flies are competent vectors of Leishmania parasites. In this work, we evaluated the host preference of sand flies collected in the Emilia-Romagna region of Italy in 2018 and 2019 in an area in which Leishmania infantum circulates actively. Out of about 30,000 sampled sand flies, we obtained 252 engorged females, which were processed to identify the sources of blood meals. Sampling data collected confirmed a positive phototropism of Phlebotomus (Ph.) perfiliewi respect to Ph. perniciosus and the enhanced efficiency of light traps in collecting engorged females compared with traps baited with carbon dioxide. We identified blood source in 185 females (183 Ph. perfiliewi, two Ph. pernicious). The most bitten animal was the roe deer (49.5%), followed by humans (29.2%), hare (7.1%) and cow (4.7%). Other animals, including wild boar, horse, donkey, porcupine, chicken and red fox, were less represented (<2%), while the blood of dogs and rodents were not detected. In addition, we singly screened engorged females for Leishmania founding 5 positive specimens, fed on roe deer (4) and man (1), providing evidence of parasite circulation in a sylvatic environment, where presence of dogs was not common. These findings suggest the existence of an uncharacterized Leishmania reservoir in the surveyed area.

Impact of age, size, and sex on adult black soldier fly [Hermetia illucens L. (Diptera: Stratiomyidae)] thermal preference

Population growth and rapid urbanisation have increased the global demand for animal feed and protein sources. Therefore, traditional animal feed production should be increased through the use of alternative nutrient sources. Insects as feed are beginning to fill this need. One such insect is the black soldier fly,Hermetia illucens L. (Diptera: Stratiomyidae). However, to more effectively mass produce the black soldier fly, a better understanding of its thermal biology is needed. Thus, the aim of this study was to evaluate the impact of age, size, and sex on adult black soldier fly thermal preference. The thermal preference of adult black soldier flies was determined by exposing flies to a thermal gradient with a range of surface temperatures and monitoring their positions over time. An aluminium plate was used to create a linear thermal gradient where surface temperatures ranged from ~15-60 °C. Flies were distinguished by age (1-d-post-emergence vs 7-d-post-emergence), size (large vs small) and sex (male vs female) to assess whether thermal preference differed by specific life-history traits. Thermal preference for 7-d-post-emergence adults was significantly lower (19.2 °C) than 1-d-post-emergence adults (28.7 °C), respectively. Similarly, small adults selected significantly cooler (21.1 °C) temperatures than large adults (26.9 °C). No significant differences in thermal preferences were found between sex, regardless of age or size. In fact, males and females had similar thermal preference of 23.8 and 24.2 °C, respectively. This study reveals that multiple life-history traits of adult black soldier fly affect their thermal preference, and thus should be taken into consideration by mass rearing facilities to optimize production.

Potential of parasitoid Gronotoma micromorpha Perkin (Hymenoptera: Eucoilidae) as a biocontrol agent for pea leafminer fly, Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae)

The potential of the parasitoid, Gronotoma micromorpha (Perkin) as a biological control agent for pea leafminer fly, Liriomyza huidobrensis (Blanchard) has been evaluated in a series of studies on the fly preference to host instars, biological characteristic and functional response to the host density. The studies were carried out at the Laboratory of Integrated Pest Management (IPMLab), Faculty of Agriculture Udayana University in Denpasar and Greenhouse Owned-Farmer in Pancasari Buleleng, Bali (1200 m asl; average temperature 23.67 ± 5.69 °C and average RH of 64 ± 17.69%). The results showed that G. micromorpha has a strong preference towards the 3rd instar larvae of L. huidobrensis. The pre-oviposition period was 0.4 ± 0.67d, oviposition was 12.5 ± 2.0d and post-oviposition period was 1 ± 0.0d while the peak oviposition occurred on the 4th day. Meanwhile, all the offsprings produced were females which indicated that parthenogenesis thelytokous was present in G. Micromorpha and the fecundity was 29 ± 3.77 per female adult. Furthermore, the average life span for the adult was 13 ± 1.42 days with an oviposition period of 12.5 ± 2.01 days. The average post-oviposition period was 1 ± 0.0 days and average development period of egg to adult was 32.03 ± 0.98 days. Meanwhile, the breeding potential was high with an average daily percentage of 2.27 ± 0.27 fecundity and a maximum spawning occurred on day 4. The functional response was type-2 and it is the rate at which parasitism increase with increase in population of the host density. Hence, the biological characteristics and mode of functional response by the parasitoid showed its potential as a biological pesticide for pea leafminer L. huidobrensis.

Voluntary intake of psychoactive substances is regulated by the dopamine receptor Dop1R1 in Drosophila

Dysregulated motivation to consume psychoactive substances leads to addictive behaviors that often result in serious health consequences. Understanding the neuronal mechanisms that drive drug consumption is crucial for developing new therapeutic strategies. The fruit fly Drosophila melanogaster offers a unique opportunity to approach this problem with a battery of sophisticated neurogenetic tools available, but how they consume these drugs remains largely unknown. Here, we examined drug self-administration behavior of Drosophila and the underlying neuronal mechanisms. We measured the preference of flies for five different psychoactive substances using a two-choice feeding assay and monitored its long-term changes. We found that flies show acute preference for ethanol and methamphetamine, but not for cocaine, caffeine or morphine. Repeated intake of ethanol, but not methamphetamine, increased over time. Preference for methamphetamine and the long-term escalation of ethanol preference required the dopamine receptor Dop1R1 in the mushroom body. The protein level of Dop1R1 increased after repeated intake of ethanol, but not methamphetamine, which correlates with the acquired preference. Genetic overexpression of Dop1R1 enhanced ethanol preference. These results reveal a striking diversity of response to individual drugs in the fly and the role of dopamine signaling and its plastic changes in controlling voluntary intake of drugs.

Identification of Blood Meal of Sand Flies in a Cutaneous Leishmaniasis Endemic Area, Volta Region-Ghana

<i>Background</i>: Vector incrimination is of utmost importance in the transmission of <i>Leishmania</i> species identified in the Volta region of Ghana. The feeding preference of sand flies provides valuable information about the vector-host interactions, including reservoir host. <i>Objective</i>: The main aim of this study was to identify the blood meal in collected sand flies and its source from three villages in a cutaneous leishmaniasis endemic area in the Ho Municipality. <i>Method</i>: Sand flies was collected using CDC light straps and sticky paper traps from Lume Atsiame, Dodome Dogblome and Dodome Awuiasu. They were morphologically identified by taxonomic keys. DNA was extracted from the individual sand flies using the potassium acetate extraction method. Polymerase chain reaction (PCR) amplification of cytochrome b gene (<i>cyt b</i>) fragment was carried out and subsequently DNA sequenced. <i>Results</i>: Of a total of three hundred and sixty-three (363) female sand flies that were analysed, eighty-four (84) representing 23.14% were positive for blood meal presence with an amplified DNA of the expected size, 359bp. Out of the number that was sequenced, the <i>cyt b</i> sequencing revealed that four (4) blood fed females fed on bloodmeal from human (<i>Homo sapiens</i>) and house mouse (<i>Mus musculus</i>). <i>Conclusion</i>: The blood meal presence was more predominant in <i>Sergentomyia ghesquierei</i> and least in <i>Sergentomyia schwetzi</i>. This may aid in the development of effective strategies to control cutaneous leishmaniasis in the endemic areas.

Transgenerational effects from single larval exposure to azadirachtin on life history and behavior traits of Drosophila melanogaster

Azadirachtin is one of the successful botanical pesticides in agricultural use with a broad-spectrum insecticide activity, but its possible transgenerational effects have not been under much scrutiny. The effects of sublethal doses of azadirachtin on life-table traits and oviposition behaviour of a model organism in toxicological studies, D. melanogaster, were evaluated. The fecundity and oviposition preference of flies surviving to single azadirachtin-treated larvae of parental generation was adversely affected and resulted in the reduction of the number of eggs laid and increased aversion to this compound over two successive generations. In parental generation, early exposure to azadirachtin affects adult’s development by reducing the number of organisms, delay larval and pupal development; male biased sex ratio and induced morphological alterations. Moreover, adult’s survival of the two generations was significantly decreased as compared to the control. Therefore, Single preimaginal azadirachtin treatment can affect flies population dynamics via transgenerational reductions in survival and reproduction capacity as well as reinforcement of oviposition avoidance which can contribute as repellent strategies in integrated pest management programs. The transgenerational effects observed suggest a possible reduction both in application frequency and total amount of pesticide used, would help in reducing both control costs and possible ecotoxicological risks.

Evaluation of host susceptibility, preference and offspring performance of Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae) on different hosts

The melon fruit fly, Zeugodacus cucurbitae (Coquillett) is a quarantine insect pest worldwide and affects the vegetable quality through its direct feeding and indirectly by passing way for secondary pathogens. This study investigated the host susceptibility, preference and offspring performance of Z. cucurbitae under the laboratory conditions. Different vegetable hosts i.e., brinjal (Solanum melongena L.), bitter gourd (Momordica charantia L.), zucchini (Cucurbita pepo L.), bottle gourd (Lagenaria siceraria [Molina] Standley) and cucumber (Cucumis sativus L.) were tested under no choice and free choice tests. Results showed that C. sativus and C. pepo have highest number of visits/host and oviposition puncture/host. C. sativus showed highest pupal recovery and pupal weight in both only choice and free choice test. While, highest percentage of emergence and female off springs were observed in C. pepo under only choice and free choice scenarios. Furthermore, maximum deformities in progeny were observed in case of L. siceraria under both test case scenarios. The current study provides exploratory support that fruit flies respond differently to host species that co-exists in field under choice and no choice test. Further, hosts of advantage to fruit flies are adopted more. The host and choice preference of fruit flies have the influence on the pest management strategies for the vegetable crops.

Commingled black and white cows (Bos taurus; Angus and Charolais) in high-elevation rangeland are differentially parasitised by Haematobia irritans

Globally horn flies (Haematobia irritans) are one of the most economically damaging parasites of beef cattle. These obligate blood-feeding external parasites take blood meals from cattle leading to blood loss, annoyance avoidance behaviours, and reductions in animal performance. Development of chemical resistance by horn flies suggests that novel management strategies are needed. More in-depth understanding of parasitism relative to hide colour and temperature, especially in a changing climate, may enhance animal production. In peak parasitism periods of 2016 and 2017, we measured horn fly loads on commingled black Angus and white Charolais cows in a cold high-elevation rangeland in Wyoming, USA. We tested how breed, year, and interactions explained horn fly parasitism and economic thresholds. In 2016 we also measured ambient and external cow temperatures to further elucidate thermal ecology mechanisms explaining horn fly hide colour preferences. Mean annual horn fly infestations were always four times greater or more on black cows than white cattle both years, but not all cattle reached economic thresholds all years and the breed by year interaction was not significant. Difference in horn fly preference for black cattle over white cattle in our cold high-elevation environment may be explained by greater absolute and relative external surface temperatures of black hided cows. Host colour and thermal preferences of horn flies could be incorporated into integrated pest management strategies that only treat darker hided cattle and producers in cold high-elevation environments conduct real-time monitoring to determine if treatments are even needed on a year-by-year basis.

Communicating the nutritional value of sugar in Drosophila

Sweet-insensitive Drosophila mutants are unable to readily identify sugar. In presence of wild-type (WT) flies, however, these mutant flies demonstrated a marked increase in their preference for nutritive sugar. Real-time recordings of starved WT flies revealed that these flies discharge a drop from their gut end after consuming nutritive sugars, but not nonnutritive sugars. We proposed that the drop may contain a molecule(s) named calorie-induced secreted factor (CIF), which serves as a signal to inform other flies about its nutritional value. Consistent with this, we observed a robust preference of flies for nutritive sugar containing CIF over nutritive sugar without CIF. Feeding appears to be a prerequisite for the release of CIF, given that fed flies did not produce it. Additionally, correlation analyses and pharmacological approaches suggest that the nutritional value, rather than the taste, of the consumed sugar correlates strongly with the amount (or intensity) of the released CIF. We observed that the release of this attractant signal requires the consumption of macronutrients, specifically nutritive sugars and l-enantiomer essential amino acids (l-eAAs), but it is negligibly released when flies are fed nonnutritive sugars, unnatural d-enantiomer essential amino acids (d-eAAs), fatty acids, alcohol, or salts. Finally, CIF (i) is not detected by the olfactory system, (ii) is not influenced by the sex of the fly, and (iii) is not limited to one species of Drosophila.

Olive cultivar and maturation process on the oviposition preference of Bactrocera oleae (Rossi) (Diptera: Tephritidae).

The olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is a key-pest in the main olives producing areas worldwide, and displays distinct preference to different olive cultivars. The present work intended to study oviposition preference towards three Portuguese cultivars (Cobrançosa, Madural, and Verdeal Transmontana) at different maturation indexes. Multiple oviposition bioassays (multiple-choice and no-choice) were conducted to assess cultivar preference. No-choice bioassays were conducted to assess the influence of different maturation indexes (MI 2; MI 3, and MI 4) in single cultivars. The longevity of olive fly adults according to the cultivar in which its larvae developed was also evaluated through survival assays.Cultivar and maturation are crucial aspects in olive fly preference. Field and laboratory assays revealed a preference towards cv. Verdeal Transmontana olives and a lower susceptibility to cv. Cobrançosa olives. A higher preference was observed for olives at MI 2 and MI 3. The slower maturation process in cv. Verdeal Transmontana (still green while the other cultivars are reddish or at black stage) seems to have an attractive effect on olive fly females, thus increasing its infestation levels. Olive fly adults from both sexes live longer if emerged from pupae developed from cv. Verdeal Transmontana fruits and live less if emerged from cv. Cobrançosa. Therefore, olive cultivar and maturation process are crucial aspects in olive fly preference, also influencing the longevity of adults.

Ground ultra low volume (ULV) space spray applications for the control of wild sand fly populations (Psychodidae: Phlebotominae) in Europe

The Phlebotomus sand flies are considered an important vector of both canine and human leishmaniasis. Current measures for sand fly control include mostly indoor interventions, such as residual spraying of dwellings (IRS) to target endophilic sand fly species with very limited number of vector control tools for outdoor interventions against exophilic sand flies. In this study we investigated the efficacy of ground ultra low volume (ULV) space spray applications of a deltamethrin based product against field populations of P. perfiliewi, a major nuisance and pathogen-transmitting sand fly species of the Mediterranean Basin. Sand fly flight activity patterns and flight height preference within candidate treatment sites (kennels) were determined prior to treatments in order to optimize the timing and application parameters of the spray applications. On average there was a distinct activity peak between 20.00–22.00 h for both male and female P. perfiliewi with more than 45% and 30% of the population sampled occurring between 20.00–21.00 h and 21.00–22.00 h, respectively. No significant difference was observed in sand fly numbers from sticky traps placed at 0.5 up to 1.5 m height. However, there was a significant decrease in sand fly numbers at 2 m indicating a preference of sand flies to fly below 2 m. The low and high application rate of deltamethrin resulted in mean sand fly population decrease of 18 and 66%, respectively between pre-and post-treatment trap nights. The percent mean population change in the untreated control area was a positive number (30%) indicating that there was an increase in numbers of sand flies trapped between pre- and post-treatment nights. The results of this study provide strong evidence that ground ULV space spray applications when applied properly can result in significant sand fly control levels, even in a heavily infested sand fly environment such as the kennel sites used in this study.

Natural variation in stochastic photoreceptor specification and color preference in Drosophila.

Each individual perceives the world in a unique way, but little is known about the genetic basis of variation in sensory perception. In the fly eye, the random mosaic of color-detecting R7 photoreceptor subtypes is determined by stochastic on/off expression of the transcription factor Spineless (Ss). In a genome-wide association study, we identified a naturally occurring insertion in a regulatory DNA element in ss that lowers the ratio of SsON to SsOFF cells. This change in photoreceptor fates shifts the innate color preference of flies from green to blue. The genetic variant increases the binding affinity for Klumpfuss (Klu), a zinc finger transcriptional repressor that regulates ss expression. Klu is expressed at intermediate levels to determine the normal ratio of SsON to SsOFF cells. Thus, binding site affinity and transcription factor levels are finely tuned to regulate stochastic expression, setting the ratio of alternative fates and ultimately determining color preference.

Gut Microbiota Modifies Olfactory-Guided Microbial Preferences and Foraging Decisions in Drosophila

The gut microbiota affects a wide spectrum of host physiological traits, including development [1-5], germline [6], immunity [7-9], nutrition [4, 10, 11], and longevity [12, 13]. Association with microbes also influences fitness-related behaviors such as mating [14] and social interactions [15, 16]. Although the gut microbiota is evidently important for host wellbeing, how hosts become associated with particular assemblages of microbes from the environment remains unclear. Here, we present evidence that the gut microbiota can modify microbial and nutritional preferences of Drosophila melanogaster. By experimentally manipulating the gut microbiota of flies subjected to behavioral and chemosensory assays, we found that fly-microbe attractions are shaped by the identity of the host microbiota. Conventional flies exhibit preference for their associated Lactobacillus, a behavior also present in axenic flies as adults and marginally as larvae. By contrast, fly preference for Acetobacter is primed by early-life exposure and can override the innate preference. These microbial preferences are largely olfactory guided and have profound impact on host foraging, as flies continuously trade off between acquiring beneficial microbes and balancing nutrients from food. Our study shows a role of animal microbiota in shaping host fitness-related behavior through their chemosensory responses, opening a research theme on the interrelationships between the microbiota, host sensory perception, and behavior.

Breeding habitat preference of preimaginal black flies (Diptera: Simuliidae) in Peninsular Malaysia

To investigate the breeding habitat preference of black flies, a comprehensive black fly survey was conducted for the first time in Peninsular Malaysia. Preimaginal black flies (pupae and larvae) were collected manually from 180 stream points encompassing northern, southern, central and east coast of the Peninsular Malaysia. A total of 47 black fly species were recorded in this study. The predominant species were Simulium trangense (36.7%) and Simulium angulistylum (33.3%). Relatively common species were Simulium cheongi (29.4%), Simulium tani (25.6%), Simulium nobile (16.2%), Simulium sheilae (14.5%) and Simulium bishopi (10.6%). Principal Component Analysis (PCA) of all stream variables revealed four PCs that accounted for 69.3% of the total intersite variance. Regression analysis revealed that high species richness is associated with larger, deeper, faster and higher discharge streams with larger streambed particles, more riparian vegetation and low pH (F=22.7, d.f.=1, 173; P<0.001). Relationship between species occurrence of seven common species (present in >10% of the sampling sites) was assessed. Forward logistic regression analysis indicated that four species were significantly related to the stream variables. S. nobile and S. tani prefer large, fast flowing streams with higher pH, large streambed particles and riparian trees. S. bishopi was commonly found at high elevation with cooler stream, low conductivity, higher conductivity and more riparian trees. In contrast, S. sheilae was negatively correlated with PC-2, thus, this species commonly found at low elevation, warmer stream with low conductivity and less riparian trees. The results of this study are consistent with previous studies from other geographic regions, which indicated that both physical and chemical stream conditions are the key factors for black fly ecology.

Cold-seeking behaviour mitigates reproductive losses from fungal infection in Drosophila.

Summary Animals must tailor their life‐history strategies to suit the prevailing conditions and respond to hazards in the environment. Animals with lethal infections are faced with a difficult choice: to allocate more resources to reproduction and suffer higher mortality or to reduce reproduction with the expectation of enhanced immunity and late‐age reproduction. However, the strategies employed to mediate shifts in life‐history traits are largely unknown.Here, we investigate the temperature preference of the fruit fly, Drosophila melanogaster, during infection with the fungal pathogen, Metarhizium robertsii, and the consequence of temperature preference on life‐history traits.We have measured the temperature preference of fruit flies under different pathogen conditions. We conducted multiple fitness assays of the host and the pathogen under different thermal conditions. From these data, we estimated standard measures of fitness and used age‐specific methodologies to test for the fitness trade‐offs that are thought to underlie differences in life‐history strategy.We found that fungus‐infected fruit flies seek out cooler temperatures, which facilitates an adaptive shift in their life‐history strategy. The colder temperatures preferred by infected animals were detrimental to the pathogen because it increased resistance to infection. But, it did not provide net benefits that were specific to infected animals, as cooler temperatures increased lifetime reproductive success and survival whether or not the animals were infected. Instead, we find that cold‐seeking benefits infected animals by increasing their late‐age reproductive output, at a cost to their early‐age reproductive output. In contrast, naive control flies prefer warmer temperatures that optimize early‐age reproductive, at a cost to reproductive output at late ages.These findings show that infected animals exhibit fundamentally different reproductive strategies than their healthy counterparts. Temperature preference can facilitate shifts in strategy, but not without inevitable trade‐offs.

Preferencia de mosca blanca (Paraleyrodes sp.) por cultivares de aguacate (Persea americana Mill.) en Fresno, Tolima

La mosca blanca es una importante plaga que afecta el aguacate, y en Colombia no se posee suficiente información sobre este insecto. En este estudio se evaluó la incidencia de mosca blanca Paraleyrodes sp. pos. bondari en cuatro cultivares de aguacate (Choquette, Hass, Lorena, Santana). Se caracterizó el manejo del cultivo realizado por los agricultores y se analizó su efecto sobre la presencia del insecto en tres cultivares (Choquette, Hass, Lorena). Se encontraron algunos metabolitos secundarios en hojas de los cultivares Hass y Lorena y se evaluó el efecto del extracto de sus hojas sobre la mortalidad y el índice de repelencia de adultos de mosca blanca. Se presentó interacción entre el manejo del cultivo y los cultivares para la presencia del insecto; el manejo moderadamente químico tuvo la menor infestación en todos los cultivares. El incremento de fertilización edáfica y de insecticidas químicos incrementó la población del insecto, y la remoción de una hemiparásita la disminuyó. El cultivar Lorena presentó la mayor preferencia de mosca, aumento de población del insecto cuando hubo interacción entre cultivar y hojas maduras, índice de repelencia neutral, y mayor porcentaje de carbohidratos totales y no reductores. El cultivar Hass presentó mayor cantidad de cumarinas, terpenos y esteroides, y alto índice de repelencia. La atracción de Lorena por el insecto se debe a la presencia de carbohidratos, y la repelencia de Hass, a la de terpenos y/o esteroides. Se debe dirigir el trabajo de investigación sobre mosca blanca en aguacate hacia el cultivar Lorena.