Wing Spreading Research Articles

Ancestral neural circuits potentiate the origin of a female sexual behavior in Drosophila

Courtship interactions are remarkably diverse in form and complexity among species. How neural circuits evolve to encode new behaviors that are functionally integrated into these dynamic social interactions is unknown. Here we report a recently originated female sexual behavior in the island endemic Drosophila species D. santomea, where females signal receptivity to male courtship songs by spreading their wings, which in turn promotes prolonged songs in courting males. Copulation success depends on this female signal and correlates with males’ ability to adjust his singing in such a social feedback loop. Functional comparison of sexual circuitry across species suggests that a pair of descending neurons, which integrates male song stimuli and female internal state to control a conserved female abdominal behavior, drives wing spreading in D. santomea. This co-option occurred through the refinement of a pre-existing, plastic circuit that can be optogenetically activated in an outgroup species. Combined, our results show that the ancestral potential of a socially-tuned key circuit node to engage the wing motor circuit facilitates the expression of a new female behavior in appropriate sensory and motivational contexts. More broadly, our work provides insights into the evolution of social behaviors, particularly female behaviors, and the underlying neural mechanisms.

Platform development and gliding optimization of a robotic flying fish with morphing pectoral fins

The aquatic-aerial robot with the free interface crossing can enhance adaptability in complex aquatic environments. However, its design is extremely challenging for the striking discrepancies in propulsion principles. The flying fish in nature exhibits remarkable multi-modal cross-domain locomotion capability, such as high-maneuvers swimming, agile water-air crossing, and long-distance gliding, providing extensive inspiration. In this paper, we present a unique aquatic-aerial robotic flying fish with powerful propulsion and a pair of morphing wing-like pectoral fins to realize cross-domain motion. Furthermore, to explore the gliding mechanism of flying fish, a dynamic model with a morphing structure of pectoral fins is established, and a double deep Q-network-based control strategy is proposed to optimize the gliding distance. Finally, experiments were conducted to analyze the locomotion of the robotic flying fish. The results suggest that the robotic flying fish can successfully perform the ‘fish leaping and wing spreading’ cross-domain locomotion with an exiting speed of 1.55 m s−1 (5.9 body lengths per second, BL/s) and a crossing time of 0.233 s indicating its great potential in cross-domain. Simulation results have validated the effectiveness of the proposed control strategy and indicated that the dynamical adjustment of morphing pectoral fins contributes to improving the gliding distance. The maximum gliding distance has increased by 7.2%. This study will offer some significant insights into the system design and performance optimization of aquatic-aerial robots.

Thermoregulation and heat exchange in ospreys (Pandion haliaetus).

The osprey (Pandion haliaetus) is a cosmopolitan and long-distant migrant, found at all thermal extremes ranging from polar to tropical climates. Since ospreys may have an unusually flexible thermal physiology due to their migration over, and use of, a wide range of habitats, they represent an interesting study system to explore thermoregulatory adaptations in a raptor. In this study, we investigated the efficiency of heat exchange between body and environment in ospreys using micro-computed tomography (μ-CT), infrared thermography and behavioral observations. μ-CT revealed that the osprey bill has its largest potential for heat exchange at the proximal bill region, where arteries are situated most closely under the surface. However, thermal images of 10 juvenile ospreys showed that the bill contributes to only 0.3% of the bird's total heat exchange. The long legs and protruding claws played a more prominent role as heat dissipation areas with a contribution of 6% and 7%, respectively. Operative thresholds, i.e. the ambient temperature below which heat is lost, were high (>38.5°C) in these body parts. However, we found no indication of active regulation of heat exchange. Instead we observed multiple behavioral adaptations starting at relatively low ambient temperatures. At 26.3°C ospreys had a 50% probability of showing panting behavior and above 27.9°C they additionally spread their wings to enable heat dissipation from the less insulated ventral side. The thermal images revealed that at an ambient temperature of 32.1°C ospreys had a 50% probability of developing a ≥2°C and up to 7.5°C colder stripe on the head, which was likely caused by cutaneous evaporation. Our observations suggest that ospreys more strongly rely on behavioral mechanisms than on active thermal windows to cope with heat stress. This study not only improves our understanding of the role of different body parts in ospreys' total heat exchange with the environment but further provides an insight about additional adaptations of this raptor to cope with heat stress.

Completion of metamorphosis after adult emergence in Ceratitis capitata (Diptera: Tephritidae).

The ecdysis of the imago is a crucial step in the development of holometabolous insects. However, no information on several aspects of Ceratitis capitata imago emergence and subsequent body maturation is available. We analysed behavioural events and evaluated the oxygen consumption and the dynamics of carbohydrate and lipid reserves during puparium extrication and in newly emerged imago until full wing expansion. A system for recording images with the corresponding software for image analysis was built for this purpose. After extrication, C. capitata showed two early postemergence phases: walking (6.56 ± 4.01 min, 6.2% of the wing spreading period, WSP) and the phase without locomotor motion (98.75 ± 26.04 min; 93.8% WSP). Three main events were recognized during the last phase. The first involved an initial expansion of the wings (11.12 ± 4.32 min). The second event was the progressive tanning of the body cuticle in general and the wing veins in particular, and the last entailed the definitive expansion of the wings to attain the characteristic arrow-shaped wing aspect. Our studies here complement previous descriptions of the tanning process of newly emerged medfly adults (Pérez etal., 2018). As a consequence of the results presented here, we consider that the initial events of the newly emerged adult could be interpreted as the last steps of metamorphosis.

Behavioural Patterns and Postnatal Development in Pups of the Asian Parti-Coloured Bat, Vespertilio sinensis.

Simple SummaryDuring the development of animals from juvenile to adult, their behaviour, morphology, and physiology can be altered to accommodate specific developmental periods. Early development in young animals directly affects the acquisition and maturation of behavioural skills and neurological functions in adults. Studying the behavioural development of young animals can help reveal the formation and evolution of animal behaviour. As the only mammalian group that flies, studying the behavioural development of young bats can help improve our understanding of bat flight behaviour. From our observations in the laboratory, we found that wing flapping and wing spreading behaviours in young bats promote earlier flight attempts.Behavioural development is an important aspect of research on animal behaviour. In bats, many studies have been conducted on the development of flight behaviour, but the postnatal behavioural development of bats remains largely unexplored. We studied the behaviours and postnatal development of infant bats by conducting controlled video recorded experiments. Our results showed that before weaning, Asian parti-coloured bats (Vespertilio sinensis) were able to exhibit four types of behaviours, namely, crawling, head moving, wing flapping, and wing spreading, and these behaviours are different from those observed in experiments with adult bats. The number of occurrences of these behaviours was correlated with age and scaled mass index. Furthermore, the number of occurrences of these behaviours in young bats could also reflect their physical developmental status. In young bats, wing flapping and spreading might be a type of play behaviour. These behaviours were negatively correlated with the time of the first flight, indicating that they might help to promote individual physical development. Our results provide fundamental data for revealing the ontogenetic and neurophysiological mechanisms of behavioural development in bats.

Extracellular activity of NBAD-synthase is responsible for colouration of brown spots in Ceratitis capitata wings

After the emergence of the Ceratitis capitata imago, the pale and folded wings are expanded and sclerotized to acquire the definitive form and to stabilize the cuticle. The wings of this fly show a specific pattern of brownish and black spots. Black spots are pigmented by melanin, whereas there was scarce information about the development of the brownish spots. N-beta-alanydopamine (NBAD) is the main tanning precursor in C. capitata body cuticle, and we hypothesized that it may be responsible for the colouration of the brownish spots. We determined the topology and timing of NBAD synthesis and deposition to attain the species-specific colouration pattern. We demonstrated that during the first hours the colour of the brownish spots was principally determined by the tanning of the hairs. Haemolymph circulation through the veins is required to tan the wings. We confirmed that soon after wing spreading, most of the wing epidermal cells disappeared. Thus, the tanning of the brown spots was accomplished when the wing lamina was devoid of cells. NBAD synthase (NBAD-S; Ebony protein in D. melanogaster) activity in wings was detected in pharate adults and lasted several days after the emergence, even after the end of the tanning process. This observation is in contrast to epidermal NBAD-S activity in the body, where it was nearly undetectable 48 h post emergence. Our results indicate that NBAD-S was exported and deposited into the extracellular matrix of the brown spot areas before cell death and that tanning occurs through gradual export of NBAD precursors (dopamine and b-alanine) from veins.

Effect of dietary synbiotic supplement on behavioral patterns and growth performance of broiler chickens reared under heat stress

This study examined the effects of a dietary synbiotic supplement on the behavioral patterns and growth performance of broiler chickens exposed to heat stress (HS). Three hundred sixty 1-day-old male Ross 708 broiler chicks were distributed among 24 floor pens (15 chicks per pen); each pen was randomly assigned to one of 3 dietary treatments containing a synbiotic at 0 (control), 0.5 (0.5X) and 1.0 (1.0X) g/kg. From d 15 to 42, birds were exposed to HS at 32°C daily from 08:00 to 17:00. Five broiler chickens were randomly marked in each pen for behavioral observation. Instantaneous scan sampling was used to record the birds' behavioral patterns. Performance parameters were measured on d 7, 14, 28 and 42. The synbiotic fed birds exhibited more standing, sitting, walking, feeding, preening and less wing spreading and panting behaviors (P < 0.05) compared to birds fed the control diet. The synbiotic group also had higher BW, BW gain and feed intake on d 7, 14 and 42 (P < 0.05), and higher BW, feed intake and feed conversion ratio at d 28 (P < 0.01). There were no treatment effects on drinking behavior, BW gain on d 28 and feed conversion ratio on d 42 (P > 0.05). There were few dose-related differences of the synbiotic on production performance; namely, the 1.0X concentration resulted in the highest BW and feed intake on d 14 and 42 (P < 0.05), while BW gain was higher compared to the control group only on d 42 (P < 0.05). The results suggest that the synbiotic supplement may prove to be an important management tool for the broiler industry to diminish the negative effects of HS, potentially safeguarding the welfare and production of broiler chickens, particularly in areas that experience hot climates.

Supplementation of Bacillus subtilis-based probiotic reduces heat stress-related behaviors and inflammatory response in broiler chickens.

Probiotics reduce stress-related inflammation and abnormal behaviors in humans and rodents via regulation of the microbiota-gut-brain axis. The objective of this study was to determine if probiotic, Bacillus subtilis, has similar functions in broiler chickens under heat stress (HS). Two hundred forty 1-d-old broiler chicks were assigned to 48 pens with 4 treatments: Thermoneutral (TN)-RD (regular diet), TN-PD (the regular diet mixed with 1 × 106 CFU/g feed probiotic), HS-RD and HS-PD. Probiotic (Sporulin) was fed from day 1; and HS at 32°C for 10 h daily was initiated at day 15. The data showed that final BW, average daily gain , and feed conversion efficiency were improved in PD groups as compared to RD groups regardless of the ambient temperature (P < 0.01). Heterophil to lymphocyte ratio was affected by treatment and its value was in the order of HS-RD > HS-PD > TN-RD > TN-PD birds (P < 0.01). Compared to TN birds, HS birds spent more time in wing spreading, panting, squatting close to the ground, drinking, sleeping, dozing, and sitting but spent less time in eating, standing, and walking (P < 0.05 or 0.01). In addition, HS birds had greater levels of hepatic IL-6, IL-10, heat shock protein (HSP)70, and HSP70 mRNA expression (P < 0.01) and greater levels of cecal IgA and IgY (P < 0.01) compared to TN birds. Within TN groups, TN-PD birds had greater concentrations of hepatic IL-10 (P < 0.05) and cecal IgA (P < 0.01) than TN-RD birds. Within HS groups, HS-PD birds spent less time in wing spreading, panting, squatting close to the ground, drinking, sleeping, dozing, and sitting but spent more time in eating, foraging, standing, and walking than HS-RD birds (P < 0.05 or 0.01). The HS-PD birds also had lower concentrations of hepatic IL-6 and HSP70 (P < 0.01), whereas greater levels of IL-10 (P < 0.05) and lower concentrations of cecal IgA and IgY (P < 0.01). These results indicate that broilers fed the probiotic, B. subtilis, are able to cope with HS more effectively by ameliorating heat-induced behavioral and inflammatory reactions through regulation of microbiota-modulated immunity.

Nighttime behavioral study of flying foxes on the southern coast of West Java, Indonesia.

Flying foxes are important in the maintenance of forests and diversity. However, knowledge of their behavioral ecology, especially of movement and foraging patterns, which are essential for conservation and management of their populations, are not well known. Therefore, movement behavior of two individuals of Pteropus vampyrus were examined using an Argos telemetry system, and foraging pattern of Pteropus spp. was directly observed, at West Java province, Indonesia in October 2017. The maximum distance between the location at which bats were released and their furthest roost, recorded via satellite telemetry, was approximately 100 km. This reflects the long-distance flight ability of P. vampyrus. Daytime roosting sites and nighttime foraging places consisted of several types of habitats, such as intact forests, agricultural lands, and residential areas. This evidence indicated that there was habitat overlap between humans and bats in West Java province. According to direct observation of the behaviors of flying foxes at two locations within residential areas, various activities such as wing spreading, excretion, fighting, aggressive calls, movement, hanging relax, and hanging alert were found. The number of bat-visits to the trees varied among night hours, and had a positive correlation with the number of fruit dropping. The data obtained in this study have improved our understanding of nighttime behavior and habitat utilization of P. vampyrus, that can be used to support landscape management, species conservation, and disease prevention in regions of Southeast Asia.

Population Status and Diurnal Behaviour of the Indian Flying Fox Pteropus giganteus (Brünnich, 1782) in Kathmandu Valley, Nepal

This study documents the population status and behaviour of the Indian Flying Fox (Pteropus giganteus) at two locations in the temperate environment of the Kathmandu Valley, Nepal. During the five-month study, from 14th July, 2014 to 2nd January, 2015, peak populations were observed in October, 2014 at Sallaghari (1550 individuals) and Keshar Mahal (949 individuals). The behavioural study resulted in 1130 observed events of 10 different behavioural activities at Sallaghari and 1158 events of the same activities at Keshar Mahal. Sleeping, grooming, wing spreading and wing flapping were frequently observed at both study sites. The behaviour of P. giganteus is influenced by the weather and air temperature irrespective of hours of the day and date of observation. Habitat destruction, lack of food, pollution and misconception were the major threats to P. giganteus perceived by local people in course of interviews. Knowledge regarding the population size and behaviours of wildlife species is essential to understand the conservation needs for the survival and management of wild animals and their habitat. This study provides baseline information for two populations of Indian flying fox (P. giganteus) in Kathmandu Valley Nepal.

Cooled perch effects on performance and well-being traits in caged White Leghorn hens

We assessed the effects of chilled water cooling perches on hen performance and physiological and behavioral parameters under “natural” high temperatures during the 2013 summer with a 4-hour acute heating episode. White Leghorns at 16 wk of age (N = 162) were randomly assigned to 18 cages (n = 9) arranged into 3 units. Each unit was assigned to one of the 3 treatments through 32 wk of age: 1) cooled perches, 2) air perches, and 3) no perches. Chilled water (10°C) was circulated through the cooled perches when cage ambient temperature exceeded 25°C. At the age of 27.6 wk, hens were subjected to a 4-hour acute heating episode of 33.3°C and plasma corticosterone was determined within 2 hours. Egg production was recorded daily. Feed intake and egg and shell quality were measured at 5-week intervals. Feather condition, foot health, adrenal and liver weights, plasma corticosterone, and heat shock protein 70 mRNA were determined at the end of the study at 32 wk of age. The proportion of hens per cage perching, feeding, drinking, panting, and wing spreading was evaluated over one d every 5 wks and on the d of acute heat stress. There were no treatment effects on the measured physiological and production traits except for nail length. Nails were shorter for cooled perch hens than control (P = 0.002) but not air perch hens. Panting and wing spread were observed only on the day of acute heat stress. The onset of both behaviors was delayed for cooled perch hens, and they perched more than air perch hens following acute heat stress (P = 0.001) and at the age 21.4 wk (P = 0.023). Cooled perch hens drank less than control (P = 0.019) but not air perch hens at the age 21.4 wk. These results indicate that thermally cooled perches reduced thermoregulatory behaviors during acute heat stress, but did not affect their performance and physiological parameters under the ambient temperature imposed during this study.

The ability of White Leghorn hens with trimmed comb and wattles to thermoregulate

It is estimated that each year over 19 million pullets in the United States have their combs partially trimmed at a young age to improve egg production and feed efficiency. A possible disadvantage of trimming is that the comb and wattles may be essential for thermoregulation during hot weather allowing for conductive cooling of the blood through vasodilation of superficial vessels in these integumentary tissues. The objective of this study was to investigate the effects of partial comb and wattle removal, performed at 21 d of age, on the ability of White Leghorns to thermoregulate before, during, and after an imposed heating episode that averaged 34.6°C for 50.5h. An increase in mortality at 20h and body temperature at 48h post initiation of the heating episode demonstrated that hens with trimmed comb and wattles were not able to cope with heat stress as effectively as controls. The increase in wattle temperature in controls as compared to trimmed hens during the heating episode and following heat stress provides supportive evidence that blood pools to the peripheral surface for conductive heat loss. During high temperatures typical of summer, trimmed hens attempted to compensate for their lack of ability to transfer heat from their comb and wattles to the environment through increased proportion of panting and wing spreading. Under less extreme conditions with lowered ambient temperatures, the trimming of the comb and wattles did not impair the ability of hens to thermoregulate, as body temperatures and behavior were similar to controls with no mortality. Egg weight was the only production parameter adversely affected by the trimming of the comb and wattles as compared to controls. The implication is that hens need their combs and wattles to thermoregulate effectively during periods of high environmental temperature. Pullets should not be subjected to a comb and wattle trim if they are housed in laying facilities that are not appropriately cooled during the summer.

Light and peptidergic eclosion hormone neurons stimulate a rapid eclosion response that masks circadian emergence in Drosophila.

Light signals can entrain circadian clocks, but they can also mask aspects of the circadian output. We have analyzed the masking effects of a lights-on (LOn) signal on Drosophila eclosion. The LOn response results in 12-21% of the flies that emerge on a given day eclosing within 10 min of the LOn signal. Flies that lack the neuropeptide eclosion hormone (EH), or in which its release is inhibited by the tetanus toxin light chain, lack the response. Optic photoreceptors in both the ocelli and the compound eyes appear to be required for the response. The LOn signal has two effects: (1) it drastically reduces the interval between EH release and eclosion, presumably by suppressing a transient descending inhibition that immediately follows EH release, and (2) it stimulates premature EH release. The LOn signal does not influence the latency of wing spreading, an EH-regulated post-ecdysis behavior.

Why is wing-spreading behaviour absent in blue-eyed shags?

Centre d’Etudes Biologiques de Chize´, Beauvoir-sur-Niort(Received 24 June 2006; initial acceptance 10 August 2006;final acceptance 24 November 2006; published online 15 August 2007; MS. number: SC-1297R)Wing spreading is a general behaviour in cormorants, andhas been described worldwide in most species (Orta 1992).Yet, this behaviour is missing (with some exceptions, seebelow) in the species belonging to the so-called ‘blue-eyed shag complex’ (Bernstein & Maxson 1981), hereafterreferred to as ‘the complex’, a group of cormorants livingon the coasts and islands of the waters of the SouthernOcean between roughly 40 S and 70 S latitude (Patagonia,Antarctic Peninsula, subAntarctic Islands, New Zealand)and comprising 13 species that have close morphologicalsimilarities (Siegel-Causey 1988).The following observation is an example of what is veryrarely seen in blue-eyed shags. A wing-spreading behav-iour was observed in an adult Kerguelen shag, Phalacro-corax verrucosus, on 29 December 2005. This behaviourwas noticed on the coast of Stoll Island (49 26

Evolutionary conservation of bursicon in the animal kingdom

Bursicon bioactivity is essential for tanning of the exoskeleton and for wing spreading behavior that occur in newly emerged adult insects. Previously, we demonstrated that in the fruit fly, Drosophila melanogaster, bursicon exists as a heterodimeric cystine knot protein that activates the leucine-rich repeats containing G protein-coupled receptor 2 (DLGR2). By performing similarity based in silico searches in genomic and complementary DNA databases, we identified bursicon homologous sequences in several protostomian as well as deuterostomian invertebrates. In the genome of the honeybee, Apis mellifera, the coding regions for bursicon cystine knot subunits are organized in a genomic locus of approximately 4 kilobase pairs. Reverse transcription PCR analysis indicates that this region likely codes for two distinct bursicon cystine knot subunits. Our results illustrate the remarkable conservation of bursicon in invertebrate species and provide an avenue for functional analyses of this hormone in a wide range of animal species.

Daytime behaviour of the grey-headed flying fox Pteropus poliocephalus Temminck (Pteropodidae: Megachiroptera) at an autumn/winter roost.

The grey-headed flying fox (Pteropus poliocephalus Temminck) is a threatened large fruit bat endemic to Australia. It roosts in large colonies in rainforest patches, mangroves, open forest, riparian woodland and, as native habitat is reduced, increasingly in vegetation within urban environments. The general biology, ecology and behaviour of this bat remain largely unknown, which makes it difficult to effectively monitor, protect and manage this species. The current study provides baseline information on the daytime behaviour of P. poliocephalus in an autumn/winter roost in urban Sydney, Australia, between April and August 2003. The most common daytime behaviours expressed by the flying foxes were sleeping (most common), grooming, mating/courtship, and wing spreading (least common). Behaviours differed significantly between times of day and seasons (autumn and winter). Active behaviours (i.e., grooming, mating/courtship, wing spreading) occurred mainly in the morning, while sleeping predominated in the afternoon. Mating/courtship and wing spreading were significantly higher in April (reproductive period) than in winter (non-reproductive period). Grooming was the only behaviour that showed no significant variation between sample periods. These results provide important baseline data for future comparative studies on the behaviours of flying foxes from urban and ?natural? camps, and the development of management strategies for this species.

Identification of the Gene Encoding Bursicon, an Insect Neuropeptide Responsible for Cuticle Sclerotization and Wing Spreading

To accommodate growth, insects must periodically replace their exoskeletons. After shedding the old cuticle, the new soft cuticle must sclerotize. Sclerotization has long been known to be controlled by the neuropeptide hormone bursicon [1, 2], but its large size of 30 kDa has frustrated attempts to determine its sequence and structure. Using partial sequences obtained from purified cockroach bursicon [3], we identified the Drosophila melanogaster gene CG13419 as a candidate bursicon gene. CG13419 encodes a peptide with a predicted final molecular weight of 15 kDa, which likely functions as a dimer. This predicted bursicon protein belongs to the cystine knot family, which includes vertebrate transforming growth factor-β (TGF-β) and glycoprotein hormones [4]. Point mutations in the bursicon gene cause defects in cuticle sclerotization and wing expansion behavior. Bioassays show that these mutants have decreased bursicon bioactivity. In situ hybridization and immunocytochemistry revealed that bursicon is co-expressed with crustacean cardioactive peptide (CCAP). Transgenic flies that lack CCAP neurons [5] also lacked bursicon bioactivity. Our results indicate that CG13419 encodes bursicon, the last of the classic set of insect developmental hormones. It is the first member of the cystine knot family to have a defined function in invertebrates. Mutants show that the spectrum of bursicon actions is broader than formerly demonstrated.

Activation of the cAMP/PKA signaling pathway is required for post-ecdysial cell death in wing epidermal cells ofDrosophila melanogaster

At the last step of metamorphosis in Drosophila, the wing epidermal cells are removed by programmed cell death during the wing spreading behavior after eclosion. The cell death was accompanied by DNA fragmentation demonstrated by the TUNEL assay. Transmission electron microscopy revealed that this cell death exhibited extensive vacuoles, indicative of autophagy. Ectopic expression of an anti-apoptotic gene, p35, inhibited the cell death, indicating the involvement of caspases. Neck ligation and hemolymph injection experiments demonstrated that the cell death is triggered by a hormonal factor secreted just after eclosion. The timing of the hormonal release implies that the hormone to trigger the death might be the insect tanning hormone, bursicon. This was supported by evidence that wing cell death was inhibited by a mutation of rickets, which encodes a G-protein coupled receptor in the glycoprotein hormone family that is a putative bursicon receptor. Furthermore, stimulation of components downstream of bursicon, such as a membrane permeant analog of cAMP, or ectopic expression of constitutively active forms of G proteins or PKA, induced precocious death. Conversely, cell death was inhibited in wing clones lacking G protein or PKA function. Thus, activation of the cAMP/PKA signaling pathway is required for transduction of the hormonal signal that induces wing epidermal cell death after eclosion.

Female preference for fly song: playback experiments confirm the targets of sexual selection

The courtship song ofDrosophilais thought to be involved in sexual selection and species recognition. Because of the mating system of flies, however, directly demonstrating that song influences female preference is difficult. The majority of previous studies have used an experimental design that potentially confounds male and female reactions to song. InD.montana, correlational evidence has suggested that males that produce short sound pulses consisting of a high number of sound cycles (i.e. a high carrier frequency) have a higher mating success than other males. In this study, we played synthetic song that varied in pulse length and carrier frequency to individual females in the laboratory, both alone and in the presence of mute males. We scored female preference via an acceptance posture, ‘wing spreading’, which the females of this species usually display prior to mounting by a male. Females responded to synthetic song in the absence of males. The presence of mute males significantly increased their overall responsiveness, but the relative effectiveness of the songs did not change, eliminating male reaction to song as a possible confounding factor in the results. The interaction between pulse length and carrier frequency determined the discrimination between song types, with females responding most readily to song consisting of short pulses with a high carrier frequency. Thus, direct examination of female preferences supports the previous studies of male mating success, and confirms female song preference as a likely determinant of male mating success.

Female wing spreading as acceptance signal in theDrosophila virilis group of species

Females of manyDrosophila species spread apart their wings prior to copulation. In the present study we found female wing spreading to provoke male copulation attempts inDrosophila virilis-group species, helping the males to attempt copulation when the female is ready to mate. The males of most species, however, rarely responded to female wing spreading by copulation attempt without licking the female genitalia before and/or after female wing spreading bout. Blocking the female genitalia (D. virilis, D. novamexicana) reduces males' tendency to attempt copulation after female wing spreading. In these, and most other species of the group, female wing spreading seems to be an efficient signal only when combined with stimuli from female genitalia.