Arthur W. Ewing

Pulse interval as a critical parameter in the courtship song of Drosophila melanogaster

Summary o 1. Males of Drosophila melanogaster produce courtship songs which sexually stimulate the females. The songs consist of trains of single cycle pulses of sound of 3 msec length separated by intervals of 34 msec. 2. The effect on female receptivity of varying pulse length and pulse interval was tested by using simulated songs. 3. The species specific nature of the song is determined by pulse interval and not pulse length.

THE COURTSHIP SONGS OF DROSOPHILA

1. The males of many Drosophila species perform wing displays during courtship and there is evidence that the stimuli provided by these is primarily acoustic. 2. The songs produced by members of the melanogaster and obscura species groups were recorded and analysed. 3. The songs consisted of regularly repeated pulses of sound. The frequency within the pulses and the interval between them varied between species but was constant and characteristic for each species. 4. It is suggested that the songs are codes which allow females to recognise con-specific mates.

Male size and mating success in Drosophila melanogaster: the roles of male and female behaviour.

Abstract Larger D. melanogaster males delivered more courtship to virgin females, produced more courtship song and sang more loudly than smaller males. They also moved around more when not courting. All courtships were terminated by the female decamping or while she was moving. Females decamped equally often when courted by large and small males but were more likely to be moving while courted by large males, and this appeared to be a consequence of the faster running and courtship tracking speeds of larger males. The results suggest that scramble competition between males to deliver courtship is important in determining mating success, but not that females discriminate between males of different sizes. However, the higher audibility of louder sounds to females and their tendency to move while courted both have the effect of favouring larger males.

FUNCTIONAL ASPECTS OF DROSOPHILA COURTSHIP

1. The elements that make up the courtship behaviour of males and of females are briefly described. It is pointed out that some of the terms used, such as female ‘repelling’ behaviour, are misleading as they do not reflect the known functions of the behaviours.

The influence of wing area on the courtship behaviour of Drosophila melanogaster

1. 1. In the male of Drosophila melanogaster the component of courtship behaviour which plays the major role in sexually stimulating the female is wing vibration. 2. 2. Wing area was changed by three methods: (a) By lowering the temperature during preimaginal development, (b) By selective breeding, (c) By amputation. 3. 3. The sexual success of males with different wing areas was measured and it was found that males with large wings were more successful in obtaining mates than those with small or partially amputated wings. 4. 4. The relationship between wing area and sexual success appeared to be linear thus demonstrating the additive nature of the stimulation provided via vibration. 5. 5. An extrapolation from these results suggested that approximately 80 per cent, of the sexual stimulation is normally provided by wing vibration. 6. 6. The relevance of these results to some previously published work is discussed.

The genetic basis of sound production in Drosophila pseudoobscura and D. persimilis

Abstract 1. 1. Males of the sibling species Drosophila pseudoobscura and D. persimilis perform courtship songs which differ both quantitatively and qualitatively. Pseudoobscura produces two songs, a low repetition rate song which consists of trains of 525 Hz pulses at 6 per sec and a high repetition rate one in which 250 Hz pulses are repeated at 24 times per sec. In persimilis the low repetition rate song is absent or occurs in a very abbreviated form and the high repetition rate song consists of 525 Hz pulses repeated at 15 times per sec. 2. 2. The inheritance of these songs was investigated by examining the songs produced by the F1 and backcross progeny of crosses between the species. 3. 3. The presence of the low repetition rate song and the frequency within pulse of the high repetition rate songs are controlled by genes located on the X chromosome. The pulse repetition rate of the high repetition rate song is inherited independently from the former characters. 4. 4. Possible evolutionary implications of the mode of inheritance of the songs are discussed.

Attempts to select for spontaneous activity in Drosophila melanogaster

Summary 1. This paper describes two attempts to select for high and low levels of spontaneous activity in Deosophila melanogaster . 2. In the first experiment the selection procedure necessitated using 25 flies at a time in the selection apparatus. The results were that the levels of reactivity between flies were changed and not spontaneous activity. 3. These changes were found to have effects on the courtship behaviour of the flies. The mutual interference between flies from the lines showing a high degree of reactivity decreased the efficiency of courtship. This was shown to be due to both males and females. Reduced interference between flies from the lines showing lowered reactivity resulted in courtship behaviour that contained more of the high threshold courtship elements. 4. In the second experiment selection was based on the activity of individual flies. A response for lowered activity was obtained in the selection apparatus but not for increased activity. 5. An analysis of this change showed that once again selection had failed to change the level of spontaneous activity. Selection was based on the speed with which flies passed through a series of chambers connected by narrow funnels. In this case selection had resulted in lines of flies which were unwilling to enter confined spaces, such as the funnels. 6. This “claustrophobic” effect was shown to be due to the flies reacting to visual stimuli from the sides of the funnels.

The antenna of Drosophila as a ‘love song’ receptor

ABSTRACT. Behavioural experiments have demonstrated that the songs of Drosophila species are involved in courtship and aggression, and suggest that the songs are perceived via Johnstons organ. Direct electrophysiological evidence is here presented to show that the antenna of Drosphila is indeed capable of responding to the range of sounds produced by the flies.

Sexual selection, sexual isolation and the evolution of song in the Drosophila repleta group of species

The evolution of male courtship song pattern in fruit flies of the repleta group within the genus Drosophila is described. We suggest that the archetypal song was composed of two distinct components, an ‘A’ song with short, regular pulse trains which occurred at the beginning of courtship, and a ‘B’ song consisting of longer pulse trains of more widely spaced pulses occurring later in courtship. During evolution of the repleta group some species have lost the A song, others the B song and, in many species, the latter has become less regular and more complex in form. A songs appear to be involved primarily in species recognition and have been subject to stabilizing selection while the B songs sexually stimulate females and have therefore evolved rapidly through the action of sexual selection. Other factors influencing the evolution of song patterns have been certain physiological and energetic constraints.

The neuromuscular basis of courtship song inDrosophila: The role of the direct and axillary wing muscles

Summary1.Power for both flight and for courtship song inDrosophila is provided by the indirect, myogenic, flight muscles (Fig. 7). The axillary and direct wing muscles (Fig. 1) control wing extension, most of the parameters of wing movement and the timing of song pulses. The role of these muscles during song was investigated electrophysiologically.2.Most of the axillary muscles fire during pulse song inter pulse intervals (Figs. 4, 5). It is suggested that the role of some of these muscles is to depress the wing or otherwise distort the thorax so as to stretch the dorsal ventral muscles thus initiating their contraction to produce the sound producing up-stroke of the wing.3.The basalar muscles fire synchronously with wing movements on the up-stroke of flight, sine song and pulse song (Fig. 2). The mode of action of these muscles is not clear but they are probably concerned with maintaining tension of the thoracic box and thus affect the amplitude of wing movement. They may also effect wing extension.4.The sternobasalar muscle also fires on the upstroke but only during pulse song and not sine song (Fig. 3). It is suggested that contraction of the sternobasalar muscle dampens the wing oscillation so that only single cycle pulses of sound are produced.5.Lesions of the sternobasalar muscle are accompanied by the production of polycyclic sound pulses and this supports the above hypothesis (Fig. 6).