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On the coloration of fast-moving signalling stimili in the nature

By virtue of an evolutionarily determined feature of color vision, insects, fish and other animals see fast-moving objects as colorless (Gehres & Neumeyer, 2007; Stojcev et al., 2011). In animals, the fastest moving parts are wings (in insects and birds: e.g., see Schön, 2009). So styding natural coloration of wings allows to understand deeper the phenomenon of color blindness in respect of fast-moving objects.

In insects,  strong correlation between the presense of eye-catching, signalling marks in wing coloration and the frequency of wing-beats is observed.

In particular, wasps, horneybees and other stinging insects have among all insects ones of the fastest beating wings, which are transparent or semi-transparent and have no eye-catching marks. The frequency of wing-beats, F, in the stinging insects is ranged approximately within 100-250 beats per second. For example, for common wasp, Vespa vulgaris, F = 140 b/s, for European honeybee, Apis mellifera, F = 240-250 b/s (Byrne, 1988). These wings beat too quickly to be used as the right location of signalling marks. In the stinging insects, the elements of aposematic coloration, with black, yellow and red colors, are located mainly on the relatively immobile belly (that can be seen in the flight).

The numerous dragonflies and damselflies can be included into the second group with two subgroups. Fast-wingbeating dragonflies (Anisoptera), with the frequency of wing-beats more than 15-20 beats per second (Rüppell, 1989), form the first subgroup. Slow-wingbeating damselflies (Zygoptera), with the frequency of wing-beats less than 15-20 beats per second (Rüppell, 1989), form the second subgoup Unexpectedly, dragonflies and damselflies have the transparent and decorated wings with signalling color patterns.

For example, aposematic coloration in fast-wingbeating (F = 24-25 beats per second) golden-ringed dragonfly, Anotogaster sieboldii (transparet wings, black & yellow belly) (Ishizawa, 2005), is designed similar to that in the stinging insects.

Finally, the numerous butterflies as well as moths can be aggregated into the third group of insects, which have the slowest beating and decorated wings with the cryptic or signalling color patterns. In these insects, the mean frequency of wing-beats is about 5-15 beats per second (Byrne, 1988). It is important in our context that signalling marks, varied from primitive dots to high quality concentric eye-spots, are most developed just in the group af slow-wingbeating butterflies and moths.

For example, the frequency of wing-beats in large emperor moth, Saturnia pyri, with four eye-spots (Fig.1) is about 8 beats per second ((Byrne, 1988).

Fig.1 (read text)

The detailed analysis of signalling coloration in dradonflies and damselflies allows to select the following 4 basic rules that lie at the heart of signalling coloration in fast-moving natural and artificial objets.

Rule #1. An evolutionarily optimal solution

Signalling color patterns must be bilaterally symmetric (both in the fast-moving and slow-moving objects). It is shown experimentally (e.g., Forsman & Herrström, 2004) that even small asymmetry in size, shape and color impair the effectiveness of silnalling stimuli.

In general, the effectiveness of bilaterally symmetric stimuli is determined by the bilateral symmetry of visual system and visual perceprion evolved during millions of years in the field of Earth gravitation.

Rule #2. An evolutionarily optimal solution

Color stimuli must be located closer to the base of the wings or the center of rotation. These stimuli move with the lower linear velocity than stimuli located at the wingtips.

In accordance with this rule, wings of American rubyspot damselfly, Hataerina americana, have large red spots at the root of the wings (Fig.2). However, H. americana and other rubyspot damselflies (genus Hataerina, Calopterygidae) have, or may have, small red dots at the wingtips.

Fig.2 (read text)

Yellow spots at the wingtips are observed in giant damselfly, Mecistogaster ornata (F = 18 wing-beats per second: Rüppell, 1989), Pseudostigmatidae. In other damselfly of the same family, Megaloprerus caerulatus (F = 7-9 wing-beats per second: Rüppell, 1989), spots at the wingtips are blue.

These and similar deviations of the foregoing rule are mainly observed in the slow-wingbeating damselflies.

Rule #3. An evolutionarily optimal solution

Red colors are rather than blue ones.

The frequency of wing-beats in Easter amberwing dragonfly, Perithemis tenera, is about F = 70 beats per second (Rüppell, 1989). This value is greatest in the dragonflies (Rüppell, 1989), but P. tenera have amber-yellow wings (Fig.3), not blue ones.

Fig.3 (read text)

Wings fully painted in blue (green) colors as well as blue spots at the wingtips are mainly in the slow-wingbeating damselflies.

Rule #4. An evolutionarily optimal solution

Stimuli in signalling coloration of fast-moving natural and artificial objects must be simple. Rounded eye-spots are developed in butterflies, moths (Fig.1) and other slow-flying insects. In dragonflies and even in slow-wingbeating damselflies, these complicated stimuli are absent.

Basic References

Byrne D.N. 1988. Relationship between wing loading, wingbeat frequency and body mass in Homopterous insects. Journal of Experimental Bilogy 135, 9-23

Forsman A., Herrström J. 2004. Asymmetry in size, shape, and color impairs the protective value of conspicuous color patterns. Behavioral Ecology 15, 141-147

Gehres M.M., Neumeyer C. 2007. Small field motion detection in goldfish is red-green color blind and mediated by the M-cone type. Visual Neuroscience 24, 399-407

Ishizawa N. 2005. The response to ratating objects by Anotogaster sieboldii (Selys) males, Pt.2 (Anisoptera, Cordulegastridae). Odonatologica 34, 211-218

Rüppell G. 1989. Kinematic analysis of symmetrical flight manoeuvres of Odonata. Journal of Experimental Biology 144, 13-42

Schön M. 2009. Why birds should communicate by dynamic optical signal patterns and not by the static signals perceived by man. Ethology Ecology & Evolution 21, 161–172

Stojcev M., Radtke N., D'Amaro D., Dyer A.G., Neumeyer C. 2011. General principles in motion vision: Color blindness of object motion depends on pattern velocity in honeybee and goldfish. Visual Neuroscience 28, 361-370

Category: Ethology | Views: 894 | Added by: nickyurchenko | Tags: fast-wingbeating dragonflies, Saturnia pyri, Vespa vulgaris, fast-moving stimuli, wing beats, slow-moving stimuli, damselflies | Rating: 0.0/0





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