New Mass., hamifera fusca hamiferadownloads.hindawi.com › journals › psyche › 1952 ›...
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AUDIO MIMICRY: AN ADJUNCT TO COLOR MIMICRY BY ALBRO T. GAUL Brooklyn, New York During the summer of 1951, while I was working on some aspects .of Vespine wing muscle physiology, I had the .opportunity to study some of the wing sounds of certain Vespine mimics. The work was done at Windsor, Mass., with specimens of Dolichovespula arenaria F. (Vespidae) and Spilomyia hamifera Lw. (Syrphidae). A comparison of the wing tones of these two species has led to the follow- ing considerations. In color pattern, this fly bears a very close resemblance to the wasp, although the abdomen of the fly is somewhat more robust. It is very difficult for me to tell these species apart when they are in flight. Even when the insects are at rest, the longitudinal fuscous band along the wing of the fly makes visual determination difficult without close scru- tiny. It is not known just what, if any, function is served by this likeness; nor can it be definitely determined which insect is the mimic and which the model. It is not a unique relationship between the two genera, since Spilomyia fusca Lw. closely resembles Dolichovespula maculata Linn. in size and color pattern. The original wing experiments involved the use of a microphone and an electro-mechanical transducer to pick up wing beat tones and thoracic vibrations. The output from these instruments was played through a high fidelity preamplifier and amplifier system and was then led into the input terminals of either an audio-frequency meter or an oscilloscope. With either instrument it was possible to measure the wing-beat frequencies of the insects. A direct comparison of frequencies was therefore made between the wing tones of S. hamifera and D. arenaria. The more or less standard wing frequency of workers of arenaria is 82
Transcript of New Mass., hamifera fusca hamiferadownloads.hindawi.com › journals › psyche › 1952 ›...
AUDIO MIMICRY: AN ADJUNCT TO COLOR MIMICRY
BY ALBRO T. GAULBrooklyn, New York
During the summer of 1951, while I was working onsome aspects .of Vespine wing muscle physiology, I hadthe .opportunity to study some of the wing sounds of certainVespine mimics. The work was done at Windsor, Mass.,with specimens of Dolichovespula arenaria F. (Vespidae)and Spilomyia hamifera Lw. (Syrphidae). A comparisonof the wing tones of these two species has led to the follow-ing considerations.
In color pattern, this fly bears a very close resemblanceto the wasp, although the abdomen of the fly is somewhatmore robust. It is very difficult for me to tell these speciesapart when they are in flight. Even when the insects areat rest, the longitudinal fuscous band along the wing of thefly makes visual determination difficult without close scru-tiny. It is not known just what, if any, function is servedby this likeness; nor can it be definitely determined whichinsect is the mimic and which the model. It is not a uniquerelationship between the two genera, since Spilomyia fuscaLw. closely resembles Dolichovespula maculata Linn. insize and color pattern.The original wing experiments involved the use of a
microphone and an electro-mechanical transducer to pickup wing beat tones and thoracic vibrations. The outputfrom these instruments was played through a high fidelitypreamplifier and amplifier system and was then led into theinput terminals of either an audio-frequency meter or anoscilloscope. With either instrument it was possible tomeasure the wing-beat frequencies of the insects. A directcomparison of frequencies was therefore made betweenthe wing tones of S. hamifera and D. arenaria. The moreor less standard wing frequency of workers of arenaria is
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9 Gaul Audio Mimicry 83
150 strokes per second; while that of hamifera is 147strokes per second. This places both tones between D andD#. These readings were made with 42 arenaria workersand 8 hamifra adults. The accuracy of the meter waswithin 1 cycle per second, at this low frequency range. Thevariation in the wing beats was within plus or minus 2strokes per second. Temperature is probably not a factorin wing frequency in insects of this size.With the average wing beat differing by only 2 strokes
per second, or 1.33%, it is apparent that the average per-son, including the author, can detect no significant differ-ence in the sounds produced. Even close attention tosound recordings of the two species cannot show any ap-preciable distinction. It is thus apparent that there is anew form of mimicry, the mimicry of sounds, which inone case at least ccompanies color mimicry.
There is little evidence that the color mimicry of thesewasps and flies serves any particular function. Perhapsthere is common protection against predators, who haveonly to learn .one color pattern. The introduction of soundmimicry into the picture forces us to accept one of twopossible conclusions. Either the similarity of wing toneis a .chance phenomenon, or we must postulate a significantfunction to this similarity .of wing beats. In the latter case,we should further have to. show that certain predators ofSplomyia and Dolichovespula can detect their prey throughsound ranging but are unable to detect the differenceswhich exist between the two sound mimics.
Gaul, A. T. A Relation Between Temperature and Wing Beats.Bull. Brooklyn En,t. Sot., 46: 131-133, 19,51.
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