wing beats

I have been making recordings of various flying insects.  Although each tends to produce a range of pitches, depending on what they are doing, they do all appear to inhabit their own peculiar pitch territories.  Interestingly (so far at least) I have found that these pitches do not appear to be evenly spread over the frequency spectrum but instead sort themselves into groups.

So far, the lowest pitch belongs to the macroglossum stellatarum which emits a fairly constant low E (one stave below the bass clef).  This is shared by the libellula depressa who also hovers around this note, but with more clackety wing noise.  Up a minor third is the xylocopa violacea (on a G) and sharing its pitch territory with the phyllopertha horticula (on an Ab) and the vespa crabo (on an A).  Up a further augmented fourth is the bumble bee (as yet not identified - there are about fifty different species!) which seems to buzz around Eb, and up another major third is the apis mellifera.  Finally (so far!) there is the bombylius major buzzing on a Bb (resting on top of the bass clef) and the vespula vulgaris on a B.

From knowing the pitches of the various buzzes, it is possible to then estimate the number of wing beats per second.  Hence my recorded insects were beating their wings in the range of around 40 times a second for the libellula depressa and about 250 times per second for the vespula vulgaris.  Apparently this increase of wing speed as the insects get smaller is because aerodynamic performance decreases with size, and so to compensate they have to flap faster.