[Syrphidae] proboscis length

[Francis Gilbert]

hi everyone

In Lesvos during the discussion of my talk I suggested that two vital traits of adult syrphids could usefully be incorporated into the Syrph the Net database of species: a measure of body size, and proboscis length. I believe that Axel is working on doing providing some data for existing measurements of proboscis length. Gerard commented that everyone needs to know how to measure proboscis length on their specimens, so that a comprehensive set of data can build up.

Here's a pretty easy way to do it. Measure the length of the prementum, the sclerite forming the underneath of the gutter that ends in the labella (see attached figure). It is usually visible even on dried specimens where the proboscis is retracted into the head, but just as with the genitalia, you could relax the specimen and tease out the proboscis with forceps to expose the prementum.

Once you have the prementum length (PR), then the proboscis length (PL) is:

PL = 4.8 x PR

This relationship is linear with a very high correlation (r² = 0.991 - see below), and hence is a reliable way of estimating proboscis length on a dry specimen, otherwise tricky or impossible to do.

[cid:image001.jpg at 01D6F7C2.1C99B5C0]

Best wishes

Francis



Professor Francis Gilbert
Room B132 Life Sciences, University Park
University of Nottingham, NG7 2RD, UK
Tel 0115 951 3215
webpage: www.nottingham.ac.uk/~plzfg/<http://www.nottingham.ac.uk/~plzfg/>

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