[Odonata-l] Why report hindwing length

[Fred SaintOurs]

Along these lines, several years ago a co-worker and I developed an easy way 
to accurately measure wing area for insects using a flatbed scanner and 
Adobe Photoshop. Area I believe is more useful than length for most 
analytical purposes, particularly for determining wing-loading for flight 
studies. We never published the procedure, but a few people around the world 
have used it successfully. If anyone is interested I can elaborate.

Fred S


----- Original Message ----- 
From: <aardila at uoguelph.ca>
To: "'Odonata-l'" <odonata-l at listhost.ups.edu>; "Ola Fincke" 
<fincke at ou.edu>; "Nick and Ailsa Donnelly" <tdonelly at binghamton.edu>; "'Mike 
May'" <may at aesop.rutgers.edu>
Cc: <khmo at att.net>
Sent: Monday, March 19, 2007 12:18 PM
Subject: Re: [Odonata-l] Why report hindwing length and not forewinglength 
also?


> Hi everyone,
>
> I have really enjoyed the discussion so far on this subject. I think
> that there is always going to be experimental error (EE) in this type
> of measurements even if there is a detailed protocol. Some initial
> questions to me are: is the current error statistically significant?
> Do mean values of individuals from a given species measured by
> different people vary significantly due to EE? I think that from what
> it has been discussed EE is fairly small (a few milimeters), therefore
> this may not be significant and as Mike hinted it would take too much
> time and unnecessary effort to make detailed (not rapid) measurements
> of every individual. The mean values seem to be fairly close to the
> mean values that can be calculated from NWM and WM. Therefore, I think
> that it may not be necessary to develop a detailed protocol to measure
> wings sizes and body sizes unless it is required for a detailed study
> in which different people are making measurements with a specific
> purpose in mind. The current methods seem to be working well.
>
> I think that some of the most important question are, what is the
> biological significance of all these raw data? Does it matter
> biologically if two people measure the same individual and get
> measurements that differ in 2mm? Does it matter if we think that a
> given species have wings mean sizes of 20 or 18mm? I think that it may
> not matter. I think it may be more important to look at different size
> ranges and go from there. That is for example, to look at Odonata
> species that have wings mean values of less that 20mm, 20-40mm, and
> more than 40 mm, and see if there is anything that these species have
> in common biologically-translating the raw data to a biological meaning.
>
> Then, what about intraspecific variation? That is, body size variation
> within species. There seem to be a lot of factors that influence body
> size in insects. I am only starting to get into this literature, but I
> have read for example that time, temperature and food are usually
> important factors that account for this variation. Also, latitud and
> what it has been mentioned in this discussion seasonal variation. I
> think that seasonal variation encompasses so many factors that there
> is room for multiple studies, if not done before, as to what are the
> most important factors that influence body size variation in Odonata.
> One of them is sex, as Mike mentioned, females tend to be larger than
> males in Damselflies and that is reported in his book with the range
> values for body size. But what about other factors such as food?, for
> example, I wonder if it matters what nymphs eat, Does this have an
> effect on adult body size? Does it matter if there is absence or
> presence of some nutrients in the soil or pond where they live?, the
> same questions apply for temperature and other factors.
>
> So, I think that the discrepancy between measurements may be explained
> and be more important from the biological perspective as oppposed to
> how measurement are done. The EE seems fairly unsignificant. Also, the
> mean values don't seem to differ significantly. If they do vary
> significantly, then we may wonder if the person making the
> measurements made a mistake, or more interestingly, maybe there is
> something really exiting going on at that location with those
> dragon/damsel flies.
>
> Alex
>