The Suffolk Argus
November
- tzon
In Suffolkfor example,we are mainly concernedwith TL and TM with which map referencesareprefixed. The sidesof each I 00km squareare then subdivided into 100 points I km apart, measured.from the south-westcornerof the square eastwards(eastings)and northwards(northing,). Theparallel grid linesjoining thesepoints and marking out 10,000 squaresof 1km sidesarefamiliarly numberedon the map margin which we use to identify a particu/,arpoint. Blocks of four I km squares representa tetrad (2km x 2km cover the same area).
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In response to a number of interesting questions which were put to us by keen visitors to the Suffolk Show we thought that a 'Questions and Answers' spot might usefully become a regular part of this magazine. To start us off, here are three Questions that were put to us which will hopefully be of interest to all our readers.
National atlasesoften disp'4y recording units of I 0km squareswhich contain 25 tetrads (5 acrossand 5 down). Regional atlasessuch as Mendel and Piotrowski (I 986) The Butterfliesof Suffolk, The Suffolk Naturalists' Society,are usually plotted by tetradsbut with the actual data gathered by I km squares.The recordsfor The Millennium Projectwill beformu'4ted in a simi'4r way, national recordingby I 0km squaresbut with Suffolk recordingby 2km squares.
QI. What exactly is a tetrad and why is su~h a measurement used to record butterfly sightings?
A.
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Let'sgo back to squareone so to speak and briefly reviewthe National Grid systemwith which we should all at least befamiliar due to the excellentseriesof 1:50,000 OrdnanceSurvey maps( those with the magentacovers!).The National Grid systemis broken down into squareswhich get progressively smaller. They begin with 500km squares(identified bysingleletters} which are then divided into I 00 km squares(identified by the 500 km squarektter plus a farther letterof the alphabet,excluding T).
Q2. What are the black and red butterflies we have been seeing? We cannot find any descriptions in our butterfly book.
A.
Interestingly,more than oneperson took the time to describetheir observations. It_soonoccu"ed to us that the descriptionswereeither that of Cinnabar or Burnet moths. From the descriptionsand thefact that we were being told that thesesightings had occurredduring the previous two weeksi.e. the last two weeksof May, it
1995
late-leaving visitors whose attention had been attracted by finding plants placed under their very noses as they streamed out. What a good idea it was to put them outside. By 6.30 pm we had packed away, James now finding himself custodian of the display material. During both days we had many visits from friends new and old and we rarely had a moment when we did not have someone at the stand. Our old friends came to chat and give us support. Our new friends, who we hope will become old friends, asked all sorts of questions and showed great interest in what we are trying to achieve. Special thanks must go to The Suffolk Naturalists' Sociery for allowing us to share their space and for bearing with us and lending a hand on that first morning. To Roger Kendrick for providing tables and chairs. To Paul Gilson for supplying many of the plants and to Paraphernalia of Westleton for providing the watering can and transport. Indeed thanks to all involved in what turned out to be a very successful show. Hopefully, in the years to come ., we will be able to welcome many more";' of you in helping us to promote our cause. It really is an enjoyable experience.
As well asproviding an interestingview of thisyears'show, this reportdemonstratesthe hard work and effort requiredto make such an event a successas well as the true value of'a dedicatedgroup of enthusiasts.If you feel able to help in any way next year pleasecontact any member of the committee. They will be delightedto hearfrom you - Ed.
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