The most effective trapping method

Having read a number of articles on trapping methods and different bulbs, I decided to look at my own data to see which is the most effective type of trap and bulb.  I added up the number of trap events and moths caught using each type of trap/bulb for the years 2009-2011, and came up with an average number of moths per trapping session for each trap.  The figures were remarkably consistent each year.

Trap method                               Events/total moths/average per event
Double Gladiator 2 x 22w actinic       28        660        23.6
40w actinic Robinson                       47      2562        54.5
160w MVBT over a sheet                 67       7593      113.3
125w MV Robinson                        104     13131      126.3

To give some background on the types of traps, the two actinic traps tended to be used more in the off peak seasons, so the numbers might be artificially lower, but even when used in peak the numbers are relatively similar.  

Double Gladiator - 2 circular 22w bulbs, a Paul Batty creation, and most useful when trapping in the garden. Used the least, and tended to be used off season which may reduce the number of moths caught.  Due to being a translucent plastic box, it tends to attract a fair number of moths to the outside walls.

40w actinic Robinson - an upright bulb within plastic vanes, on a home-made Robinson type trap.  This runs from a car battery, and again tended to be used off-peak when it did not warrant staying out overnight. so can be left unattended with a solar switch for the night.  Having a flat top, should not be used in heavy dew, as the moisture collects unwary moths.

I only bought the 160MVBT during 2009, a mercury vapour bulb with a tungsten element added, and used more frequently in 2010, and by 2011 it was used the same number of times as the 125w Robinson.  One of the advantages of the 160MVBT is the fact that it does not require a heavy ballast and control, and plugs directly into the power source, with the disadvantage that it runs even hotter than the 125MV. Of course,  when used suspended over a sheet it requires a flat sheltered location for the sheet.

The 125w Robinson is a standard ALS trap, used by many trappers around the country, and out-performed all of the other methods.  Having said that, the 160MVBT and sheet performs only 10% less effectively than the Robinson, but has the advantage of the catch being visible throughout the night, and would be more useful at a trapping event attended by others.

Photo by Ken Noble

For a proper scientific comparison, I should have 160MVBT on a Robinson and a 125MV suspended over a sheet, but I am happy with the results I achieve, but may consider experimenting further next year..

Although the effectiveness of the various traps are noted above, it should be noted that when a combination of the different methods are used, it can be quite noticeable the different species attracted to the traps.  The different wavelengths of ultraviolet light obviously affect which species are attracted.  I think the mixed combination of bulbs and traps allows greater flexibility to access different habitats at the same site, and also attracts a greater diversity of species.

All the equipment was purchased from Paul Batty http://www.pwbelg.clara.net/mercury/ or Jon Clifton of Anglian Lepidoptera Supplies http://www.angleps.com/.