Thursday, July 21, 2016

Feeding Attraction Tests (initial results)

VERY encouraging initial general (feeding) attraction test results today, from a site in France and also from here at Fermyn last week. Although the test in Fermyn was only a short 15 minute stint, the feeding attraction mixture still easily managed to bring 2 males and 1 female down from the canopy. The attached photo shows the results from a similar test performed at a site in France today.

As everybody here is fully aware, females rarely ground, but exposure to this compound mixture certainly appears to help achieve this. I posted some GC-MS data of an Oak sap sample here last July which showed the consistent occurrence of a series of volatiles (red arrows) which varying only in chain length. The feeding attractant compound currently being tested simply contains a mixture of just 4 of these compounds which are highlighted with the 6, 8, 10 and 12 numbered Carbon chain lengths on the GC-MS trace file. It is proposed that the compounds work in a synergistic manner, so the more of them there are the better the response is expected to be. Considering this encouraging result I will therefore now order more of these compounds in the hope for an even better and more absolute result next time around.

It should be noted that this mixture is very different from the male only attraction compound and simply attracts the specimens to a preferred food source.


dennis said...

it may not only be the volatile components that are important attractants; if involatile components also play a role, then LC-MS could be used too?
Dennis [retired analytical chemist!]

irisscientist said...

Dennis, if any compounds were involatile then they would obviously not function as attractants. Agreeably this does not however mean that such compounds are not also important. When imbibing, Apatura (like many other butterflies) dip their antennae to actually touch the feeding material, as if to literally 'taste' the feeding substance. In additional many female Nymphalidae species scratch at leaf surfaces using their additional clawed tarsal segments (on their vestigial front brushes), again as if to actually 'taste' the leaf and test for oviposition compatibility prior to laying.