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Hi all,

Having ventured in to the butterfly rearing world just recently I was looking at some photos I took of some recently emerged Orange-tip larvae and noticed they all had tiny droplets at the end of their hairs.I presume this is normal, does anyone know the purpose of these?
Charlie.

In the Butterflies of Britain and Ireland by Jeremy Thomas it says "It has been claimed that these hairs are really glands, which produce droplets of sweet liquid to attract ants that protect the caterpillars from enemies. If true, this must be very rare in England, for I have examined hundreds of young Orange-tip caterpillars in the wild and have yet to find one being attended by ants, or to hear of anyone who has."

Jon

Thanks for that Jon. It does sound a plausible theory even if it's not true. Maybe it's just the sticky nature of the droplets that deter predators such as spiders from having a go.

It's only in the last couple of years I've really been looking closely at larvae - I've never reared them. But I did notice exactly the same thing earlier this year on a very early instar mountain dappled white caterpillar (a not-too-distant relative). It was nestled deep in the flower head, munching away on buds:



Guy

I have always thought it was an oily substance they secrete that they get from something in their foodplant called glucosinolates and this makes them distasteful to birds and other predators. This substance in some brassicae (brussel sprouts and cabbage being two) is known to make the plant that has it, taste bitter and could do this for orange-tip cats if they secrete it out of their pores. Could also work for similar related species or other species if they eat the same foodplants too.

Glucosinolates contain sulfur and nitrogen and in large enough doses, can be toxic to humans and animals.

I have very rarely (if ever) seen ants attending OT caterpillars