Perhaps butterflies are not as nice as you think.

An article lifted from The Guardian newspaper, today 29th September. This newspaper is at the forefront with environmental articles and, at least, a scan of their articles is worthwhile. The are UK and worldwide editions.

Why the copy? I believe it offers a new insight into the world around us. Generally we see butterflies as the attractive, good-guys of the world. But, like most organisms they can have a darker side.

Occasionally a similar milkweed species arrives in the UK. Milkweeds are quite common on the west coast of USA. I have encountered two hibernation groves in central California.

Also, it is worth noting that male butterflies fight over access to females, and you will spot this in your own gardens. Generally butterfly males fly in vertical circles around a potentially receptive female in a pre-mating dance wafting sex pheromones in her direction. How the females decide to mate or to ignore the male is a mystery to me. Information please!

Now, all thoughts of sex are probably on hold for surviving adult UK butterflies as they stock up with resources before the overwintering species prepare to hide away in hibernation. Other species will spend the winter as eggs or underground as larvae.

I delay cutting some parts of my wild meadows until I can be confident that insect larvae are safely underground. It is also delayed to ensure slow worms have hibernated (they can be killed during the cutting process) and to give some space for the short-tailed voles.

The article:

The butterfly that drinks caterpillars alive to bolster its pheromones

Milkweed butterflies in Indonesia have been discovered to supplement their diets with the juices of larvae

Two orange butterflies on purple flowers in a green field
While butterflies usually feed on nectar, males may supplement their diet with other chemicals to produce mating pheromones Photograph: Scott Gaulin/AP

The complexity of insect behaviours is a frontier we have barely explored. As conspicuous, charismatic creatures, butterflies get more attention than most, and yet there is still so much to discover.

Adult butterflies usually feed on nectar, although some, such as male purple emperors, enjoy the minerals from muddy puddles and animal turds. But milkweed butterflies in North Sulawesi, Indonesia, have been discovered to feed upon live, dead and dying caterpillars.

A red admiral on a buddleia
UK’s Red Admiral butterfly. Does it too have a darker side?

To produce mating pheromones that attract females, male butterflies may supplement their diet with other chemicals. Usually these are obtained from plants but the milkweeds have been observed scratching caterpillars and apparently imbibing their juices with their proboscis.Advertisement

“The caterpillar larvae would contort their bodies rapidly in what appeared to be futile attempts to deter the scratching,” said Yi-Kai Tea from the University of Sydney, who observed this never-previously-reported behaviour with colleagues.

Even stranger is the fact that the milkweed butterflies are feeding off similar caterpillars to their offspring – not their own species but from their own subfamily.

Like all good scientific discoveries, this “kleptopharmacophagy” – chemical theft – only raises further questions.

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