Use salt to attract butterflies.

Western tiger swallowtail obtaining salt.

All living things need salt.  The minerals sodium, potassium, and chlorine are essential nutrients that allow our cells, organs, and organ systems to function properly.  Although these minerals are present in all foods to some extent, the concentration may be insufficient to meet the organism's needs.  In the case of butterflies, the adults feed only on nectar which does not have enough of these important elements.  They can supplement their diet by consuming salt wherever they may find it.

This should not be considered unusual.  We supply farm animals with salt licks to augment what they get from their food.  Salt tablets are commonly taken by people who experience long periods of heat; our bodies sweat to cool us down but we give up salt in the process (also a bit of urea - that's a comforting thought when you get sweat in your eyes).  Dogs are very fond of salt and are much more likely to lick you if you happen to be sweaty (they don't care about the urea in your sweat).

A common place for butterflies to take salt is on roadsides.  To prevent ice buildup on roads trucks spread sand and salt.  Crushed raw salt is often used and contains many of the nutrients that are in short supply.  Even sand will have a certain amount of salt in it.  If you see a butterfly on the side of the road it may just be resting, but it could also be looking for salt.

So, what do they do when road salt is not available?  Clearly, butterflies managed long before we showed up to offer a saline solution for them.  It turns out there are other sources.  Puddles and muddy banks often have some salt present.  I have seen a dozen butterflies extending their feeding mouthparts trying to take up salt-laden moisture from these damp reservoirs.  Another less palatable find are dead animals.  Body fluids carry a lot of salt with it; if you cut your finger and put it in your mouth there is a salty tang to it.  That's the salt in your blood.  Our blood carries just under 1% salt by weight.

Caterpillars don't need any extra salt.  They consume vast quantities of vegetable matter and get all the salt they need.  The adults take sugary snacks that are relatively high in energy but low in other nutrients.  One way to attract the adults is to put out damp sand infused with regular table salt.  Butterflies will find it and stop by for the gracious offering.  It's not a gift to give to a loved one, but the butterflies will appreciate it.

Thanks for reading.   www.ericspix.com   Eric Svendsen