What happens when you rub a balloon against a pillow? 

You can pick up a sheet of paper with it afterwards! Not only is this a great party trick, but it is also an example of how creating charge by rubbing two objects together allows you to shortly attract an object of the opposite charge, figuratively picking up a sheet of paper. But what has all this to do with insects? Recently, scientists Sam England and Daniel Robert at the University of Bristol have shown that butterflies and moths take advantage of this phenomenon, and here is how.

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How did they do that?

Moths and butterflies, together making up a taxon known as Lepidoptera, acquire electrostatic charge while they fly. Previous evidence has suggested that bumblebees, honeybees, and even some species of hummingbirds accumulate enough charge to attract pollen onto their bodies, but it was unknown whether this phenomenon applies to moths and butterflies, undoubtedly an important taxon in nature.

The authors wanted to find out if Lepidoptera (butterflies and moths) also carry an electrostatic charge. They allowed the insects to fly for at least 30 seconds and then measured the electrostatic charge they accumulated.

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What did they find?

They found that all individuals that they measured had electrostatic charges, and different parts of the flower had different charges. The charge and, therefore electrostatic field was particularly strong at the part of the plant where pollen is found. They also showed there is enough electrostatic force to lift the pollen granules across an air gap of at least 6 mm! The study also demonstrated that this varies with Lepidoptera (butterfly and moth) families, activity patterns and geographic regions. This was also the first study to show how pollen is moved using electrostatic charge in butterflies and moths. 

Apart from being revolutionary and very interesting, this study also has important implications for how we think about moths and butterflies. Butterflies and moths beat their wings slower than other insects, which could limit their ability to accumulate electrostatic charge. Yet, this paper found it doesn’t. The charge they accumulate is comparable with that of other insects, and electrostatic charge was found among all the measured individuals, irrespective of their activity patterns or geographical origin. This suggests that electrostatic charge is a universal trend among butterflies and moths. Importantly, the study also showed that butterflies and moths are capable of contactless pollination, highlighting just how important pollinators they are (if you had any doubts!). The study also found that butterflies and moths from different families accumulated different amounts of charge, likely relating to their size. The bigger the wings of the insect, the more charge it can accumulate! The differences between Lepidoptera also likely reflect the biogeographical and ecological conditions to which they are adapted. Effective pollination would result in more of that flower becoming available to Lepidoptera. Other pollinating insects can detect electric fields around flowers, thus detecting which recently pollinated flowers have lower nectar rewards. This ability would be highly useful for Lepidoptera, too.  It’s important to understand, however, that the measured charge is likely to be greater if measured in the field! When it comes to bees, their electrostatic charge is greater in the field than in the laboratory, and this is likely the case with butterflies and moths too!

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Are there any negatives to having a higher charge? 

It’s possible that accumulating more pollen would make it more difficult for the Lepidoptera to fly, but this is unlikely to be a big problem, as moths and butterflies visit many flowers, likely depositing the pollen. It is, however, more likely that a high electrostatic charge will make the Lepidoptera vulnerable to predation. Spider webs, for example, are electrostatically attracted towards positively charged insects, and aerial electroreception is widely spread among terrestrial animals. It remains to be determined whether there are any negatives for Lepidoptera for having this higher charge.