Question from Sam asking what bug this is and why it has a fluffy butt. May 2020.

@Earth2Meekus asked about these on Twitter. May 2020.

Spring and summer time bring out all the interesting bugs! Over the years (and recently) we’ve had a few people ask what these insects are and why they have “fuzzy butts.” These insects are broadly called planthoppers. Why do they have these fluffy projections out of their abdomen? Let’s look closer at their group.

A good place to start when trying to identify an unknown insect is its order.  For example, beetles have hardened forewings and are in the order Coleoptera. These fuzzy butt critters have distinct sucking mouthparts (think of a drinking straw) which place them in the insect order, Hemiptera. Hemiptera are called the true bugs. There are many bugs within the group, such as planthoppers, stink bugs, assassin bugs, cicadas, aphids, scales, and more. Hemipterans are hemimetabolous, meaning that they have incomplete metamorphosis. Hemimetabolous insects do not have a pupal stage from larva to adult. Each molt looks pretty similar from the first molt to the final molt to the adult form. The immature stages of these insects are called nymphs.

Within Hemiptera are the Fulgoromorpha – the planthoppers. There are many species in this group. Some are considered pests because these bugs feed on phloem tissue of plants. An interesting characteristic of the group is that many nymphs and some adults have these “fuzzy butts.” A species of planthopper from Australia, Scolypopa australis, commonly known as the passionvine hopper, nymphs are referred to as “fluffy bums.” Anecdotally, where I currently live (Texas), I’ve also heard and seen people refer to the nymphs of some planthoppers as “fuzzy butts.”

An example of a planthopper with wax-projections – Wax-tail hopper 
Fulgoridae: Pterodictya reticularis
Photo by: Geoff Gallice from Gainesville, FL, USA

The dorsal plate segments of planthopper’s abdomen produce wax from special glands. These waxy projections are hydrophobic (i.e., can repel water). This is thought to help these critters by repelling water and other liquids excreted from them. As previously mentioned, these insects are phloem feeders. The way I’ve heard it before goes something like this: imagine duct taping a straw to your face and piercing it into a fire hydrant and you need to keep drinking for hours to get sufficient nutrients. That’s a ton of pressure. This means that planthoppers are constantly drinking a lot of sugar water from the plant they are feeding on. Thus, they need to excrete a lot of that sugar water to get the proper amount of nutrients from the plant without bursting. The way they get around this, simply put, is by pooping out sugar water. Some other plant feeding groups in Hemiptera, such as wooly aphids and whiteflies, also have waxy secretions because of the nature of feeding on phloem.

There are other speculated uses of the fuzzy butts –hiding from predators and gliding. Check out this video showing an example these behaviors!

Tl;dr

These bugs with “fuzzy butts” are planthoppers and have the fuzzy butts because they are waxy projections that help repel pooped out sugar water. And perhaps have other uses such as predator avoidance and gliding.

What a beautiful photo! Shown are flatid leaf bugs adults and nymphs (Phromnia rosea), in Ankarana Reserve, Madagascar
from Sharp Photography, sharpphotography.co.uk

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