Even though they only drink liquids, butterflies don’t technically pee or poop. They simply lack the needed organs like kidneys to filter and concentrate urine.
However, if they drink too much liquid, they have the ability to create a fine mist of liquid from their abdomens. This has been seen with many species of butterfly and is usually associated with being actively mudpuddling.
Butterflies have a very interesting physiology that allows them to be at their attractive best while flying for hours in the heat of summer.
In this article, we will talk about the abstract world of butterfly hydration, including where these insects want to stop for drinks!
Butterflies Release Water from Their Abdomens During Mudpuddling
If you happen to catch some butterflies gully bottoming or mudpuddling, you may see them release a fine spray, droplets or bubbles of water from their abdomens while drinking.
This dew is commonly released through an anal open in the second terga of the lower abdomen. This jet of liquid can easily be mistaken for urination and is noted in a lot of butterfly species.
Scientists and wildlife photographers have recorded this forceful liquid expulsion, termed abdominal dew or abdominal sap from the tip of the abdomen, while butterflies are taking huge doses of nutrient and mineral enriched fluids the butterflies covet.
Sometimes: The fluid release is slower leaving a sticky, sap-like liquid forming a droplet at the tip of the abdomen. This “urination” phenomenon has also been observed in butterflies after aggressive flight and in humid conditions.
The Fluid Released by Butterflies Varies Massively in Size and Consistency
If you look closely enough at excreted fluids, there may be some differences in droplet size size.
The size of the liquid formed into droplet while being ejected from butterflies has nothing to do with the size of the butterfly because even small butterfly species produced large droplets that were disproportionate in size.
The fluid may also differ in colour and form. The liquid can be identified as clear or muddy and cloudy.
It is assumed that the liquids the butterfly consumed before excreting, the amount of time of feeding and how long the butterfly remains to digest its meals all affect the properties of what the droplet will be like.
Why Are Butterflies Releasing Fluids in This Way?
We don’t exactly know why butterflies excrete liquid in this manner and scientists are still researching this.
The liquid has yet to be fully characterized, but they don’t think it is simply water.
Several hypothesis have come up from entomologists who study butterflies such as:
- Condensation takes place on the butterfly’s abdomen causing a fluid build up to the distal end of the abdomen which eventually drips from the end.
- An evolutionary adaptation from an aquatic ancestor
- A homeostatic process
- The butterfly is discharging an unnecessary excess of liquid which could have negative effects on flight; presumably the liquid was too heavy.
- The butterfly places priority on absorption of the salts and other nutrients for hydration, discarding the excess liquid.
Butterflies Simply Do Not Have the Sophisticated Systems for Fluid Balance That Humans Do
But they still require the same fluid need, frequently in difficult environments where fluid may not be plentiful.
Their need for moisture, salts and other nutrients can cause wild fluctuations in the concentration and composition of body fluids as they drink any number of fluids.
Thus, butterflies have to depend on simple approaches to changing their body water composition including:
- ingestion
- osmosis
- diffusion
- evaporation
- excretion
Butterflies Are Reliant on Their Tube-like Digestive System for the Majority of Their Fluid Exchange
The basic digestive system of a butterfly is where most of the fluid exchange is going to happen.
Inside its abdomen the butterfly has a crop, midgut and hindgut for absorbing all the fluids that is sucked up through its long straw-like proboscis.
Those “pee” Droplets Are a Big Part of How Butterflies Drink
Like more than half of the insect species around the world, butterflies are fluid-feeders.
The butterfly’s tube-like mouthparts provide a long channel for fluid, which is ingested, to flow up to the butterfly’s head.
Research conducted by Kent State University using X-ray imaging and optical microscopy revealed that butterflies are able to uptake fluids by capillary action, making use of liquid films and the surface tension of those films in what they are looking for to feed.
It is even further understood that other types of feeding have four steps:
- Wetting
- Dewetting
- Absorbing
- Pumping
Many butterflies will regularly recycle their waste material.
The wetting process can be used to interact with dried things, like bird poop, where the butterfly will arch its abdomen out and push out a drop of fluid with the sole purpose of wetting the faeces so it can feed off of the moist material.
This behaviour, now described for the first time, is used for the length of feeding.
The butterfly’s proboscis and mouthparts are both fibrous and porous. They are adapted to performing fluid-filling and sucking back liquids.
The physical exertion performed by a butterfly in fluid-feeding is muscle work to move liquids into its digestive system.
Rounding Up
This new excretory behaviour in butterflies is incredible to witness and is an indication that the butterfly is able to take a good drink of their chosen liquid safely for an extended period of time.
The appearance of these water droplets is usually strongly connected to mud puddling.
Have you heard about this feeding behaviour in butterflies? It is not for the squeamish as it involves butterflies gorging on blood, dung, and even corpses.
If you want to find out more, why not read the article “Do Butterflies Drink Blood?”