(Image credit to Bernd Schllhorn, Serge Berthier).
Scientists discovered fluorescent green wasp nests while trekking through tropical forests in northern Vietnam.
These nests look like clusters of hexagonal cells and were constructed by several species, all of which are part of the genus Polistes. The cocoon caps, made from silken fibers and sealing the hexagonal cells' undersides, protect the nest's growing larvae. These cocoon caps, for unknown reasons, emit a strong greenish-yellow glow if exposed to UV light at 360 to 400 nanometers wavelength.
Bernd Schllhorn (a senior author and professor of chemistry at University of Paris) told Live Science via email that "we were very surprised to discover such strongly fluorescent biomatter."
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(Image credit to Bernd Schllhorn, Serge Berthier).
In order to find unknown fluorescent insects in tropical rainforests the team set out initially. They then purchased UV LED torchers. Schllhorn stated that they were not looking for nests of wasps. "This phenomenon has never been documented in the past by scientists nor photographers," Schllhorn stated.
The nest cocoon caps become bright white when exposed to white light. The nest cocoon caps begin to glow bright white under normal daylight. At night, the bright green glow of the nests is visible up to 65 feet (20 m) away when the UV torch is used.
These nests were compared to the nests of two other Polistes species, one from the Amazonian rainforest in French Guiana and one that is from a temperate area of southern France. The researchers found that all of the wasps' cocoon caps had similar fluorescent properties. However, the intensity and range of UV light that produced the strongest reactions varied.
Researchers now wonder if the fluorescence is a special function for wasps after discovering these glowing nests. They have several theories.
The glowing nests may act as a homing beacon for wasps returning to their nests at night. Or perhaps different species of wasps use subtle fluorescence variations to distinguish their colonies from nearby ones. The fluorescent cocoon caps may protect the larvae from UV rays, which could otherwise cause damage.
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Studies have shown that wasp larva development can be heavily affected by the length of the day. The glowing cocoon caps could help regulate how much sunlight reaches larvae and make them more productive as pupae. Schllhorn said that the last hypothesis was his favorite.
The Vietnamese Polistes species breeds during the rainy season between June and August. This is when clouds block a lot of visible light from reaching their nests, but let a fair amount UV light through. The study authors noted that the residual UV light from the cocoon caps may influence how wasp larvae grow by increasing their exposure to light during development.
The authors plan to study the chemical structure of the fluorescent compounds contained in the nests. The authors also intend to determine if the compounds could be used in medical research and biological research. For instance, fluorescent compounds can be used to label molecules within the body.
Original publication on Live Science
