Scientists say the oriental hornet has a special pigment in its abdomen using which they can harvest solar energy and be more active in hot weather.
According to a report published in the journal Naturwissenschaften, this unique ability also explains the large yellow stripe across the body of the large wasp species.
The discovery provides a good reason why hornets become more active as the day gets hotter and sheds light on the way that the insect's metabolism works.
Scientists at the Tel Aviv University found that oriental hornets (Vespa orientalis), which range from the Near East to India, are most active in the middle of the day.
Led by Dr. Marian Plotkin, the team also observed that Oriental hornet workers correlated their nest-digging activity with the intensity of sunlight. They therefore decided to test a theory suggested by the late Professor Jacob S. Ishay who said the species might be able to harvest solar radiation.
Using an atomic force microscope, the team examined the hornet's cuticle structure and found that the brown part of the cuticle is made from an array of grooves, with a height of just 160 nanometers.
The yellow part of the hornet's body, however, has a different structure made from a series of oval-shaped protrusions, each containing a pinhole-sized depression.
"The pigment melanin gives the hornet its dominant brown color,” explained Dr. Plotkin.
“The pigment xanthopterin, in the head and abdomen in a form of stripes and bands, gives the Oriental hornet its bright yellow color."
"Xanthopterin works as a light harvesting molecule transforming light into electrical energy," she explained.
Further tests revealed that the 50nm tall protrusions stop sunlight from being reflected off the hornet's body and trap it inside the insect instead.
The brown part of the insect's body has the best anti-reflectance properties, helping to split any sunlight that falls upon it into several beams travelling in different directions, the state-funded BBC reported.
The cuticle also contains a thin sheet-like structure which has a series of sheets stacked on top of each other.
The thickness of the sheets decreases from top to bottom and every layer contains rod-like structures stacked together composing chains of a polymer called chitin. The rods are embedded in a protein matrix.
This intricate structure further contributes to keeping sunlight within the cuticle, forcing it to bounce between different layers.
"We assume that some of the energy is transformed in a photo-biochemical process which aids the hornets with their energy demanding digging activity," said Dr. Plotkin.