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The sweet fragrance of blooming flowers and fresh vegetation isn’t just a seasonal delight—it plays a crucial role in the survival and evolution of butterflies and moths. A new study led by researchers at Penn State uncovers how the daily rhythm of plant scents influences the feeding habits and evolutionary paths of Lepidoptera, the insect order that includes both butterflies and moths.

Published in Proceedings of the Royal Society B, the research explores why some species of Lepidoptera feed on a narrow selection of plants, while others consume a broader variety. The team tested a new theory, the Salient Aroma Hypothesis, which proposes that plant-emitted scents are central in shaping an insect’s dietary specialization.

According to the researchers, plant aromas are more abundant and diverse during the day, giving day-active insects more olfactory cues to locate and specialize in particular host plants. At night, however, plant scent emission diminishes, potentially forcing nocturnal species to adopt more generalist feeding strategies due to the lack of detailed chemical information.

"This hypothesis offers a new way of understanding why some butterflies and moths are selective feeders and others are not," said Po-An Lin, assistant professor at National Taiwan University and former Penn State doctoral student. "It also emphasizes the role of plant volatiles in shaping insect behavior and evolutionary development."

To explore whether scent availability has driven evolutionary adaptations, the researchers compared the antennae—the primary olfactory organs—of 582 specimens across 94 species of butterflies and moths. Working with collaborators at Harvard University, they discovered that female Lepidoptera active during the day tend to have larger antennae relative to their body size than their night-active counterparts.

"This suggests that having more refined olfactory structures is more useful when there are more scents to detect," said Gary Felton, Ralph O. Mumma Professor of Entomology at Penn State and Lin’s research advisor.

They also found that females of specialist species—those that rely on only a few plant types—often possess larger antennae than those of generalist species. These larger antennae are believed to contain more sensilla, the tiny sensory structures responsible for detecting smells, and therefore offer more surface area for odor detection.

"The link between antennal size and dietary specialization was striking," Felton noted. "This enhanced olfactory ability may be a crucial adaptation for recognizing the precise chemical cues of their host plants."

The team’s findings suggest that plant scent availability influences how insects evolve their sensory tools, especially in females responsible for laying eggs on suitable host plants. "This study shows how the availability of chemical signals can shape the evolution of sensory organs," Lin said. "It’s a remarkable example of how plants directly influence the evolution of the animals that depend on them."

To test the hypothesis further, the researchers combined multiple approaches. They first performed a meta-analysis of existing studies and confirmed that plants generally emit more diverse and abundant volatile organic compounds (VOCs) during daylight hours. Then, they analyzed evolutionary relationships among Lepidoptera species and examined the link between daily activity patterns and dietary breadth using statistical models.

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Naomi Pierce, professor of biology at Harvard University and co-author of the study, noted, "Our analyses revealed a clear connection between when an insect is active—day or night—and how many types of plants it consumes."

The results showed that day-active species like monarch butterflies have more opportunities to detect and respond to specific plant scents, often evolving into dietary specialists. In contrast, night-active species such as the Polyphemus moth, with fewer aromatic cues available, are more likely to adopt generalist diets.

"Insect herbivores must make precise choices when selecting plants to feed on and lay eggs," Lin said. "For caterpillars, their survival hinges entirely on the plant chosen by the adult female. Unlike humans who can eat a wide range of foods, many insect herbivores rely on just a few specific plants. The Salient Aroma Hypothesis helps explain why this specialization occurs in some species, while others remain more flexible."

In the world of multimedia, image quality can make or break the viewing experience. But when it comes to biomolecular imaging, clarity is even more crucial—small improvements in resolution can lead to major breakthroughs in understanding proteins, cells, and other biological structures. Now, researchers have introduced a powerful new method that enhances the precision of molecular imaging, opening the door to more accurate insights into molecular dynamics.

Scientists have long used high-resolution imaging to observe single molecules and their nanoscale behavior. However, distinguishing between two fluorescent molecules—known as dipole emitters—that emit light simultaneously from nearly the same point in space has proven notoriously difficult. This challenge has limited researchers’ ability to measure how these molecules are oriented and how they interact, particularly in dense, crowded environments like inside living cells.

A new study published in Physical Review Letters by Matthew Lew, associate professor of electrical and systems engineering at Washington University in St. Louis, and graduate student Yiyang Chen, demonstrates that current polarization imaging techniques cannot differentiate between two coincident dipole emitters and a single molecule. This limitation arises because the emitted light patterns are mathematically indistinguishable.

To overcome this, Lew and Chen combined two complementary techniques: they manipulated the polarization of the laser used to illuminate the sample and measured the polarization of the emitted fluorescence. By fusing these two approaches, they created a method that successfully distinguishes between one and two molecules, even when they are extremely close together.

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This new technique significantly improves measurement precision. It enhances the accuracy of dipole orientation detection by 50% and boosts the precision of angular separation measurements between molecules by up to four times compared with traditional methods.

“Structure always determines function,” Chen explained. “The behavior of cells is governed by the shape and orientation of proteins and biomolecules. For example, antibodies and viral antigens must align in a certain way to interact—these small details at the nanoscale influence how the entire system functions.”

Initially, the researchers assumed existing polarization microscopes could resolve two nearby fluorescent molecules by analyzing the polarization of their emitted light. But their calculations showed otherwise. Dipole pairs produce the same light pattern as a single rotating dipole, making them indistinguishable using standard methods.

By introducing polarized illumination into the equation and pairing it with polarization-based fluorescence detection, the team was able to break through this limitation. Their integrated method generates distinct images for single molecules and molecule pairs, enabling clearer and more precise measurements.

“This represents a big leap in a well-established field,” Lew said. “Traditionally, scientists treated fluorescent molecules as simple point sources because it was easier. But at the nanoscale, treating molecules as dipoles—objects with both direction and intensity—is critical for accurate analysis.”

He added that biological molecules aren’t shaped like perfect spheres, and their interactions depend on how they’re oriented. The team’s new imaging method allows researchers to measure these orientations and protein conformations more precisely, which has far-reaching implications.

The approach could dramatically improve our understanding of dynamic molecular processes, especially in live cells where real-time observations are essential. Lew believes this technique could ultimately advance research in areas ranging from protein behavior and drug development to disease diagnostics.

“To move science forward, the details truly matter,” Lew said. “And now we have a new way to see those details more clearly than ever before.”