October is the heart of autumn in many parts of North Amreica, with intensifying colors of fall foliage. Insects reflect the changing hues of plants, the better to camouflage themselves. As chlorophyll recedes, xanthophyll (yellow) and other carotenoids (orange), begin to manifest. Anthocyanins (reds to purples) become prominent, too. Could it be that insects feeding on those leaves take on the same colors? Perhaps the insects are merely responding the shrinking period of daylight as the leaves are doing.
This year, here in northeastern Kansas anyway, an exceptionally dry summer has resulted in subdued fall colors. Green leaves persist, even if they are withered from a record-breaking hard freeze last week. Some insects insist on being wholly green, or at least partly so.
Beige is an overwhelmingly common color of fall in pastures and fields, and even lawns thanks to our current drought. Insects of the same color merge seamlessly with grasses and weeds, becoming nearly impossible to detect unless they move. On windy days it is even more of a challenge. Thankfully, for entomologists and bugwatchers, insects frequently alight on, or are blown onto, sidewalks, the sides of buildings, and other surfaces where they stand out.
Many insects with warning colors are bright yellow, and black, regardless of the seasons, but in autumn they complement the colors of plants.
Orange and red are less common colors in insects, and often part of the loud wardrobe of aposematism (warning colors), or mimicry of other insects that are well-defended by venom or toxins. Lady beetles defend themselves by autohaemorrhaging, or “reflex bleeding,” from leg and body joints. An alkaloid toxin in the haemolymph is aromatic and sticky, quite repulsive to would-be predators.
Many insects are iridescent, often vividly so. Whereas the preceding colors are expressed by pigments that absorb all wavelengths of light except the one we interpret as brown, beige, green, yellow, orange, or red, or black, iridescent colors are produced by a different mechanism. These structural colors are rendered by micro-sculpturing, and/or layering, of the cuticle of the animal’s exoskeleton. Light bounces and reflects, and the color we see varies depending on the angle of the light hitting the organism.
A few insects are white, or appear so at least. This is especially the case for true bugs that exude waxy secretions to protect themselves from desiccation and make themselves distasteful to predators. Leafhoppers display almost every color combination imaginable in patterns of spots, blotches, stripes, bands, and speckles.
Keep looking for colorful “bugs,” deep into fall. Some will enjoy your rotting Jack-O’-Lantern. Others will find their way indoors, preferring the same comfortable climate you yourself enjoy. Meanwhile, I will do my best to keep cranking out blog posts to help you identify them. Stay warm and dry, friends.