Discovering the Body of Butterflies
by Regina Cutter Edwards
The body form of a butterfly is like no creature in the world. They are beautiful flying animals that have unique characteristics that are unlike any other. As for an insect, they have an exoskeleton with jointed legs and three basic body parts; head, thorax, and abdomen, but the more distinctive characteristics of a butterfly are much more impressive. Butterflies are sometimes known as flying gems because of their beautifully colored wings. If you have ever wondered why the wings appear as they do or how butterflies search and find specific flowers, this is the article to read.
Butterflies have two different types of eyes, single and compound. The one pair of simple eyes, ocelli, are single chambered and are primarily for determining light brightness. They are unable to focus on an individual object. The compound eyes are multifaceted and are used for their main eye sight. The light comes through one facet and is received by one rhabdom, similar to human retinas. Butterflies are able to see light wavelengths from 254 to 600 nm, this includes ultraviolet light, a light that we are unable to see. People can see only 450 to 700 nm. Flicker-fusion rate is the rate at which the light flickers to form a continuous image. For butterflies to see while flying their flicker-fusion rate is up to 250 times higher than it is for people. Our flicker-fusion rate is between 45-53 flickers per second.
Butterflies have a siphoning-sucking mouthpart structure, a proboscis. It is similar to a long tube and coils up underneath the head of the butterfly. In the center of the proboscis there is a food tube through which the nectar is siphoned. Along two sides of the food canal, there are small muscles that control the coiling and uncoiling of the proboscis.
Butterfly’s have one pair of segmented antennae. The basic shape is clubbed, meaning the segments increase in size as it gets further away from the head. For butterflies, this usually creates a club like appearance on the tip of the antenna. Butterfly antennae have chemoreceptors that are used for assessing the environment’s physical and chemical properties. Chemoreceptors are similar to the taste buds on our tongues. They are open nerve endings that transport the information to their central brains for translation. For example, butterflies use their antennae to detect which plants are producing nectar and males can sense pheromones from females of the same species.
Near the base of the antennae, in the second antennal segment, there is also a very important organ called Johnston’s organ. It is used for balance and orientation during flight. With an antenna lacking, butterflies may be unable to fly in a particular direction and may end up flying in a circular pattern.
Butterflies have beautifully colored wings that appear to be every color imaginable. They are covered in hundreds of thousands of tiny scales. The colors are determined by the layering and overlapping of the scales. These colors offer many benefits to the insect; they assist the butterfly by either camouflaging or by warning colorations that deter potential predators. Many butterflies also have ultraviolet colors on their scales as well. Although people cannot see these colors, butterflies can. Many times they are able to distinguish sexes by these additional colors on their wings.
Butterfly wings often exhibit melanism, the darkening of wings, veins, or wing scales and this assists with thermal regulation. Butterflies are ectotherms, needing external sources to warm them. Butterfly wing veins are hollow and hemolymph, the insect’s blood, is able to circulate through the body. When the temperatures are cooler outside butterflies are able to warm quicker with darker colorations.
Butterfly wings are hydrophobic, meaning they repel water. The microtopography on the wings allows water molecules to easily roll off the surface. This has an additional benefit, when water is repelled it works as a cleaning mechanism. Dirt that is collected on the wings and can inhibit flying is removed along with the water; it helps keep the butterfly’s wings clean.
Butterflies have six jointed legs and each leg has six parts; coxa, trochanter, femur, tibia, tarsus, and pretarsus. The tarsal segments at the ends of the legs have chemoreceptors which are important for the butterfly to smell and taste. A female butterfly is able to determine if a plant is suitable to lay eggs upon by the chemical released from the plant after drumming their legs on the leaf surface. The chemoreceptors only pick up certain chemicals, which are genetic. For example, a Monarch butterfly will respond to the chemical release of certain milkweed plant species by laying eggs, but will not lay eggs on a snapdragon plant like a Common Buckeye. Butterflies are also able to locate food sources by using the chemoreceptors in their legs.
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