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The lepidopteran

This is the last stage of the lepidopterans metamorphosis and is called adult or imago. A lepidopteran can’t moult or grow larger, all energy is used for its primary objective and that is producing and spreading offspring.

The wings

When the butterfly has emerged and the moth squeezed itself out of the soil or cocoon, it's time to inflate the soft and tiny wings it still has. After finding a suitable place in the immediate area where the lepidopteran can hanging freely, liquid from the abdomen is pumped into the hollow veins of its wings. By pumping up its wings, they will be enlarged more than a dozen times. After that is done, the lepidopteran has to sit still for a while to let the wings and exoskeleton harden. This process may vary depending on the species and size by twenty minutes till more than an hour. Once the wings and skeleton have hardened, the size and stiffness of wings and body remain preserved. Liquid from the wings is now led away, that ensures the wings will be lighter and makes it easier to fly. Because the fluid is not of use anymore and the body has hardened as well, there is not enough room left. The excess fluid is excreted together with accumulated waste during pupa stage, the weight loss will make it easier to fly.

The wings are made of hollow tubes/veins with membranes in between. These membranes are transparent and covered with tiny coloured scales that overlap like roof tiles, this is why the membranes are seldom visible. Because of the different colours and patterns of scales, there is an infinite number of variations, the top and bottom of the wings often have a completely different pattern. The difference between one and the other species are mostly easy to recognize by the pattern of their wings. A lepidopteran has no constant body temperature like we have, to be able to fly the temperature has to exceed a certain level. Butterflies warm up their body by collecting heat from the sun through their wings, this heat is absorbed by the thorax and body/muscle temperature will increase. Because moths usually can’t benefit from the sun's heat, they found another way to raise their body temperature. By vibrating their wings back and forth, muscles will start producing heat in the thorax. Before taking off, you will see a moth vibrating its wings, when the body temperature is sufficient it will fly away. The Latin name for butterfly or moth is Lepidoptera (scaled wings) because of the scales on their wings.

The head

During metamorphosis, a lot has changed, the head of the lepidopteran is quite different from that of the caterpillar, the lepidopteran that has two segmented antennae which are clearly present. The shape of the antennas is a good guide to tell butterflies apart from moths, butterflies have long, thin antennae with a thickening at the end. Many moths have feathered antennae, those of the male moth are generally wider than those of the female, there are threadlike antennae that are wider than those of butterflies and don’t have a thickening at the end. Antennae contain the smell sense of moths, male moths use this to scent pheromones released by the females. Their scent is well developed and males will start flying upwind when just a couple of pheromone molecules are detected, most moths can scent a calling female moth form many miles away. At the bottom of the antenna in the second segment a vestibular is present, it allows the moth to orientate and maintain balance in flight. Some species of lepidopterans are able to hear with their antennae. Detecting noise isn’t strange in the lepidopteran world, till now four different hearing organs are known, this is just one of them.

The sight of the lepidopteran is not very good. With its compound eyes, movements can be detected without any problem but a clear images can’t be created with this type of compound eye. Colours can be detected very well at visible and ultraviolet range, this helps the butterfly to find food. Furthermore butterflies use their sight to find a partner.

Not all moths take food throughout their lives, some don’t have full developed mouthparts. These moths live on the energy collected during the period as caterpillar, the life expectancy of these moths is generally less than two weeks under optimal conditions. Lepidopterans that do take food, are equipped with a proboscis. This hollow tubular tongue is rolled up as a neat spiral when not used. The length of the proboscis varies from species to species and can by anything between a few tenth till 10 inch long like the tropical Sphinx Amphimoea walkeri. Generally nectar of flowers is sucked up with the proboscis but there are species that like rotting fruit and other liquids as well. On both sides of the proboscis, a labial palp is present, these are brush-like mouthparts that cover the proboscis almost completely if it is rolled up. Labial palps are used to check if the food is edible, they contain the taste buds of the lepidopteran.

The thorax

The thorax exists of three segments. Just like the segments of a caterpillar, each has one pair of segmented legs. The front legs of a butterfly are mostly much shorter than the pairs on the last two thorax segments, the front pair is used primarily for cleaning the antennae. At the end of each leg there are claws with which they are able to get hold on relatively smooth surfaces. The rear two segments of the thorax also contain the wings, the front wings on the second and the hind wings on the third segment. For the most part, the thorax is filled with muscles that are used to fly and crawl with.

The abdomen

The abdomen of the lepidopteran contains the digestive organs. The new created digestive tract has been build up again during pupa stage. The relatively large digestive tract of the caterpillar is unnecessary because the food consists almost exclusively of nectar. It’s much easier to subtract nutrients and energy from nectar so there is much less food to process and a heavy digestive tract wouldn’t help flying that much. The only thing a lepidopteran needs is energy to fly and moisture to prevent dehydration, after all it doesn’t grow anymore. Several species of butterflies still need some proteins and amino acids, this is especially important for some fragile longwing species from the Heliconiinae family that have a reasonably long lifespan. These butterflies usually can’t drag along their entire supply of eggs so they need the extra nutrients to develop ova during their lifetime. Those necessary nutrients and amino acids are obtained by dissolving and absorbing pollen.

The main task during the life of a lepidopteran is to produce offspring, the reproductive organs in the abdomen of the lepidopteran have also formed during pupa stage. In most cases, the female lepidopteran has a larger abdomen than the male, this is mainly because of all the eggs that the female bears with her. Due to the higher body weight, her wing area has to be larger as well, this has the consequence that a female lepidopteran of the same species is larger than a male. A male lepidopteran has a grabbing organ (claspers) at the end of his abdomen, that way he can get hold of the female during mating. The female has an ovipositor at the tip of her abdomen which she uses to lays eggs. For receiving sperm packages, the female has a receptacle that lays slightly more to the underside of her abdomen. Sperm is stored in her abdomen till it’s needed for fertilising the eggs, that is done while the egg moves through the ovipositor as she lays each egg.

Male moths in general, but particularly Saturniidae species that don’t feed, are attracted by the females pheromones, the female pheromone glands are placed at the base of her ovipositor. During calling time, usually in the early evening, you can see the glands and ovipositor bulging out and pheromones are spread. Male moths can scent these from miles away and will hurry to get there before another male does. These females will stay near the cocoon so the males won’t lose track and start flying after mating.