LEPIDOPTERA: CHARACTERISTICS, MIGRATIONS AND LIFE CYCLE - BIOLOGY - 2025

Lepidoptera (Lepidoptera) is a group of flying insects commonly known as butterflies, moths, or moths. These insects present a complete metamorphosis or holometabolism, where the egg, larva, pupal and imago phases occur.

It is one of the most numerous orders, with more than 150,000 species characterized by the striking colors of their wings. Its body and wings are covered by tiny scales whose function is to aerate the wing tracheae, mimic and refract sunlight.

Butterflies of the Papilionidae family (Papilio canadensis). Mdf, from Wikimedia Commons

Lepidopteran adults have the peculiarity of having two pairs of membranous wings covered by fine scales. The oral apparatus is formed by the maxillae and a flexible blowhole that allows it to feed on the nectar of the flowers.

Generally, the globular eggs with an ornate surface are placed on the upper side or underside of the leaves. The larvae have a cylindrical body, with false legs or protopaths and a well-developed head with a chewing mouthpiece.

The pupae or chrysalis is an immobile state, in this phase they do not feed and undergo a metamorphosis before being released. The adult emerges breaking the cover of the chrysalis, being short-lived, the time necessary to perpetuate the species.

At the agricultural level, Lepidoptera influence the production chain, since different species are crop pests in their larval stage. In fact, the larvae can feed in various ways, defoliating or undermining the roots, stems, leaves and fruits of various crops.

General characteristics

Lepidopterans are characterized by a well-developed globose head, with a pair of compound eyes and numerous ommatidia. Some species have two ocelli, located between or on the compound eyes.

They have a pair of antennas located between the compound eyes, of different sizes and structures, with a large number of devices. Each species is characterized by the type of antenna, being filiform, feathery, pectinate, bipectinate, nailed or capitate.

The oral apparatus is of the sucking-licking type, with an extendable proboscis or trunk and an internal spirit tube that facilitates feeding. On each side there are two sensitive structures called labial palps whose function is to examine food.

The three segments of the thorax are covered by tiny fibrils or hairs, the prothorax being the smallest. The mesothorax has a greater development and size, and is the place where the auditory organs are located.

The abdomen has a cylindrical or conical shape, formed by several uromers and the reproductive system is located at the posterior end. Females have an ovipositor with a group of hairs that excrete sexual pheromones that guarantee mating between species.

Like all insects, they have six pairs of legs inserted in each segment of the thorax. They have five segments, spurs or epiphysis and a pair of nails; some have stunted first pair of legs.

They have a pair of membranous wings covered by tiny scales (250-700 microns), attached to the second and third thoracic segments. The wings have characteristic coloration according to the species, highly resistant and flexible to be able to fly.

The coloring of the wings is determined by the way the scales fit across their surface. The colors range from light and bright to opaque and dark, and their function is camouflage, defense or courtship.

Taxonomy

The order Lepidoptera belongs to the kingdom Animalia, phylum Arthropoda, subphylum Hexápoda, class Insecta, infraclass Neoptera and superorder Endopterygota. Lepidoptera constitute more than 120 families, however, new families and species are continually excluded, incorporated or renamed.

The classification based on agricultural importance is one of the most applied. In this regard, the order Lepidoptera includes two suborders: Homoneura, with the same veins, and Heteroneura, with different veins.

In the Homoneura the distribution and size of the veins is the same in both pairs of wings. They are primitive species, with a simple chewing-type mouthpart, wings inserted through lobes, and without agricultural importance.

Differential venation is characteristic of the Heteroneura in terms of size and shape, the first pair of wings being larger than the second. The nocturnal butterflies with crepuscular habits (Heterocera Division) and the diurnal ones (Ropalocera Division) belong to this suborder.

The main families of Lepidoptera of agricultural importance include: Crambidae, Cecidosidae, Cossidae, Erebidae, Gelechidae, Geometridae, Hesperiidae, Noctuidae, Nymphalidae, Papilionidae, Pieridae, Plutellidae, Pterophoridae, Pyralidae, Saturniidae, Sesraniidae, Sphingidae, Tortricidae.

Habitat and food

Species of the order Lepidoptera are found in almost all habitats on the planet, from coastal areas to mountainous areas, including urban areas. Its survival is determined by abiotic factors such as altitude, latitude and climate, mainly temperature and humidity.

Their behavior is highly variable, finding species with migratory habits that travel great distances in search of food or reproduction. However, there are sedentary species, which limit their life cycle to a reduced space or specific crop, such as agricultural pests.

Lepidoptera feed by sucking the nectar and honey from the flowers, through the spirit of the oral apparatus. Only the species of the family Micropterigidae have a chewing mouth apparatus, feeding on pollen or plant structures.

As for the larvae or caterpillars, they consume all the plant material available: roots, stems, leaves, flowers and fruits. Some species are miners, forming tunnels on the surface of the leaves, and other species feed on stored flour or grains.

Some species, mainly nocturnal, never feed, obtaining their energy from the reserves stored in their larval stage. In seasonal areas, certain species go dormant in winter, limiting their feeding and taking advantage of the reserves collected as caterpillars.

Migrations

Lepidopterans, despite their fragility and size, have the ability to undertake migrations to ensure their survival and feeding. Climate change is one of the causes of migration, in some cases it is the need to establish new colonies.

Monarch Butterfly (Danaus archippus). Source: flickr.com

Some families of Licénidos, Nyfalidos and Pierídos, migrate inside their original biotope, others outside the biotope without ever returning. Families such as the Daniados migrate out of their original biotope, the next generation returning to the site of origin.

In America the monarch butterfly, Danaus plexippus, is famous, which migrates every year from the Caribbean to the United States and Canada. In Europe, the species Cynthia cardui travels from North Africa, through the Strait of Gibraltar to the north.

Their migratory capacity is surprising. When the weather conditions are favorable, colonies of Danaus plexippus have been established in the Canary Islands. In both cases, each species after feeding and procreating, returns to its place of origin.

Lifecycle

The order Lepidoptera is characterized by a very versatile life cycle, determined by its taxonomy and environmental conditions. Factors such as temperature, humidity and season determine the life span of each individual, which ranges from a few days to months.

Indeed, these insects present a complete metamorphosis (holometabolism) where all the phases are completely different. Larvae differ from adults in their anatomy and eating habits, being preceded by an immobile or pupal stage.

Sexual dimorphism

Several species exhibit a marked sexual dimorphism, since the males have a different morphology than the females. In fact, this differentiation in size, coloration and appearance of the wings tends to confuse each sex as separate species.

The dimorphism is mainly reflected in the obverse of the wings, likewise, the females are larger than the males. Geographic isolation is another factor that generates intraspecific differentiations, originating in many cases new subspecies.

An example of polymorphism occurs in some species of Licénidos, where variations of coloration in the wings are observed. Generally the upper part of the wings is blue in the male and brown in the female.

Reproduction

The reproduction of the Lepidoptera is sexual, being regularly oviparous. As holometabolic insects they go through the stages of egg, larva (caterpillar), pupa (chrysalis) and adult (imago).

Eggs

The eggs are the first reproductive phase of the Lepidoptera, being in charge of protecting the development of the embryo before hatching. The eggs are deposited in the soil and on the surface or under the leaves of various plant species.

Lepidoptera eggs. Source: flickr.com

The appearance and color of the eggs is characteristic of each species, with a size of 0.2 to 6 mm. The duration of the embryonic phase depends on the environmental conditions being favorable for the larva to hatch.

When the eggs have matured to hatch, they tend to be transparent, with the larva inside being perceptible. Once the larva has hatched from the egg, with its chewing mouth apparatus it begins its development, consuming the remains of the shell.

Larva (caterpillar)

The larvae at the time of hatching are as small as the eggs, as they feed they grow exponentially. Initially they feed on the debris of the egg and later on the leaves, stems, flowers and fruits of the host plants.

Lepidoptera caterpillars (Cucullia scrophulariae) Source: flickr.com

The objective of the larva is to feed, grow and store energy necessary for the next phase of development. During this phase the larva replaces or sheds the skin that protects it several times due to the continuous increase in size.

The physiognomy of the larvae is determined by genus and species, presenting a diversity of sizes, colors, textures and anatomical characters. Generally, a caterpillar has a head, thorax, and abdomen.

The differentiated head has two simple eyes, antennae and a chewing mouth apparatus, being very active in devouring all surrounding plant material. Because they lack compound eyes, they have limited vision and are slow moving.

In fact, the eggs are deposited in the host plant, so they fulfill this stage in one place. The larval phase does not last long, hence its voracity to obtain the greatest amount of food quickly.

Pupa (chrysalis)

This phase is the most important of the development of the Lepidoptera, in it the true metamorphosis occurs. In this regard, it begins when the fully developed larva or caterpillar becomes immobilized and stops consuming food.

Chrysalis of Lepidoptera. Source: pixabay.com

To do this, once enough energy, fat and protein have been accumulated, it chooses a sheltered place to start the pupal phase. According to the type of species and environmental conditions, this stage differs in terms of development and effective time.

Once the appropriate site is selected, the caterpillars hang upside down through silk threads, form cocoons between the leaves or by weaving nets. The cocoon of the chrysalis has the function of protecting the butterfly while the morphological changes that will form the adult take place.

New tissues and organs develop within the chrysalis, as well as legs, antennae, and wings. This stage has a variable duration, it can last weeks or months, depending on the species and environmental conditions.

Adult (imago)

After the transformation of the larva within the chrysalis, the adult butterfly emerges from the cocoon. When leaving, the wings appear rough and weak, but after a few minutes they irrigate and harden, achieving their final size.

Lepidoptera adult. Source: flickr.com

The adult of the butterfly has the function of reproducing and preserving the species, initiating a selection process to find a mate. Each genus and species determines the duration of the adult phase, lasting from a few days to several months.

The courtship of males and females is determined by their particular flapping and by activating the sense of smell. After fertilization, the female lays hundreds of eggs, initiating a new life cycle.

Importance

From an ecological point of view, lepidoptera represent a high percentage of the biodiversity of the ecosystems where they inhabit. In addition to their pollinating activity, other living beings can behave as predators or be part of the trophic chain.

The presence of a certain species of lepidoptera is a bioindicator of the existence of animal and plant species or particular environmental conditions. In effect, they act as crop pests, are a source of food and are prey to natural enemies.

Butterflies are susceptible to drastic changes in temperature, humidity, wind and luminosity, being indicators of the anthropic transformations of ecosystems. Furthermore, thanks to the close lepidopteran-plant interrelation, their biodiversity allows us to check the plant diversity on a given surface.

At the agricultural level, some species of Lepidoptera are pests in their larval stage, and others can be used for comprehensive biological control. The reproduction of the species Bombyx mori (Bombycidae) whose larvae weave silk cocoons, have been used to make silk fabrics.

References

1. Coronado Ricardo and Márquez Antonio (1986) Introduction to Entomology: Morphology and Taxonomy of Insects. Editorial Limusa. ISBN 968-18-0066-4.
2. Culin Joseph (2018) Lepidopteran. Recovered at: britannica.com
3. García-Barros, E., Romo, H., i Monteys, VS, Munguira, ML, Baixeras, J., Moreno, AV, & García, JLY (2015) Orden Lepidoptera. Magazine - SEA, nº 65: 1–21. ISSN 2386-7183.
4. Fraija Fernandez, N., & Fajardo Medina, GE (2006). Characterization of the fauna of the order Lepidoptera (Rhopalocera) in five different localities of the eastern Colombian plains. Acta Biológica Colombiana, 11 (1).
5. Urretabizkaya, N., Vasicek, A., & Saini, E. (2010). Harmful Insects of Agronomic Importance I. Lepidoptera. Buenos Aires, Argentina: National Institute of Agricultural Technology.
6. Zumbado, MA and Azofeifa, D. (2018) Insects of Agricultural Importance. Basic Guide to Entomology. Heredia, Costa Rica. National Program for Organic Agriculture (PNAO). 204 pp.