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Anatomical Terms for Lepidoptera
Abdomen: The most posterior of the three major portions of an insect’s body (the others: head and thorax). Abdomen contains a portion of the digestive tract, osmoregulatory apparatus, and reproductive structures.
Aedeagus: The male organ for delivering sperm during copulation—functionally acting as a penis.
Anal angle: The point of a wing that is between the outer margin and the inner margin; where the outer and inner margins converge.
Androconial organs: Regions on the adult male body that release pheromones used in courtship activities. These regions sometimes consist of modified wing scales in distinct patches (androconial patches). In some moths, the organ consists of inflatable tubes at the tip of the abdomen.
Antenna: One of a pair of modified head appendages serving to sense the environment. Antennae are especially important for adult Lepidoptera that must recognize pheromones emitted from potential mates—specialized regions are exquisitely sensitive to molecules of pheromone contacting them. Adult antennal shape is one of the identification clues used by taxonomists.
Apex: The point of a wing that is between the costal margin and the outer margin; where the costal and outer margins converge.
Appendages: Extensions of an insect’s body, usually occurring in pairs. Although the legs and wings are the most conspicuous appendages, several other body parts can also be considered as modified appendages: antennae, mouth parts, genitalic apparatus, etc.
Bursa copulatrix: The sac in the female reproductive tract into which a spermatophore is deposited during copulation.
Cell: A portion of each wing that is relatively devoid of veins, although entirely surrounded by veins. The large cell located from the wing’s base to near the center of the wing is called the discal cell.
Compound eyes: The prominent areas on the left and right sides of the adult head, used for vision. Each such area is composed of hundreds of lens systems, individually providing the nervous system with information about the light hitting it.
Costa: The most anterior (leading) edge of a wing. Also called costal margin.
Coxa: The portion of an adult leg that is closest to the body.
Cremaster: A group of tiny hooked setae at the abdominal tip of some pupae. They serve to provide attachment to the inside of a cocoon or to some surface.
Crochets: hook-like devices at the tips of a caterpillar’s prolegs, enabling the animal to adhere tightly to a substrate such as a leaf. The pattern of crochets on a proleg is sometimes used as a clue in identifying caterpillars.
Cuticle: The outermost surface of an insect. It is composed mostly of a complex mix of proteins and polysaccharides.
Dash: A narrow, short line of dark pigmentation on a wing of some moth species. It is aligned on an axis from the base of the wing toward the terminal edge.
Discal cell: See cell.
Exoskeleton: A skeleton is the rigid structure to which muscles are attached. An exoskeleton is formed on the outside of an animal, rather internally. The exoskeleton of insects is identical to their cuticle. All insects, indeed all Arthropods, possess an exoskeleton.
Femur: The portion of an adult leg that is between the coxa and the tibia. It is distal to the coxa.
Forewings: The most anterior pair of wings.
Frenulum: One or more short spines projecting anteriorly from each hindwing of a moth, at the wing’s base. The frenulum acts like a hook, attaching to a small structure on the under-surface of the forewing. This “velcro” pair of structures acts to hold both wings together, producing a more coordinated flight structure. Most moth species this feature; nearly all butterflies lack it.
Genitalia: The reproductive structures, both internally and externally.
Haustellum: See proboscis.
Head:
The most anterior of the three major portions of an insect’s body (the
others: thorax and abdomen). The
head contains mouthparts, sensory
apparatus, and a rudimentary brain-like structure.
Hindwings: The most posterior pair of wings.
Inner margin: The most posterior (trailing) edge of a wing.
Lashes: Groups of bristles found near the compound eyes of some moths. The presence and location of lashes are identification clues for moth species.
Leg segments: The parts of the adult legs. See on this page: coxa, femur, tibia, tarsus.
Mandibles: A larva has a pair of tough, sharp-edged mandibles to the left and right of its mouth, used for chewing food. Very few species have mandibles as adults, since most species rely on uptake of liquid food via the proboscis.
Ocellus:
A single eye lens and associated nerve on the head of either a larva
or an adult. In adults, an ocellus is typically located dorsally
from (above) the base of each antenna. In larvae, the head surface typically
has two clusters of six ocelli, each cluster forming a crescent shape. Ocelli
probably sense only light and dark, rather than shapes. A synonym for ocelli:
stemmata.
Outer margin: The edge of a
wing that is farthest from the body; between the inner
margin and the costal margin.
Proboscis: A tubular structure of adult butterflies or moths, used for feeding. The proboscis is usually coiled near the ventral surface of the head when feeding is not occurring. It is composed of two hollow appendages fused together. All butterflies and nearly all moths have a functional proboscis. A synonym for proboscis: haustellum.
Prolegs: Fleshy leg-like objects located on several abdominal segments of a caterpillar. Most lepidopterans have five pairs, but some moths have only two pairs. Each proleg has a set of crochets used to adhere to the substrate.
Scales: The defining anatomical structures of Order Lepidoptera. Scales are tiny modified bristles covering most of the body surface. Most scales of the wings are flattened and overlapping, resembling in miniature the shingles on the roof of a house. Scales contain the molecules (pigments) that provide much of the color of the lepidopteran wings. Some wing colors are produced by the interplay of light with microscopic structures of scales, rather than involving pigments. See the FAQ #5 for discussion of the function of color.
Segment: All insects show marks along their body surface that indicate the margins of segments. Each segment has its own characteristic shape and many segments have protruding appendages of various sizes, shapes, and functions. Insect legs and antennae are also segmented.
Setae: Bristle-like extensions from the cuticle of either a larva or an adult. Setae of wings are modified to become the scales.
Spermatophores: Bundles containing sperm cells deposited into the female reproductive tract during copulation. A spermatophore, whose structure is made mostly of protein, typically encases several thousand sperm cells. The non-sperm components of a spermatophore are absorbed by the female and become significant nutritional material for her as she produces eggs.
Spine: A non-movable extension of the cuticle of an adult’s leg. The presence, size, and location of spines are identification clues for some species.
Spinnerets: A set of larval structures in the head region that extrude silk from underlying silk-producing glands.
Spiracles: Tiny openings along the sides of either a larva or an adult, leading to a complex system of tubes (tracheae) within the body. The spiracles and tracheae carry air to body tissues, for gas exchange.
Spur: An extension of the cuticle of an adult’s leg, anchored in a socket so that it is movable. The presence, size, and location of spurs are identification clues for some species.
Stemmata: See ocellus.
Tarsus: The segment of an adult leg that is farthest from the body. It is distal to the tibia.
Tegula: A small leaf-like appendage of a thoracic segment of an adult lepidopteran. It extends posteriorly, slightly overlapping the base of a forewing. It may function to protect the base of the wing. Tegulae are covered with scales, so they can be of various colors.
Thoracic legs: Three pairs of segmented legs of a caterpillar, more anterior than the pairs of unsegmented prolegs. These appendages are part of the first three segments (thoracic segments: T1, T2, T3) just posterior to the head.
Thorax: The middle portion of an insect’s body (the others: head and abdomen). The thorax contains a portion of the digestive tract, and a rudimentary heart-like tube. It is the point of attachment for legs and wings.
Tibia: The portion of an adult leg that is between the femur and the tarsus. It is distal to the femur.
Tympanum: One of a pair of somewhat circular membranes on the surface of the thorax or abdomen of many adult Lepidoptera. It functions much like a human’s ear drum, vibrating when sound waves strike it and converting this motion into nerve transmissions for analysis by the nervous system.
Veins: The fluid-filled tubes that radiate out into adult lepidopteran wings from the body. Veins perform several functions. Just after eclosion from the pupal cuticle, the animal’s veins are pumped full of a blood-like liquid, hemolymph. This forceful action causes expansion of the wings into their adult shape. Since the walls of veins are made of cuticle, they harden to provide support for the otherwise fragile wings throughout adult life. The hemolymph within veins also acts as a delivery system for nutrients and oxygen from the rest of the body (although there is nothing analogous to our blood circulation pattern). Veins also provide important clues to taxonomists—their pattern is a diagnostic tool in determining the family-level identification of a moth or butterfly.
Valva: One of two side-by-side flap-like structures of a male, used to clasp a female’s abdomen during copulation.
Venation: The pattern of wing veins. Used by taxonomists to help determine the family-level identification of a moth or butterfly.
Wing portions:
See on this page: inner margin, outer
margin, costa, cell.