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Glossary of Terms for Aquatic Macroinvertebrates


Abdomen - The area of the body behind the head and the thoracic segments.

Abdominal - Pertaining to structures on the abdomen.

Antenna (pl. antennae) - Sensory appendage on the head located between the eyes. They may be several times longer than the width of the head or extremely small and difficult to see even when magnified.

Anterior - At or directed toward the head or forward part of the body.

Apical - At the end or tip of a structure.

Aquatic - Living in or on water.

Chaetae - Hairlike bristles in worms. They can be very long, several times longer than the width of the body or just protruding from the body. These are mostly microscopic and difficult to see at less than a magnification of 100x.

Dorsal - Pertaining to the top or upper surface. The opposite of ventral.

Dorsal hump - A single wart-like structure found on the top of the first abdominal segment. It may be very prominent or appear as only a slight mound. Best seen in side view.

Exoskeleton - The hardened outside body wall of arthropods.

Gill - A structure that allows an orgasm to breath underwater. They are variable in length and form; from thread-like to plate-like.

Glossa - One of a pair of two lobes near the middle of an insects mouth.

Hind legs - The third pair of legs, the most posterior pair of legs.

Kick sample - A method of collecting aquatic macroinvertebrates from a wadable stream or river. A net or screen is held downstream at arms length and the substrate is disturbed by foot. Organisms are dislodged from the substrate and are carried by the current into the net.

Labium - The lower "lip" of the insect head.

Labrum - The upper "lip" of the insect head.

Larvae - The first life stage of insects; a developmental stage with many instars (the insect between molting) before becoming a winged adult.

Lateral humps - Paired wart-like structures that are found on the sides of the first abdominal segment. These may be very prominent or appear as only slight mounds. Best seen when looking at the larva from the top.

Macroinvertebrate - A small animal generally visible to the unaided eye, usually larger than 0.5 mm. These animals do not have a backbone.

Maxillary palp - One of a pair of segmented appendages located between the mandibles of insects.

Mesonotum - The middle sclerotized plate on the top of the thoracic segments.

Metamorphosis - The change of an animal from one form to another. e.g. the transformation of a larva to a pupa, or pupa to adult.

Mottled - Patterned with spots or blotches.

Nota - The dorsal surface of a body segment, especially of the thoracic segments.

Nymph - The immature or larval stage of some macroinvertebrates.

Omnivorous - Feeding on both animals and plants.

Paraglossa - One of a pair of two lobes near the middle of an insects mouth. These surround the glossa.

Posterior - At or toward the hind or tail end of the body.

Predaceous - Feeding or preying on other animals.

Proboscis - A tubular structure protruding from the head.

Process - An elongation of a surface, a margin or an appendage.

Proleg - A fleshy, unsegmented, leglike or lobelike structure. They can be single but often occur in pairs and can be located under the thorax, along the abdomen, or at the end of the abdomen. Proleg often bear terminal claws.

Pronotum - The top surface of the first, most anterior thoracic segment.

Prosternal - Underneath the first thoracic segment and between the first pair of legs.

Prosternal horn - A slender finger-like structure located just behind the underside of the head in some caddis larvae.

Setae -Hairlike structures that can be found on various parts of a macroinvertebrates body. They may be single, in rows, or in clusters.

Segment - A subdivision of the body.

Sclerotized - Hardened and usually darkened pertaining to the body wall.

Sternal - Pertaining to the ventral or underside of a body segment.

Subocular line - A line beneath or below the level of the eye.

Tarsal - The last segments of the leg. Often divided into two to five tarsal segments.

Terga - The upper or dorsal surface of any body segment.

Terrestrial - Living on land , instead of water.

Thoracic - Of the thorax. (The section of the body between the head and the abdomen)

Trochantin - A separate, small, platelike appendage of caddisfly larvae located anteriorly at the base of the foreleg.

Thorax - The part of the body between the head and the abdomen.

Ventral - Pertaining to the bottom or underside. The opposite of dorsal.

Wing pads - The encased undeveloped wings of nymphs

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