Eruciform (literally: "

caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder ...

-shaped") is the

entomological Entomology (from Ancient Greek ἔντομον (''éntomon''), meaning "insect", and -logy from λόγος (''lógos''), meaning "study") is the branch of zoology Zoology ( , ) is the scientific study of animals. Its studies include the ...

term describing a certain class of shapes of insect

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

Origin and application

The word ''eruciform'' literally means "caterpillar-shaped" (from

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

"eruca", a caterpillar — confusingly, in Latin "

Eruca ''Eruca'' is a genus of flowering plants in the family Brassicaceae, native to the Mediterranean region, which includes the leaf vegetable known as arugula or rocket. The number of species is disputed, with some authorities only accepting a sin ...

" also was used as the name for a

rape Rape is a type of sexual assault involving sexual intercourse, or other forms of sexual penetration, carried out against a person without consent. The act may be carried out by physical force, coercion, abuse of authority, or against a person ...

-like plant, but that has no clear connection to the current context). The term encompasses many variations in shape. Some larvae, for example, are in fact shaped like certain other, straight, eruciform larvae, except that they are curved into a C-shape. These are called "scarabaeiform" because it is the typical form of the larvae of the

Scarabaeidae The family Scarabaeidae, as currently defined, consists of over 35,000 species of beetles worldwide; they are often called scarabs or scarab beetles. The classification of this family has undergone significant change. Several groups formerly tre ...

—the scarab beetles and their relatives. In contrast, larvae of the

Curculionidae The Curculionidae are a family of weevils, commonly called snout beetles or true weevils. They are one of the largest animal families with 6,800 genera and 83,000 species described worldwide. They are the sister group to the family Brentidae. Th ...

— the weevils — are also called "

apodous Many vertebrates are limbless, limb-reduced, or apodous, with a body plan consisting of a head and vertebral column, but no adjoining limbs such as legs or fins. Jawless fish are limbless but may have preceded the evolution of vertebrate limbs, w ...

eruciform", (literally meaning legless caterpillar-shaped; unlike scarab larvae, they do not have legs). This seems rather inconsistent, because commonly weevil larvae are almost as C-shaped as scarab larvae.

Variations and implications

Some larvae, such as those of most beetles in the family

Chrysomelidae The beetle family Chrysomelidae, commonly known as leaf beetles, includes over 37,000 (and probably at least 50,000) species in more than 2,500 genera, making it one of the largest and most commonly encountered of all beetle families. Numerous s ...

, are described as eruciform, although they are short, have swollen abdomens, and have no true "

proleg A proleg is a small, fleshy, stub structure found on the ventral surface of the abdomen of most larval forms of insects of the Order (biology), order Lepidoptera, though they can also be found on larvae of insects such as symphyta, sawflies. In ...

s" such as caterpillars have. Typically they walk freely on leaves and similar surfaces, using the "true" six legs on the three

thoracic The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main ...

segments just behind the head. The abdomen is carried behind as a more or less swollen, hump-backed rear end. In contrast, larvae of the

Cerambycidae The longhorn beetles (Cerambycidae), also known as long-horned or longicorns (whose larvae are often referred to as roundheaded borers), are a large family of beetles, with over 35,000 species described. Most species are characterized by anten ...

(

Longhorn beetle The longhorn beetles (Cerambycidae), also known as long-horned or longicorns (whose larvae are often referred to as roundheaded borers), are a large family of beetles, with over 35,000 species described. Most species are characterized by Antenn ...

s) are generally straight and could fairly be described as "apodous eruciform". They live in tunnels, typically in wood, where a distended abdomen would be a liability and legs are not the only option for locomotion. Instead of using legs Cerambycid larvae press fleshy bulges against the walls of their tunnels. Arguably the most typically eruciform larvae, prolegs and all, are to be found among the butterflies and moths (

Lepidoptera Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...

), caddis larvae (

Trichoptera The caddisflies (order Trichoptera) are a group of insects with aquatic larvae and terrestrial adults. There are approximately 14,500 described species, most of which can be divided into the suborders Integripalpia and Annulipalpia on the basis ...

), and sawflies (

Symphyta Sawflies are wasp-like insects that are in the suborder Symphyta within the order Hymenoptera, alongside ants, bees, and wasps. The common name comes from the saw-like appearance of the ovipositor, which the females use to cut into the plants ...

)

References

External links

Bugguide.net
Insect morphology Larvae {{insect-stub