Nematus salicis (Willow sawfly) larvae on willow, Arnhem, the Netherlands

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 Sym ...

-shaped") is the

entomological Entomology () is the scientific study of insects, a branch of zoology. In the past the term "insect" was less specific, and historically the definition of entomology would also include the study of animals in other arthropod groups, such as arach ...

term describing a certain class of shapes of insect

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

Origin and application

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

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

"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 usually involving sexual intercourse or other forms of sexual penetration carried out against a person without their consent. The act may be carried out by physical force, coercion, abuse of authority, or ag ...

-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 30,000 species of beetles worldwide; they are often called scarabs or scarab beetles. The classification of this family has undergone significant change in recent years. Several sub ...

—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. T ...

— the weevils — are also called "

apodous Many vertebrates have evolved limbless, limb-reduced, or apodous forms. Reptiles have on a number of occasions evolved into limbless forms – snakes, amphisbaenia, and legless lizards (limb loss in lizards has evolved independently several tim ...

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 insects of the beetle family Chrysomelidae are commonly known as leaf beetles, and include over 37,000 (and probably at least 50,000) species in more than 2,500 genera, making up one of the largest and most commonly encountered of all beetle ...

, 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 Lepidoptera, though they can also be found on other larval insects such as sawflies and a few other types of 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 or chest is a part of the anatomy of humans, 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 divisions of the crea ...

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, are a large family of beetles, with over 35,000 species described. Most species are characterized by extremely long antennae, which are often as long as or longer than ...

(

Longhorn beetle The longhorn beetles (Cerambycidae), also known as long-horned or longicorns, are a large family of beetles, with over 35,000 species described. Most species are characterized by extremely long antennae, which are often as long as or longer than ...

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 ( ) is an order (biology), order of insects that includes butterfly, butterflies and moths (both are called lepidopterans). About 180,000 species of the Lepidoptera are described, in 126 Family (biology), families and 46 Taxonomic r ...

), caddis larvae (

Trichoptera The caddisflies, or 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 b ...

), and sawflies (

Symphyta Sawflies are the insects of 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 where they lay ...

)

References

External links

Bugguide.net
Insect morphology Larvae {{insect-stub