Eruciform
Encyclopedia
Eruciform is the entomological
term describing a certain class of shapes of insect larva
e.
"eruca", a caterpillar — confusingly, in Latin "Eruca
" also was used as the name for a rape-like plant, but that has no clear connection to the current context).
One should not take the "caterpillar-shaped" description too seriously; there are many shapes of caterpillars besides the typical silkworm larva, and insect larvae of many shapes, not obviously caterpillar-like, are described as eruciform. Some 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 scarab beetles and their relatives. In contrast, larvae of the "Curculionidae
" — the weevils — are also called "apodous 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.
s" such as caterpillars have. Typically they walk freely on leaves and similar surfaces, using the "true" six legs on the three thoracic
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 (Longhorn beetle
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
), caddis larvae (Trichoptera
), and sawflies (Symphyta)
Entomology
Entomology is the scientific study of insects, a branch of arthropodology...
term describing a certain class of shapes of insect larva
Larva
A larva 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...
e.
Origin and application
The word "eruciform" literally means "caterpillar-shaped" (from LatinLatin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
"eruca", a caterpillar — confusingly, in Latin "Eruca
Eruca
Eruca is a genus of flowering plants in the family Brassicaceae, native to the Mediterranean region.The number of species is disputed, with some authorities only accepting a single species, while others accept up to five species. The following species are accepted by the Med-Checklist:*Eruca...
" also was used as the name for a rape-like plant, but that has no clear connection to the current context).
One should not take the "caterpillar-shaped" description too seriously; there are many shapes of caterpillars besides the typical silkworm larva, and insect larvae of many shapes, not obviously caterpillar-like, are described as eruciform. Some 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
Scarabaeidae
The family Scarabaeidae as currently defined consists of over 30,000 species of beetles worldwide. The species in this large family are often called scarabs or scarab beetles. The classification of this family is fairly unstable, with numerous competing theories, and new proposals appearing quite...
" -- the scarab beetles and their relatives. In contrast, larvae of the "Curculionidae
Curculionidae
Curculionidae is the family of the "true" weevils . It was formerly recognized in 1998 as the largest of any animal family, with over 40,000 species described worldwide at that time...
" — the weevils — are also called "apodous 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, are described as eruciform, although they are short, have swollen abdomens, and have no true "prolegProleg
A Proleg is the 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 types of flies....
s" such as caterpillars have. Typically they walk freely on leaves and similar surfaces, using the "true" six legs on the three thoracic
Thorax (insect anatomy)
The thorax is the mid section of the insect body. It holds the head, legs, wings and abdomen. It is also called mesosoma in other arthropods....
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 (Longhorn beetle
Longhorn beetle
The longhorn beetles are a cosmopolitan family of beetles, typically characterized by extremely long antennae, which are often as long as or longer than the beetle's body...
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
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
), caddis larvae (Trichoptera
Trichoptera
The caddisflies are an order, Trichoptera, of insects with approximately 12,000 described species. Also called sedge-flies or rail-flies, they are small moth-like insects having two pairs of hairy membranous wings...
), and sawflies (Symphyta)