see text Helix is a genus of large, air-breathing land snails native to the western Palaearctic and characterized by a globular shell.

[1][2] It is the type genus of the family Helicidae, and one of the animal genera described by Carl Linnaeus[3] at the dawn of the zoological nomenclature.

[7] In Linnaeus' 10th edition of Systema Naturae, which marks the beginning of the zoological nomenclature, the generic name Helix had been used for a variety of terrestrial (e.g. Zonites algirus), freshwater (e.g. Lymnaea stagnalis), and marine (e.g. Fossarus ambiguus) gastropods.

Later authors restricted the name's use to stylommatophoran species with flattened to globular shells, including zonitids and other groups.

Two subgenera are currently recognized:[2][15] Helix comprises large land snails species, with shell diameter of 2–6 cm.

There appears to be a tendency for a shortening of the diverticulum of bursa copulatrix and of the eppiphallus, but there is an overlap with related genera in these characters.

The southernmost species live in North Africa (H. melanostoma, H. pronuba) and the southern Levant (H. engaddensis).

The albumen gland provides nourishment for the developing fertilized eggs, and its size greatly varies with the stage of the reproductive cycle.

[32] The male genitalia consist of a tube that serves the formation of a spermatophore and its transfer into the female parts of the mating partner.

The stalk in most cases bears a diverticulum, a blind tube that receives the front part of the spermatophore if present.

The diverticulum has been proposed to be a remnant of a seminal duct that originally transported foreign sperm into the fertilization pouch.

The single dart is aragonitic, straight or only weakly curved, with four blades (vanes) along its length and a corona at its base.

During the development, folds form along the internal space of the tube than eventually completely separte first vas deferens and penis, then also bursa copulatrix.

[36] The male and female parts open into a common atrium and a genital pore positioned ventrally behind the right optic tentacle.

A rare teratological individual with paired male genitalia (penis, epiphallus, flagellum) has been reported from Germany.

The mucous glands produce a whitish secretion just before the shooting, that contains hormones promoting the compound that improves preservation of foreign sperm in the receiving individual.

[39] Then, again after a pause, comes the copulation, usually preceded by several unsuccessful attempts in which the reciprocal insertion of penes is not achieved and the genital organs are partially retracted back into the body.

[47][48] In H. pomatia, sexual maturity is reached after 2–4 (–6) overwinterings, i.e. at the age of 2–4 (–6) years, but this differs between localities as well as between snails from the same clutch.

[49][50] The age of H. pomatia individuals can be estimated by counting growth interruptions on the shell and the number of layers deposited on the aperture margin lip.

The time from hatching to first egg laying can be shortened in H. pomatia to just 12–13 months under optimal conditions in the captivity, mainly by skipping hibernation.

Some species are exclusively found in open limestone rocky habitats (H. secernenda), while others tolerate acidic bedrock (e.g. H. pelagonesica) or live predominantly in forests (e.g. H. thessalica).

[58] Active dispersal during the lifetime may lead to displacement by more than 200 m.[59] Several species (e.g. H. pomatia, H. salomonica) build a thick, calcified epiphragm that closes the shell's aperture during hibernation or aestivation.

This has been observed in Phasianus colchicus, Burhinus oedicemus, Coracias garrulus, Lanius excubitor, corvids, and probably other birds.

[49] Larvae of flies from several families attack Helix snails and may kill even adults (Phoridae, Muscidae, Sarcophagidae, Sciomyzidae).

Mesolithic shell midden dated to 9370 ± 80 and 8110 ± 90 uncalibrated C-14 years bp and providing evidence of collecting was documented for H. pomatella in Abruzzo, Italy.

[75] Helix salomonica was consumed in the Zagros in large amount during the Pre-Pottery Neolithic, with evidence of consumption from ~12,000 BC.

[78] Ancient Romans collected snails for food and even held them in enclosures, as described by Marcus Terentius Varro (in De Re Rustica, and repeated by Pliny the Elder).

[80] One of the species, H. ceratina, is critically endangered and the present known distribution is limited to a very small area near the Ajaccio airport.

[81][52] In the past, collection of wild H. pomatia for food led to fears of over-exploitation and the introduction of protection by law in several countries.

The most studied species in this respect is H. pomatia, where the fossils have been used to document the earliest postglacial occurrences in Central Europe.