These darts are made in sexually mature animals only, and are used as part of the sequence of events during courtship, before actual mating takes place.

This is because mucus on the dart contains an allomone (pheromone-like) compound that promotes sperm preservation mechanisms in the female.

The two snails circle around each other for up to six hours, touching with their tentacles, and biting lips and the area of the genital pore, which shows some preliminary signs of the eversion of the penis.

As the snails approach mating, hydraulic pressure builds up in the blood sinus surrounding the organ housing the dart.

Recent research has led to a new understanding of the function of love darts: manipulating the recipient's snail's sperm collection mechanism, thus increasing the chances of paternity for the sender.

[10] A close look into the behavior of Cornu aspersum shows that this is achieved not by the mechanical action of the dart as it penetrates the recipient's skin, but by the mucus that coats the dart:[11] The mucus carries an allohormone that is transferred into the recipient's hemolymph when the dart is inserted,[12] which reconfigures the recipient's reproductive system: the bursa copulatrix (sperm digestion organ) becomes closed off, and the copulatory canal (leading to the sperm storage) is opened.

[11] The love dart, also known as a "gypsobelum", is often made of calcium carbonate[14] which is secreted by a specialized organ within the reproductive system of several families of air-breathing snails and slugs, mainly in terrestrial pulmonate gastropod mollusks within the clade Stylommatophora.

For example, individual snails of the two rather similar helicid species Cepaea hortensis and Cepaea nemoralis can sometimes only be distinguished by examining the shape of the love dart and the vaginal mucous glands (which in the anatomical diagram are marked "MG" and are positioned off the structure marked "V".)

The outer opening of the reproductive system is called the "genital pore"; it is positioned on the right hand side, very close to the head of the animal.

The exact positioning of the stylophore varies, but it is in the vicinity of the eversible penis and the vagina, where these two structures open into the "atrium", a common area right inside the genital pore.

The opening of the stylophore leads directly into the atrium in certain species in the families Vitrinidae, Parmacellidae, Helminthoglyptidae, Bradybaenidae, Urocyclidae, Ariophantidae, and Dyakiidae.

The opening of the stylophore can instead lead to the penis, as is the case in some species of Aneitinae (a subfamily of Athoracophoridae), Sagdidae, Euconulidae, Gastrodontidae and Onchidiidae.

[1] All pulmonate land snails are hermaphrodites, and have a complete and rather elaborate set of both male and female reproductive organs (see the simplified anatomical diagram above), but the majority of pulmonate land snails have no love darts and no dart sac.

Calcareous (composed of calcium carbonate) darts are found in a limited number of pulmonate families[1] within the Stylommatophora.

[17] Lightly calcified darts occur in the snail and semi-slug family Urocyclidae, within the superfamily Helicarionoidea.

Within the more ancient clade Systellommatophora, chitin darts are found in the pulmonate sea slugs of the family Onchidiidae, in the superfamily Onchidioidea.

Vestigial darts (ones that exist only in a rudimentary condition) occur in the family Sagdidae,[15] and in many Helicoidea, the surrounding organs have also degenerated (become non-functional).

The following tables or charts show numerous examples of love dart morphology, on a family-by-family and species-by-species basis.

Marine gastropods in the predatory superfamily Conoidea, (known as the toxoglossans, meaning "poison tongue") use a poison dart or harpoon, which is a single modified radula tooth which is created inside the mouth of the snail, and which is primarily made of chitin.

For example, in the Cephalaspidean genus Siphopteron, both seaslugs attempt to stab their partner with a two-part, spined penis.