Heliciculture/Mating and Egg Laying
Snails are hermaphrodites. Although they have both male and female reproductive organs, they must mate with another snail of the same species before they lay eggs. Some snails may act as males one season and as females the next. Other snails play both roles at once and fertilize each other simultaneously. When the snail is large enough and mature enough, which may take several years, mating occurs in the late spring or early summer after several hours of courtship. Sometimes there is a second mating in summer. (In tropical climates, mating may occur several times a year. In some climates, snails mate around October and may mate a second time 2 weeks later.) After mating, the snail can store sperm received for up to a year, but it usually lays eggs within a few weeks. Snails are sometimes uninterested in mating with another snail of the same species that originated from a considerable distance away. For example, a H. aspersa from southern France may reject a H. aspersa from northern France.
Snails need soil at least 2 inches deep in which to lay their eggs. For H. pomatia, the soil should be at least 3 inches deep. Keep out pests such as ants, earwigs, millipedes, etc. Dry soil is not suitable for the preparation of a nest, nor is soil that is too heavy. In clay soil that becomes hard, reproduction rates may decrease because the snails are unable to bury their eggs and the hatchlings have difficulty emerging from the nest. Hatchability of eggs depends on soil temperature, soil humidity, soil composition, etc. Soil consisting of 20% to 40% organic material is good. Keep the soil 65 F to 80 F, best around 70. Maintain soil moisture of 80%. One researcher removes eggs immediately after they are deposited, counts them, then keeps them on moist cotton until the eggs hatch and the young start to eat. Snails lose substantial weight by laying eggs. Some do not recover. About one-third of the snails will die after the breeding season.
H. pomatia eggs measure about 3 mm in diameter and have a calcareous shell and a high yolk content. H. pomatia lays the eggs in July or August, 2 to 8 weeks after mating, in holes dug out in the ground. (Data varies widely on how long after mating snails lay eggs.) The snail puts its head into the hole or may crawl in until only the top of the shell is visible; then it deposits eggs from the genital opening just behind the head. It takes the snail 1 to 2 days to lay 30 to 50 eggs. Occasionally, the snail will lay about a dozen more a few weeks later. The snail covers the hole with a mixture of the slime it excretes and dirt. This slime, which the snail excretes to help it crawl and to help preserve the moisture in its soft body, is glycoprotein similar to eggwhite.
Fully-developed baby H. pomatia snails hatch about 3 to 4 weeks after the eggs are laid, depending on temperature and humidity. Birds, insects, mice, toads and other predators take a heavy toll on the young snails. The snails eat and grow until the weather turns cold. They then dig a deep hole, sometimes as deep as 1 foot, and seal themselves inside their shell and hibernate for the winter. This is a response to both decreasing temperature and shorter hours of daylight. When the ground warms up in spring, the snail emerges and goes on a binge of replacing lost moisture and eating.
H. aspersa eggs are white, spherical, about 3 mm in diameter and are laid 5 days to 3 weeks after mating. (Data varies widely due to differences in climate and regional variations in the snails' habitats.) H. aspersa lays an average of 85 eggs in a nest that is 1- to 1 1/2-inches deep. Data varies from 30 to over 120 eggs, but high figures may be from when more than one snail lays eggs in the same nest.
In warm, damp climates, H. aspersa may lay eggs as often as once a month from February through October, depending on the weather and region. Mating and egg-laying begin when there are at least 8 hours of daylight and continue until days begin to get shorter. In the United States, longer hours of sunlight that occur when temperatures are still too cold will affect this schedule, but increasing hours of daylight still stimulate egg laying. If warm enough, the eggs hatch in about 2 weeks, or in 4 weeks if cooler. It takes the baby snails several more days to break out of the sealed nest and climb to the surface. In a climate similar to southern California's, H. aspersa matures in about 2 years. In central Italy, H. aspersa hatches and emerges from the soil almost exclusively in the autumn. If well fed and not overcrowded, those snails that hatch at the start of the season will reach adult size and form a lip at the edge of their shell by the following June. If you manipulate the environment to get more early hatchlings, the size and number of snails that mature the following year will increase. In South Africa, some H. aspersa mature in 10 months, and under ideal conditions in a laboratory, some have matured in 6 to 8 months. Most of H. aspersa's reproductive activity takes place in the second year of its life.
By contrast, one giant African snail, Achatina fulica, lays 100 to 400 elliptical eggs that each measure about 5 mm long. Each snail may lay several batches of eggs each year, usually in the wet season. They may lay eggs in holes in the ground like H. pomatia, or lay eggs on the surface of a rocky soil, in organic matter, or at the base of plants. In 10 to 30 days, the eggs hatch releasing snails about 4 mm long. These snails grow up to 10mm per month. After 6 months, the Achatina fulica is about 35mm long and may already be sexually mature. Sexual maturity takes 6 to 16 months, depending on weather and the availability of calcium. This snail lives 5 or 6 years, sometimes as many as 9 years.