Facebook YouTube Instagram Nederlands English

A review of the land mollusks of the Belgian Congo
Agaatslakken (Achatina)

In the period from 1909-1915 The American Museum of Natural History in Philadelphia had some expeditions to what was then the Belgian Congo (now Democratic Republic of Congo). These expeditions were largely conducted in two districts: Lower Congo, from Leopoldsville (Kinshasa) and Thysville (Mbanza-Ngungu) to Banana at the estuary and in the Aruwimi-Ituri valley. Occasional investigations were also conducted in Stanleyville (Kisangani) and northeast of the rainforest in Faradje.

Henry A. Pilsbry (Iowa City, December 7, 1862 - Lantana, Florida, October 26, 1957) investigated more than 6,000 land snails from the Belgian Congo, 4,200 of which were collected during the aforementioned expeditions. The others came from other expeditions such as that of J. Bequart near the Semliki River, on Mt. Ruwenzori (now the Rwenzori Mountains), south of Rutshuru and in Lower Congo.

The result of the research was cast in a book: 'A review of the land mollusks of the Belgian Congo'. From the approximately 400 species described, we only consider the Achatina species here.
Observations show that the Achatina species are mainly found in plantations and near villages. They can be found everywhere, especially after heavy rains. Outside the rainforest, in the savanna areas, large snails are much rarer. During the dry season, which can take up to four months, they burrow. The apertura (mouth) is closed with an epifragm. In this way, they can survive a period of low moisture and food. In addition, they are thus protected against grass fires. When the first rains fall, the snails become active again.

Agate snails are largely found in low-lying areas. In the mountains and plateaus in Central Africa, the number of species and the population density decrease from 1200 meters. They cannot be found above 1500 meters.
Agate snails are eaten in all regions visited by the expeditions. They are thrown alive into a kettle of boiling water covered with green banana leaves. After boiling, wait for the water to cool. The snail is then removed from the house with a sharp object such as a piece of bone, cleaned and eaten. They are also cut into pieces, seasoned well and fried in oil.
Large houses are used in all kinds of ways, such as to store salt (which cannot be kept dry in the rainforest) or as a drinking cup and spoon.

The strength of the house provides a safe shelter for the snail. This also caught the eye of the people who adopted it in their customs and traditions. Children often wear around the wrist or hip a chain with snail shells. This is not a decoration but a talisman to ensure that the children can always find a safe place when danger threatens.
Some tribes such as the Logo, Baka and Mondo make chains that consist of round discs of an inch in diameter made from the houses. This is a job that requires a lot of patience. The houses are broken with a stone. A hole is made in the center of the pieces. Forty or fifty pieces are then strung on a chain and the edges are worn away by sanding it back and forth over a stone until it is nice and round.

Species described

Despite the size of the former Belgian Congo, the number of species of agate snails is limited, although no expedition to the Katanga region had been carried out at the time of publication. It is also noted that no species is found in both rainforest and savanna.

The following species are described (with the names used in the book):

Achatina bandeirana

Achatina bandeirana (Morelet, 1866)

Location: Savanna from Banza Manteka (between Matadi and Lukungu) and Kunga
Maximum length: 143mm, diameter: 72mm

This species is very similar to Achatina balteata. Achatina balteata var. infrafusca described by Martens based on shells from Banana actually turns out to be Achatina bandeirana.
Achatina tincta

Achatina tincta (Reeve, 1842)

Location: Banana, Leopoldville (Kinshasa), Ile de l'elephant, between Stanley Pool (Pool Malebo) and Kwamouth, Malela, Moanda. San Antonio (Angola) and Brazzaville, Pays M'bagba and Fort Rousset (Congo-Brazzaville).
Maximum length: 101mm, diameter: 45mm

The drawing is very variable. The species Achatina oblitterata appears to be only a mutation of Achatina tincta. Both color forms occur together. This is a fairly common species that can be found under dry leaves where they hide and feed on plant debris.
Achatina pfeiferri

Achatina pfeiferri (Dunker, 1845)

Location: Zambi
Maximum length: 35mm, diameter: 15mm

The specimens examined differ from the type specimen and are likely a local subspecies called Achatina pfeiferri eugrapta.
Achatina sylvatica

Achatina sylvatica (Putzeys, 1898)

Location: Stanleyville (Kisangani), Mobeka, Nouvelle Anvers (Makanza) along the Congo River.
Maximum length: 41mm, diameter: 20mm

This species has an evenly colored mutation called 'unicolor', but the striped specimens also have a wide variety of markings: from many stripes to just a few dots. In Stanleyville (Kisangani), the snails were found among the grass.
Achatina weynsi

Achatina weynsi (Dautzenberg, 1899)

Location: Bumba, Nouvelle Anvers (Makanza) along the Congo River.
Maximum length: 114mm, diameter: 60mm

This species resembles Achatina tincta but is found in a distribution area far from the described habitat of this species. The habitat is adjacent to that of Achatina schweinfurthi. The pattern on the house is often striped in different thickness. Some specimens even have an almost solid color. A mutation 'rosaxis' has been found in which the stripes are not chestnut colored but cinnamon colored.
Achatina schweinfurthi

Achatina schweinfurthi (Martens, 1873)

Location: Eastern Congo: in forests on the flanks of Mt. Baginze and Mt. Ruzenzori, Andetei region, west of the Semliki river, Nsendwe, Lokandu, Piani Kapuri, Ponthierville (Ubundu), Stanley Falls (Boyoma Falls), between Mawambi and Avakubi, Niangara, Medje
Maximum length: 171mm, diameter: 83mm

Achatina schweinfurthi rhodacme

Achatina schweinfurthi rhodacme (Pilsbry, 1919)

Location: Stanleyville (Kisangani), Lubutu
Maximum length: 150mm, diameter: 72mm

This subspecies (left) was described by Pilsbry in which he also determines 2 mutations, namely rhodostemma (middle) and levior (right).
Achatina rugosa

Achatina rugosa (Putzeys, 1898)

Location: In the rainforest on the right side of the Congo River in Micici, Musungu Kifuluka, Nsendwe, Lokandu, Ponthierville (Ubundu) and Stanley Falls (Boyoma Falls)
Maximum length: 106mm, diameter: 52mm

Achatina iostoma is possibly a synonym for this species.
Achatina osborni

Achatina osborni (Pilsbury, 1919)

Location: In the rainforest near Masisi
Maximum length: 141mm, diameter: 66mm

Described by Pilsbury and named after Professor Henry Fairfield Osborn, President of The American Museum.

Other species found in the former Belgian Congo

Achatina balteata (Reeve, 1849) - banks of the Gambia River, Pays M'Bagha, M'Baiki (Congo-Brazzaville)
Achatina glaucina (Smith, 1899) - Mt. Zomba
Achatina graueri (Thiele, 1911) - Kwidjwi Island
Achatina greysi (Da Costa, 1907) - between the Lualaba and Lufira rivers
Achatina nyikaensis (Pilsbry, 1909)
Achatina obscura (Da Costa, 1907) - between the Lualaba and Lufira rivers
Achatina schoutedeni (Dautzenberg and Germain, 1914) - between Sampwe and Kiambi
Achatina stuhlmanni (Martens, 1892) - rainforest west of Ituri
Achatina transparens (Da Costa, 1907) - between the Lualaba and Lufira rivers
Achatina virgulata (Da Costa, 1907) - between the Lualaba and Lufira rivers
Achatina wildemani (Dautzenberg, 1907) - Mangay along the Kasai River
Achatina zebriolata (Morelet, 1866) - Mangay along the kasai river but also in Angola: San Antonio, Malagne, Malash

A species that may be found in Congo:
Achatina ellioti (Smith, 1895) - near Lake Albert and Lake Edward (Uganda)