Nesticella mogera
(cave-dwelling spider)

This small web-building spider, a native of Japan, the Caucasus and the Far East, has only recently been introduced to Kauai in Hawaii, where it has replaced the endemic cave-dwelling spider, Erigone stygius.

It has also been introduced to some European countries, apparently via the tropical plants trade, and appears to be limited to tropical greenhouses, zoological gardens and garden centres where the conditions are warm and humid. 

N. mogera was discovered in Japan, with a possible natural range in the Caucasus and the Far East, and it has been introduced to Hawaii (Kielhorn, 2009).

It is thought to have the widest distribution range of all nesticids (Marusik and Guseinov, 2003).

N. mogera has been introduced to some European countries, apparently via the tropical plants trade, and appears to be limited to tropical greenhouses, zoological gardens and garden centres where the conditions are warm and humid. Wherever similar routes in exist, there is the potential of the species being introduced to the wild if local conditions are favourable (Rozwalka et al., 2013).    

N. mogera has been described as a cosmopolitan species that occurs in surface habitats and caves (Zhang and Li, 2013).

In Japan, N. mogera is found in leaf litter, the burrows of moles, and rarely in caves (Gertsch, 1973; Kielhorn, 2009). On the Hawaiian Island of Mauai, it is found in caves and in Fiji it has been found in bushes near a mangrove swamp and in jungle litter (Kielhorn, 2009). In South Korea it has been recorded in paddy fields, and ruderal vegetation in agricultural, industrial and residential areas (Kielhorn, 2009). In Azerbaijan it has been found in leaf litter on the edge of a relic forest (Rozwalka et al., 2013). In China it has been found in caves and under rocks near to caves (Zhang and Li, 2013).     

Rozwalka et al. (2013) describe its preferred habitat as in warm humid places, under stones and pieces of wood, and in thick forest litter and occasional caves. It is suggested that N. mogera may be a thermophilious and hygrophilious species, preferring a deep litter and places under stones (Bielak-Bielecki and Rozwalka, 2011).

Where spiders such as N. mogera have been introduced, they tend to occur more frequently inside buildings, on outside walls, in greenhouses and in warehouses etc. (Rozwalka et al., 2013).

Genetics

Somatic cells of male and female Nesticus mogera [Nesticellamogera] have a chromosome number of 22 and 24, respectively (Wang and Wang, 1998). 

The genus Nesticella is polyphyletic, with several sub-clades and two clades distinctly separated from each other by the barrier of the Red River Fault in South China (Ballarin and Li, 2015). Analysis suggests that ancient colonisations followed by extinctions have occurred in the past (Ballarin and Li, 2015).

Reproductive Biology

N. mogera displays sexual dimorphism. The female is larger (Nentwig, 2016) and the male has specialised pedipalps (Gertsch, 1973).

Little information specific to reproduction in this species has been identified. However, as with other spiders, it is likely that the male locates the female via pheromones and deposits sperm onto a small web and then transfers this to the female genitalia using his pedipalps (Larsen, 2016). Usually, the eggs are fertilised by the sperm as they are laid a week or more after mating (Larsen, 2016).

The N. mogera female spins a round ball-like cocoon around her eggs once they are laid, and carries the cocoon with her (Spinnen Forum, 2015). Other members of the family Nesticidae carry the egg cocoon attached to their spinnerets, with the cocoon sometimes being larger than the female (Nieuwenhuys, 2010). Photographs available on Spinnen Forum (2015) suggest that this is the same in N. mogera.

Activity Patterns

Nesticus mogera [Nesticella mogera] in caves in Hawaii are described as spinning sloppy inverted webs between adjacent protuberances and in cracks in the walls (Howarth, 1978).

Nutrition

Like other spiders, it is assumed that N. mogera preys on small invertebrates.

It is assumed that N. mogera will be predated by other invertebrates, including other spiders, and by small mammals and birds. 

There are 29 species of Nesticella listed by ADW (2016) and the Encyclopedia of Life (2016).

Leg setae have been proposed as a diagnostic for the family Nesticidae (Grall and Jäger, 2016).

Phylogenetic analysis has suggested that there may be cryptic species currently defined as N. mogera (Zhang and Li, 2013).

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

No information on detection, prevention or control of N. mogera have been identified.

There is a general lack of information on N. mogera. Information on most aspects of the life history of this species would be beneficial, especially if it has a negative impact on native species. 

More investigation on potential cryptic species currently assigned to N. mogera would also be beneficial.

Information on detection of this species and any potential methods of control is also sparse.

10/05/16 Original text by: 

Vicki Cottrell, Consultant, UK