A preliminary survey of ground dwelling invertebrates
in the Humid Tropic Biome at the Eden Project, Cornwall.
Peter Smithers1 Catherine Trodd 2 & Elizabeth Lane 3
1
& 3 School of Biological Sciences, University of Plymouth.
2
Eden Project.
Introduction
Tropical glass houses are well known as habitats that support small assemblages of exotic tropical
invertebrates. These tend to be members of a small group of generalists that have been transported
around the globe by human activities. The construction of the Eden biomes provided an opportunity to
study the establishment of such a tropical fauna but on a much larger scale than has previously been
possible. It also provides an opportunity to monitor the invasion of the biome by species from the local
invertebrate fauna. This survey is designed to provide an initial insight into the ground dwelling
invertebrate community that is establishing inside the biome and highlight any taxa that are potentially
problematic.
Methods
The survey was initiated in the autumn of 2002 using both pitfall traps and Tullgren funnel extraction
of litter samples.
A total of 20 sample stations were selected to provide an even coverage of the biome floor area.
At each station a set of pitfalls were installed, these comprised two plastic cups set side by side over
which a square of transparent plastic was supported on metal tent pegs in order to prevent flooding of
the traps by the irrigation system. The cups were half full of 0.1 % Propylene phenoxetol in 1: 2
propan diol, which acts as a bactericide and thus prevents decay of the catch , it is also non toxic to
mammals and thus was not a hazard to visitors.
The pitfall traps were emptied every 7 days over a two week period.
Ten litter samples were also taken at selected pitfall sites and transported to the University of Plymouth
were they were placed in Tullgren funnels and left for seven days to extract the invertebrates.
Invertebrates were identified as far as possible using the keys available. Most of the macro
invertebrates were taken to species , while the micro arthropods were divided into morphologically
distinct groups.
Results
The following list details those invertebrates that have been identified to species and provides brief
notes on their natural history.
Isopoda
Armadillidium nasatum Budde-Lund, 1885.
This is a common synanthropic species across most of Europe and the eastern seaboard of the USA,
where is often recorded from gardens, garden centers and glass houses (Oliver & Meechan, 1993). It
was the most abundant invertebrate in the pitfall data set and is common through out the HTB.
Molluscs.
Gastropoda, Helix aspersa. The common garden snail.
This is a widely distributed species that occurs in a wide range of habitats (Cameron & Redfern, 1976).
Symphyla
Scutigerella immaculata
This symphylan is common in gardens, cultivated land and green houses (Hopkin & Roberts 1988).. It
is known to damage the roots of horticultural crops by eating root hairs but low population densities are
not detrimental (Grantwick, 1992).
Myriopoda,
Diplopoda, Oxidus gracilis
A cosmopolitan hot house species that is distributed across Europe, the Americas and Japan (Blower
1985). It has also been recorded from hot houses in Kew gardens (Blower 1985).
Chilopoda Lithobius varigatus.
This is a common British species of centipede that is found in a wide range of rural habitats but is often
associated with quarries. This centipede is likely to be a member of the external fauna (Barber &
Keay,1998).
Chilopoda Haplophilus subteraneus.
This is a common soil dwelling centipede which is wide spread in southern Britain (Barber &
Keay,1998).
Arachnida
Araneae,
Salticidae, Hasarius adansonii
This tropical species of jumping spider occurs in hot houses around the globe. It is sexually dimorphic
with distinctive black and white markings on the male while the females are a dull brown (Murphy &
Murphy 2000).
Anapidae, Psuanapis sp.
This genus is widespread throughout the tropics but are rarely encountered. They inhabit leaf litter and
moss on the forest floor. The species collected is not P. Pavoculus which is the most frequently
recorded species and may be new to science (J Murphy, pers com). Specimens of males would be
required to resolve its identity.
Oonopidae, Ischnothyreus sp. Triarius sp?
Both of these genera are widespread throughout the tropics and sub tropics (Dippenar-schoeman &
Jocque 1997) but Triarius has not been recorded from SE Asia (Murphy & Murphy 2000). They occur
in forest litter and have been reported from glass houses in Britain (Jones Walters 1998).
Pholcidae, Pholcus opilionoides
This species is usually fond in rock crevices or caves in southern Europe but has been recorded inside
buildings (Roberts 1995).
Thjeridiidae, Araearanea tepidariorum
A tramp species that has been introduced to Europe from the sub tropics. It occurs outside in southern
Europe but is restricted to hot houses in the north (Harvey, Nellist & Telfer, 2003).. This species is
widespread around the edge of the biome were it makes a conspicuous web attached to the girders.
Linyphiiidae, Halorates reprobus
A coastal species that is restricted to northern Europe. It is normally found on saltmarshes, rocky or
muddy shores were it occurs beneath rocks or tidal litter (Harvey, Nellist & Telfer, 2003). This spider
has certainly invaded the biome from the surrounding environments but its occurrence in a heated
system is unusual.
Linyphiiidae, Bathyphantes gracilis
This ubiquitous species occurs in a wide range of habitats were it produces a sheet web amongst the
base of low vegetation (Harvey, Nellist & Telfer, 2003). It disperses by ballooning and has invaded the
biome form adjacent habitats.
Insecta
Dermaptera,
Marava arachidis (Yersin) The Bone House Earwig.
This species was first recorded at the beginning of the last century from warehouses and factories
where dried organic materials were stored. M arachidis is another tramp species that is now established
in all of the warmer parts of the world (Marshal & Haes 1988).
Coleoptera,
Carabidae, Nebria salina
A common carabid species that is often associated with drier habitats. (Lindroth 1974) This appears to
be another local species that has invaded the biome.
Dictyoptera,
Periplaneta australasiae
This cockroach is found across the globe, occurring in house and building in temperate regions and
outside in the tropics (Cornwell 1968).
Hymenoptera
Paratrechina longicornis, Crazy ant.
This species is a common pest in houses in the tropics and sub tropics (report for Eden from NHM
London, 2002).
Solenopsis sp. Thief ants.
This is a large genus which has a global distribution . They build their nests within the nests of other
ants and steal food collected by their hosts (Bolton & Colloingwood, 1975. Bolton 1994). The species
Solenopsis fugax has been recorded from southern Britain in the past but as the plants in the biome are
of a cosmopolitan origin, the identity of these specimens need conformation.
Pitfall Traps.
The most abundant organism in the samples was the woodlouse Aramadellidium nasatum with 911
individuals collected in the sampling program. Its distribution is very patchy occurring in 18 of the 26
samples with numbers ranging from 0 to 300 per sample. The next most abundant species was the
earwig Marva arachnis with a total of 21 individuals, occurring in 13 samples all at low numbers
between 1 & 4. The only other invertebrate to occur in any number was Periplaneta australis with 10
individuals from 5 samples. This is certainly an under estimate of numbers in the biome. All of the
remaining marco invertebrates were present in low numbers, 1 to 3 individuals from only 2 or 3
samples.
Litter Samples.
Samples were taken of the limited litter layer that exists in the biome along with samples of the bark
mulch that has been spread under many of the plants. Of these samples 1 – 4 consisted of leaf litter
whilst samples 5 – 10 were composed of bark mulch. Only one litter sample (taken from an area of
deep litter) contained an appreciable number of micro arthropods including large numbers of
prostigmatid and mesostigmatid mites. The rest contained very low numbers of organisms. The bark
mulch varied considerably with total numbers of individuals ranging from 16 to 392. These contained
low numbers of prostigmatid and mesostigmatid mites.
Discussion
The micro arthropod community on the biome floor appears to have a low diversity and a patchy
distribution. This is probably due to the very limited nature of the litter layer that is present. In order to
promote a more diverse community the litter layer should be allowed to accumulate naturally. Micro
arthropods play an important role in recycling the nutrients tied up in the litter on a forest floor and a
more robust invertebrate community would enable them to be recycled more effectively.
The macro invertebrate community on the floor of the Humid Tropic biome is also low in both
diversity and abundance. It is principally composed of tramp species that have been introduced with the
plants. These species are cosmopolitan and have been spread around the globe by human activities.
It is however interesting to discover a rare and unusual Anapid spider amongst these suggesting that
this species may also be common in hot houses but have been previously overlooked due to its small
size.
With the exception of the spider Araearanea tepidariorum none of the predatory invertebrates are
abundant or widely distributed within the biome. These could play an important role in limiting the
numbers of potential pest species but in the absence of a litter layer these predators are unlikely to
reach numbers were they can exert a significant effect.
There are few invading species from the external environment but those that have been recorded are
either very common or very mobile organisms. The sacristy of members of the external fauna is
unexpected given the large volume of visitor traffic in and out of the biome and the open nature of the
vents. Conditions inside the biome are probably unfavorable to many would be colonists but as the
The only species that may be of some concern are the Australian cockroach Periplaneta australasiae
and the Crazy ant Paratrechina longicornis,. Both of these can be severe pests of domestic kitchens
and with the close proximity of the restaurant to the biome extreme vigilance is advised to prevent
them gaining access to this area.
Acknowledgments
We would like to thank the Eden project for permission to carry out the work and John Murphy for
identifying the Anapid and Oonopid spiders. Also Jenny Taylore-Alle for generating the map.
References
Blower (1985). Millipedes. Synopsis of the British Fauna. Field Studies Council.
Barber & Keay,(1998). Provisional Atlas of the Centipedes of the British Isles. Biological Records
Centre.
Bolton & Colloingwood, (1975). Handbook for the indentification of British Insects, Hymenoptera,
Formicidae. Royal Entomological Society.
Bolton (1994). Identification Guide to the Ant Genera of the world. Harvard University Press.
Cameron & Redfern, (1976). British Land Snails. Synopsis of the British Fauna. Field Studies Council.
Dippenar-schoeman & Jocque (1997). African Spiders, an identification manual. ARC, Plant Protection
Institute.
Grantwick, ED.(1992). Crop Pests of the UK. ADAS, MAFF , Chapman & Hall.
Hopkin & Roberts (1988). Symphyla. The least studied of the most interesting soil animals. Bulletin of
the British Myriopod Group. (5).
Harvey, Nellist & Telfer (2003). Provisional Atlas of British Spiders. JNCC.
Jones Walters (1998). Keys to the Families of British Spiders. AIDGAP, Field Studies Council
Lindroth (1974). Handbook for the indentification of British Insects, Coleoptera, Carabidae. Royal
Entomological Society.
Marshal & Haes (1988). Grasshoppers and allied insects of Great Britain and Ireland. Harley Books.
Murphy & Murphy (2000). An Introduction to the Spiders of SE Asia. Malaysian Nature Society.
Oliver & Meechan, (1993). Woodlice. Synopsis of the British Fauna. Field Studies Council.
Roberts (1995). Spiders of Britain and Northern Europe. Harper Collins.
Pitfall trap station
1
Symphyla
Diplopoda
Chilopoda
Chilopoda
Isopoda
Aranae
Aranae
Aranae
Coleoptera
Coleoptera
Collembola
Dermaptera
Dictyoptera
Lepidoptera
Oligochaeta
Gastropoda
Gastropoda
Scutigerella
immaculata
Oxidus gracilis
Haplophilus
subteraneus
Lithobius varigatus.
Armadillidium
nasatum
Bathyphantes gracilis
Hasarius adansonii
Halorates reprobus
Curculionid sp.
Nebria salina
Entomobyridae.
Marava arachidis
Periplaneta
australasiae
Lepidoptera larva
Oligochaeta
Mollusc egg
Helix aspersa
Total individuals /
pitfall
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
1
2
1
26 Total
No
Indivi
duals
1
1
4
2
2
4 227
0
0
1
3
35
0
9
1
67 300
3
1
1
6
0
0
0
1
17 200
0
3
0
0
1
33 911
1
3
1
1
1
1
4
2
2
3
1
1
1
1
2
1
1
1
1
1
2
3
2
4
1
2
7 233
1
2
6
1
1
1
Apendix 1. Abundance of taxa recorded from pitfall traps.
6
1
3
37
0
14
2
68 305
6
4
3
8
2
2
1
1
18 200
0
3
0
3
1
41
1
4
1
1
0
3
21
10
1
4
4
3
Order
Taxon
Prostigmata
Tetranychidae
Mesostigmata
Cryptostigmata
Oppia sp.
Phthiricaridae
Astigmata
Uropdina
unknown
Sminthuridea
Poduridea
Entomobryoidea
Oxalis gracilus
Aphididae
nymph ?
Coccoidea
Pholcus
opilionoides
Pseudanapis sp
ARANEAE
Ischnothyreus sp
ARANEAE
Triarius sp?
ARANEAE
Armadillidum
ISOPODA
nasatum
NEMATODEA
species ?
HYMENOPTERA Solenopsis sp
COLEOPTERA Larvae
Cecidomyiidae
DIPTERA
Scaridae
DIPTERA
PSCOPTERA
DERMAPTERA nymph ?
PAUROPODA
LEPIDOPTERA Larvae
Scolopendra imm
CHILOPDA
Geophilomorpha
CHILOPDA
imm
Total individuals
per sample
ACARI
ACARI
ACARI
ACARI
ACARI
ACARI
ACARI
ACARI
ACARI
COLLEMBOLA
COLLEMBOLA
COLLEMBOLA
DIPLOPODA
HEMIPTERA
HEMIPTERA
HEMIPTERA
ARANEAE
Station 4 Station 8 Station
11
0
3
0
0
0
1
0
6
1
0
1
2
0
4
1
1
4
9
0
0
1
0
0
0
0
0
0
0
1
0
0
2
0
0
4
1
0
0
0
0
3
0
0
0
0
0
0
0
0
0
0
Station Station Station 18
13
16
303
1
was too
24
0
decomposed
111
0
to I.D.
12
0
0
0
73
5
10
0
0
0
7
0
0
0
7
2
10
4
0
0
1
0
1
0
0
0
0
0
Station
20
16
0
12
1
0
5
0
0
0
0
8
2
0
0
0
0
0
Station
21
4
0
1
3
1
3
0
0
0
0
24
11
1
1
0
0
0
Station
22
25
0
24
2
5
212
0
1
10
0
27
12
0
0
0
0
1
Station
23
30
0
11
44
1
61
5
0
30
1
41
23
0
2
0
0
0
Total individuals
per taxon
382
25
166
65
12
373
16
1
47
2
111
67
1
7
1
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2
1
1
0
0
0
0
2
2
0
0
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
8
1
0
0
6
0
0
1
0
1
1
3
0
0
0
0
0
0
0
0
0
9
0
10
1
0
0
0
0
0
0
0
4
0
1
6
1
0
0
0
0
0
0
0
0
2
0
0
0
2
0
0
1
3
31
1
1
0
0
0
1
0
0
0
*4
46
12
15
7
1
6
3
0
1
1
4
1
28
17
576
16
64
61
331
285
Apendix 2. Abundance of taxa in litter samples.