Download Insects-most common insects found on Ascension Island Prepared

Insects-most common insects found on Ascension Island
Prepared by Natasha Williams Conservation Assistant.
On Ascension there are a wide species of insects which is also known as Invertebrates.
Spiders
On Ascension there have been records showing up to 30 species of spiders found on the Island
that also includes a spider that is family to the Black Widow . It is called the Brown. Here below
are a few of the common species found around the Island and that are seen everyday.
Agelenidae – funnel-web spiders
Agelenids are long-legged, dark-coloured, fast-moving spiders in which the anterior part of the
carapace is parallel-sided and cut of square in front (cf filistatids). They make untidy webs that
lead to a funnel in which the spider lurks, in crevices or under rocks; the web is often built up
over the surface of the rock and gets encrusted with dust. Two species are recorded from St
Helena and one from Ascension.
Tegenaria domestica. This spider has travelled around the world with humans. On Ascension it
was recorded at the end of the 19th century in holes in the rocks at around 500m on Green
Mountain.
Araneidae - orb-web spiders
Araneids are one of the few groups of spiders that build beautiful orb-webs to catch their prey.
The webs are usually more or less vertical and can be seen stretching between branches of trees
and shrubs. The spiders themselves are mostly broad-bodied, with globular abdomens. One
specie has been recorded on Ascension Island.
Araneus theisi. This is the only orb-web spider on Ascension. It is a widespread tropical species
which could have reached the island either naturally or by ship.
Gnaphosidae – mouse spiders
Gnaphosids are free-living, dull-coloured, nocturnal hunting spiders that retreat into silken nests
under stones by day. The abdomen is covered in fine hairs reminiscent of mouse fur, which may
glisten with metallic brightness. The front (outermost) spinnerets are long and cylindrical and are
used to lay down bands of silk which immobilize the prey.
Ascension seems to have six species; several of these cannot yet be fully identified, but
probably include members of the genera Drassodes and Nodocion. This is one of the few groups of
invertebrates in which diversity is apparently higher on Ascension than St Helena.
Pterochroa funeral. This spider is up to 12mm long brown, with black radiating marks on the
carapace. The eight eyes are in two rows, both curved backwards: the central pair in the second
row are not circular. On St Helena the species is known only from one male found by Melliss and
a female found by the Belgians just of Flagstaff. It has been recorded from Ascension, but seems
likely to have been introduced to that island from St Helena.
Trachyzelotes Jaxartensis This species occurs in both lava and cave sites on Ascension and may be
indigenous.
Zelotes inauratus This species was found near South Gannet Hill. It is native to the Mediterranean
region and may perhaps have reached Ascension naturally.
Linyphidae-sheetweb weavers and dwarf or money spiders
These are small or very small spiders which build sheet-like webs, usually close to the ground;
some make a dome over the sheet. The linyphiids are highly diverse and successful in the North
Temperate Zone but relatively scarce in the tropics. Ascension has three endemic species, one of
which constitutes an endemic genus; the other two have not been fully identified.
Catonetria caeca We found this spider in a cave in 1990 and again in 1995. It is minute, blind and
white probably now incapable of living outside caves, but its ancestors doubtless reached
Ascension by ballooning.
Loxoscelidae-brown spiders
Loxoscelids have six eyes in well separated groups of two. They are bristly, free-living spiders
with drab colouration, living under stones or in crevices; some species come into houses. They
weave a sheet of sticky silk in which they entangle insects, but also tend to roam at night. Their
bite is very poisonous, and the wound often ulcerates, becomes infected and leaves disfiguring
scars. One specie has been recorded on Ascension Island.
Loxosceles refuescens. On Ascension we found it in Georgetown. Elsewhere it occurs in the
Mediterranean region but also on many oceanic islands.
Lycosidae-wolf spiders
The lycosids are free-running, ground-living spiders that hunt their prey by day, often in
sunlight. They have four tiny eyes just above the chelicerae, two large ones above, and two
smaller ones further back on the sides of the head (salticids, another group with two large
forward-facing eyes, lack the four tiny ones below). Lycosids often disperse by ballooning –
letting out a silken thread which gets caught in the wind-and they have successfully colonised
many oceanic islands.
Lycosids are not easy to identify and the boundaries between the genera are often
obscure. Only one specie has been found on Ascension.
Paradosa inopina. This small wolf spider is widespread in Africa and probably colonized
Ascension naturally.
Oecobiide- Oecobiids
Oeciibides are very small, squat spiders with a broad carapace and eight eyes closely grouped on
top of it. They are gr ound-living, web building and feed largely on ants. They build a small, flat
star-shaped web in cervices, but sometimes wander. Three species in the genus Oecobius have
been recorded fromSt Helena and one of these also from Ascension; they may well have arrived
by humans.
Oonopidae-oonopids
Opopaea euphorbicola. This is one of the few endemic species found on Ascension; it has close
relatives on the African continent and on the North Atlantic islands. O. euphorbicola is about 1.5
mm long and unifor m pale orange. The carapace narrows smoothly forwards to the green eye
region and the abdomen is covered above and below by rigid plates (scuta). O.euphorbicola occurs
in the desert areas of the island.
Prodidomidae-prodidomids
This is a small family of little known spiders sometimes included in the Gnaphosidae. They are
small, hairy spiders with extremely long spinnerets and long, widespread chelicerae. They seem
to be well adapted to desert, coastal areas, and we suspect that they may be capable of dispersal
by rafting. On St Helena there is one endemic species in the genus Zimirina. Ascension has two
apparently endemic species in the genus prodidomus, and on the Mars bay lava flow we found
immature spiders that seem to belong to Zimirina and to a related genus, Zimiris.
Prodidomus clarki. This species was discovered by Eric Duffey during his ecological survey of
Ascension in 1958.
Prodidomus duffeyi. This species was also found by Eric Duffey.
Salticide- jumping spiders
The jumping spider s are extremely diverse in warm parts of the world. They have eight eyes, but
two of these are enormous and face forwards, so that the spider’s gaze can be disconcertingly
anthropomorphic. Salticids have excellent vision and are active during the day, often in the
sunshine. Hunting is by means of long pauses, quick darts and dramatic leaps. Many species
have bright colour patterns and metallic glints. Salticids are evidently excellent natural
dispersers. They have been collected at high altitudes in the air and were well represented
among early colonists of Krakatua, and in the endemic fauna of other islands; however, some
species also seem to have been carried around the world on ships.
Of ten species recorded from St Helena seven are endemic and four of these-which
evidently evolved on the island from a single colonising stock-the Belgians created the endemic
genus Paraheliophanus; however, this is closey related to the genus Icius and may eventually be
suppressed. Two other endemic species in the genus Pellenes doubtless are evolved on the island.
Four species of Salticids have been recorded from Ascension; these are all widespread and three
of them also occur on St Helena.
Plexippus paykulli. This species is larger than the other Salticids on Ascension. The male is up to 9
mm long and has a striking pattern of black and white bands running the length of the body; the
female is somewhat larger and lacks the clear striped pattern. P.paykulli has been found both on
the main island and on Boatswainbird Island. The species is widespread in the tropics.
Menemerus bivittatus. This species is up to 10 mm long and was noted by Melliss as the Black and
White Money Spider common in houses on the island. It is usually associated with humans and
now occurs throughout the tropics.
Scytodidae- spitting spiders
These nocturnal spiders have long delicate legs and a high rounded thorax which slopes down in
the front; under the dome is a pair of large glands from which the spiders can squirt fine strings
of a sticky secretion to immobilize their prey. There may be three species in the genus Scytodes
(S.velutina, S.fuscata and S. similis) on St Helena and one (so far unidentified) on Ascension; none
of them are endemic.
Tetragnathidae-tetragnathids
Tetragnathids make orb-webs similar to those of araneids but with less dense spiral threads and a
hole at the centre. There are five species on St Helena, four of which are endemic; two of these
are placed in an endemic genus. There is only one tetragnathid on Ascension.
Dyschiriognatha argyrostilba. This species probably reached Ascension naturally, as it is the
African representative of widespread genus with oceanic distribution. It is intriguing that on St
Helena there is an endemic species (D.atlantica) which could be derived from the same stock.
Pholcidae-daddy long legs spiders
Pholcidae are delicate spiders with extremely long legs. They hang upside down on loose threedimensional criss-cross webs in holes and damp places. Three species have been found on St
Helena but there is no evidence that any are indigenous. Six species have been found on
Ascension, but the four that are fully identified are widespread and unlikely to be indigenous.
The larger number of species on Ascension probably reflects the adaptation of pholcids to barren
lava habitats with many underground spaces. One species found in a cave on Ascension may be
adapted to cave life and even be endemic; but specimens is in poor condition, but daddy -long
have been seen in people’s houses in the bath tubs.
Theridiidae – combed-footed spiders
This large family includes spiders of many different shapes, but some have a conspicuously
globular abdomen; a number species are poisonous. Theridiids are good natural dispersers and
have endemic and non-endemic forms on many islands, but some are associated with dwellings
and likely to be dispersed with human belongings. This is the most diverse spider family on St
Helena, but four species are known from Ascension.
Latrodectus geometricus, Brown Widow. The widows are large (up to 16mm long) poisonous
spiders; they have a globular abdomen with red markings. Female widows are sedentary and
may bite if molested; males wander but do not bite. These spiders make tough, tangled webs and
the spherical white egg sacs hang in the web. The rather similar spiders in the genus Steastoda are
also represented on both islands; they do not have red markings and are not considered
poisonous. The Brown Widow is brown to black with a red mark on the underside of the
abdomen; it is found in dry rocky places. The bite of this spider is poisonous, although not as bad
as that of the next species.
Ants
On Ascension Island we have ants. Ants are small or medium sized social insects with the
separate wingless worker caste as well as functional males and females. It’s in group of insects
called Hymenoptera that also involves the wasps, bees and parasitic hymenopterans. The narrow
‘waist’ found in most Hymenoptera takes a special form, being interrupted by a conspicuous
node or scale; the antennae are conspicuously elbowed. Nine species of ants have been recorded
on Ascension as the same number on St Helena. There is no evidence, however, that ants were
present on either island in pre-human times. Most species are probably introduced. Although
ants are capable of rafting over short distances they have typically failed to achieve natural
colonization of very isolated islands. Of the nine species on St Helena eight are well known
‘tramp’ species that have become almost cosmopolitan as a result of being transported by man;
the ninth has also been disturbed in this way, though less extensively. Ants are abundant on
Ascension, although they are absent (or present in low numbers) at the most barren lava sites on
Ascension; one species is present on Boatswainbird Island as well as the main island. Since antsacting collectively-are efficient predators on many other insects, it seems likely that the arrival of
ants - and in particular Pheidole megacephala-on Ascension may have led to the extinction of many
invertebrates that lived on them in their pristine state.
ISOPODA -Woodlouse
Most isopods are aquatic but the woodlouse can live in moist places on land. They are flattened
but also somewhat domed animals, with two pairs of antennae (although only one pair is
conspicuous) and seven pairs of legs. They are typically oval and are thus easily distinguished
from millipedes. Which have more legs and are much more elongate. Unlike the amphipods,
woodlice do not hop, but walk relatively slowly; some of them can roll up into an armoured ball.
We make no attempt to describe the different families or the individual species, since most
woodlice are hard identify unless one is a specialist. However, we discuss the endemic or
probably indigenous species and list all the others, since the treatment of woodlice by the
Belgians is seriously out of date.
The Ascension Woodlice are intriguing. Until recently, only nine species were known
from the island and all were considered to be certainly introduced by man.
Armasillidae-armadillids
Cubaris murina. This species has been found in Wideawake colonies and in the very barren lava
of Lava Lake (which has traces of old guano). It is a widespread tropical species and we suspect
that it may have reached the island naturally with seabirds.
Pseudolaureola atlantica. This species, collected by us on St Helena and by Duffey on Ascension, is
also known from South Africa and may have been introduced to both islands.
Venezillo parvus (ex Sphaerillo parvus) was found on Ascension by Eric Duffey. It occurs in many
islands in the Indian Ocean and was probably introduced to Ascension with plants.
Atlantoscia floridana This is the species recorded from St Helena as Chaetophiloscia paulensis (where
has been found in several parts of the uplands) and from Ascension as Atlantosica alceui. It also
occurs in Florida and South America, and was probably introduced to both islands.
Littorophiloscia tropicalis On Ascension we found this specie in 1990, on and near the shore at
Shelly Beach. The L. tropicalis is a salt -tolerant species now recognized as occurring on coasts in
many parts, of the tropics; it probably colonised Ascension by dispersal on driftwood, and
possibly also be indigenous on St Helena.
Niambia duffeyi Eric Duffey found two males of this species and we found two females, on lava at
Letterbox and inland from Shelly Beach. This species and the next, which are apparently endemic
to Ascension, probably originated from a single colonizing stock that reached the island from
South Africa
Hoverfly
Butterfly
Wasp
Cockroach
Centipede
Ladybirds
Mosquito
Scorpions
Fly
Fish
Around Ascension Island in the waters we have quite a few species of fish inshore fish such as
the Octopus, the Black Durgan and more.
We have the Endemic fish and the Common fish of the island.
Common
The Black Durgan
Also known locally as the Black fish. It is a member of the Trigger family and it’s found in the
tropic waters. Although only off Ascension the black fish is overwhelming unlike anywhere else.
It can be seen in many colours that are brought on by flash light. It is know as a scavenger and is
known to eat most things. At night they sleep on the seabed on their sides. The scientific name for
the Black fish is Melichthys niger
Octopus
Usually amazing masters of disguise, they can change surface texture and colour very quickly,
including going speckled to merge with the surrounding rocks. Sitting completely still, they are
difficult to see. On sand they can look like stones or coils of rope.
Softback Soldier
Known as Soldier fish, Blackbar/Softback or Bastard Soldier. It is a small medium size fish with a
black bar between their heads and bodies; they are seen in groups in caves or under ledges in the
reef. They are seen often mix with squirrelfish and the St Helena Butterflyfish. The scientific
name for this fish is Myripristis jacobus
Hardback Soldier
This fish is a medium size fish that has horizontal striped pink, red and off-white with off-white
fins and tail that gives it a ‘frilly’ appearance. Some of this species have two vertical white stripes.
The scientific name for the Hardback soldier is Holocentrus adscensionis
Bullseye
The Glasseye Snapper, this fish has a distinctive colour and its eyes appear to be reflecting glass.
The Scientific name for the Bullseye is Heteropriacanthus cruentatus
Rock Hind
The rock Hind also known as jack or grouper is sort of a stealthy character, can be seen sitting on
rocks trying to camouflage itself, or moves quickly and discreetly around rocks. It varies in size
from small to quite large the Black blotches on its back among the spots are featured
distinguishly. On occasions fish that is the same size can be seen in waters but without blotches .
The Scientific name for the Rock Hind is E pinephelus adscensionis. Analyses have shown that
Grouper start their lives as females and after a few years of breeding they can change their sex to
male. Usually the female is bigger than the male. The female matures about 3 years and can breed
up to abou t 20 years.
Common Conger
The Common Conger, also known as the Spotted Moray and scientific name for this specie is
Gymnothorax moringa. It usually hides in crevices, but sometimes seen swimming freely; if left alone they
retreat if challenged they bite.
Pompano
This species swims in shallow water close to the surface in groups, sometimes with Needlefish.
They have either black outer edges or black dots at the end of their V tails. They are locally called
Silver fish and the adults can grow to 70cm and are seen in twos and threes in deeper water.
Coalfish
This fish is locally called the Black Jack, it has a high forehead that is the distinctive feature of this
large dark grey fish. Younger ones have olive green backs. They swim quite close, sometimes
swimming at you and veering off at the last moment.
Tuna
The tuna is the favourite game fish, often over 100lbs in weight and several over 200lbs have been
caught off the island over the years. The Yellowfin Tuna is a common species and makes
excellent eating. Many local recipes include Tuna, but in recent years supplies have become more
sporadic.
If numbers of the surface feeding tuna (Yellow-fin) are significantly reduced, so is the
availability of food for seabirds such as the
Sergeant Major
This fish is locally call the Five Finger fish. You can see inquisitively why, which is because it has
five black vertical stripes. Some of the largest sergeant majors are so dark that it is difficult to see
the stripes. They are usually found away from the reef, sometimes in shoals of 20-30.
Shitty Trooper
Parrotfish
This is a fish that is in shape and has a habit but more subtle in colour than its Carribbean
cousins. The male (Blue Dad) is silvery blue when seen near the surface, whereas the female is
browny yellow. They are shy, and difficult to photograph. This fish is also known as the Rockfish
Endemics
Shrimp
There are 74 species of crustaceans known around Ascension, of which 14 are endemic. Another
North American biologist has identified 27 species of marine amphipods around Ascension
Island some are fish invertebrates in rock pools.
Inland from Shelly Beach of east Mars Bay, there are groups of different pools. These
represent an ‘anchialine’ habitat. Pools are water filled crevices that have no surface connection
with the sea, but are salt or brackish and are influenced by tides. The pools are about 50-100m
inland and are evidently connected to the sea underground.
These tiny pools are the only known habitat for two particularly interesting species of
shrimp, which are found nowhere else in the world, they also contain a number of other endemic
animals,as well as clusters of the striking of globular green alga Valonis ventricosa and interesting
coral in the genus Favia. The shrimp probably survive because no predatory fish have managed
to get into this habitat.
The presence of shrimps in the pools was recorded by John Packer in the 1968 edition of
his Ascension handbook, but the first collections were apparently made in 1970 by Douglas S
Rogers, an employee of Pan American World Airways and at the time Curator of the Fort Hayes
Museum of Ascension Historical Society. The first shrimp to be found was named Typhlatya
rogersi in honour of Mr. Rogers, this species is pale pinkish and semi-transparent, and is
abundant in the pools. The other remarkable fact about this specie is that its relatives live mainly
in freshwater subterranean habitats, especially on islands of the Carribean.
The Second species was collected by Mr. Rogers later the same year and named Procaris
ascensionis. It was the first known member of the new family of shrimps, but related species have
been found in similar situations in Bermuda and Hawaii. It is a bright orange in colour and is
larger but less common in the pools than Typhlatya of which it is a predator.
Ascension Goby
This is a very small fish about 3.5 cm and they are difficult to spot as it is very quick and always
moving. It is only found around Ascension.
Ascension Wrasse
This fish is a small bright turquoise and brown, sometimes it is occasionally red striped fish, seen
everywhere on the reef, sometimes in shoals. When in the mating season, they mating behaviour
is sort of like a dance followed by darting in different directions. The male intendance is dark
above with a leaf green dorsal fin.
Cavalley Pilot
These little fish can be found off any reef cliff with their distinctive white spot near the tail. This
spot is fluorescent and shows up in the dark. The Apollo Damselfish is similar to Chromis
multilineata. Found on Ascension only.
LubbocksYellowtail Dameselfish
This species has a distinctive yellow tail that attracts a lot of attention. It is a small fish with a
very dark body which occasionally flashes a brilliant royal blue if closer to the surface. It is found
ever ywhere in small numbers, but can be seen in shoals off reef cliffs. It’s quite an aggressive
little fish, it chases fish much lager than itself, it also is only found on Ascension Island.
Marmalade Razor
The Marmalade Razor is a pretty, pinky orange and turquoise blue vertically striped small fish,
with a pattern of fine red vertical stripes on its head. It is often seen near the seabed in
Comfortless Cove and English Bay, feeding near other fish, including Goatfish, on nutrients
being stirred up. It is only found around Ascension Island.
Mottled Blenny
This fish is about 3cms and these fish are striped browns and fawns and are seen just below the
surface on rocky pools. They are so small and quick, you have to be close to see them.
Old Wife or Seabream
This is a member of the porgy family; the Old Wife looks like a small Brim but has a more
pointed head, a large eye and vertical pale and dark grey/brown stripes extending through the
tail. Have been seen singly or in pairs in shallow water. Found only on Ascension
Splendid Angelfish
This fish is also known as the Angelfish, Resplendent. It is very tiny about 2cms in length, it is a
very pretty, bright blue fish. They live in colonies of about a hundred, they swim within and
above a circle, measuring about a meter in diameter, of light stones with a central hollow. These
fish are found only around Ascension’s coastlines.
White Hawksfish
This small fish can be found in rock crevices. They are pretty when in the light, near the surface,
as the ‘white’ is delicate mauves and pinks, just like mother of pearl. Found only around
Ascension Island.
Dolphins and Whales
Usually Dolphins can be seen around Ascension Island on the way to Boatswain Bird Island and
Porpoise Point playing. The most species seen are the Bottlenose Dolphins. Also around in
Ascension in different parts of the year whales are see in Ascension water usually the
Humpbacks.
Green Turtles
The Green Turtles Comes to Ascension every year between November and July to nest. They
travel all the way from Brazil with the males and mate in Ascension waters and then comes onto
the beaches to lay their eggs. The females can mate with more than one male and can lay as many
as 10 times at intervals of 10-17 days in a mating season. Then they leave and head back to Brazil,
during their time here they have nothing to eat because they only eat a type of sea grass which
grows in Brazil. From the parents leaving then after 50-60 days incubating in the sand the Clutch
hatches and the hatchlings climb up out of the sand and then heads to sea, research have shown
they take 3 weeks to travel to Brazil but at babies they go out into the ocean and nobody knows
what happens between the hatching and when they are dinner plate sizes which is about 10
years.
Hawksbills
Hawksbill Turtles are seen around Ascension waters for some reason they come here, but does
not come on land, therefore when one is seen they are caught, tagged, microchipped and then put
back to sea. It’s a small turtle with a magnificent shell which merges with the environment. It is
sleeps wedged under ledges and this causes white marks on the shell they come from West
Africa.
The Land Crab
Gecarcinus lagostoma, Landcrabs. This large terrestrial crab was the dominant terrestrial omnivore
on Ascension at the time of its discovery by people. Young crabs were fear. The landcrabs
doubtless had significant effects on the native vegetation, and may have determined which
species of seabirds could breed on the main island of Ascension.
As in other crabs, the abdomen of the Ascension landcrab is much reduced and curled
under the thorax. The body and somewhat flattened and the animal can – when – necessary – run
quickly in any direction; normally, however, the movements are slow and deliberate. The
landcrab grows to a carapace length of 8cm and a legspan around 25cm. Two colour phases are
present: smaller individuals are normally red or purple and tend to have the shell granulated
around the front; the largest individuals are generally yellow or orange and the shell is smoother.
On Ascension landcrabs are mainly nocturnal, living in burrows in pyroclastic deposits, but in
high moist areas east of the mountain they can often be found in dark places under bushes
during daytime. They are partial to the fruit of tungies (prickly pears) and probably consume
much vegetable matter. However, they also eat a wide variety of animals when they can catch
them; there is a record of one killing a young rabbit and they occasionally win a fight with a rat.
In the past, eggs and young of seabirds probably suffered a good deal. At present the landcrabs
do little harm to the Wideawakes, perhaps because the fairs are in low -lying arid areas unsuitable
for the crabs; but we have found one Wideawake egg apparently crushed by a landcrab.
Storrs Olson has suggested plausibly that successful breeding of petrels that nest in the
open or in burrows in soft ground may be impossible on islands with numerous landcrabs. Petrel
chicks are left alone by the parents while still young, and are almost helpless; they would be easy
prey for landcrabs. This contrast between the undisturbed seabird community of St Helena, with
large numbers of petrels, and that on Ascension, where only the crevice-nesting Madeiran Stormpetrel was abundant, may, be due as much as to the respective absence and presence of landcrabs
on the two islands, as to differences in the surrounding seas.
Although landcrabs spend almost the whole of their life on land, they have to release
their larvae into seawater. However, the larvae metamorphose into tiny crabs which then quickly
become terrestrial. On Ascension, they then face the daunting task of climbing through the desert
lowlands to the moister uplands where they can find food and avoid dessication. Many
populations of land crabs show annual spawning migrations of the adults to the sea, but it
appears that on Ascension the cycle is less regular. A 19th century record indicated seaward
migration in February and March, and in late March 1963 John Packer noted thousands of tiny
crabs invading Georgetown on their way inland. Young crabs were still present near the
settlement in May 1963, when Arthur Loveridge collected juveniles with carapace length 3.5mm.
It seems significant that1963 was an El Nino year, with substantial rain in some parts of the
lowlands in January and quite exceptional falls in March. Spawning landcrabs were also seen on
beaches by residents in late January 1987.
It is likely that on Ascension seaward spawning migration by the adults mainly in years
with high autumn rainfall, and the tiny offspring survive only in the rare years-normally
associated with El Nino-when cloudy and damp conditions persist for several months. The
achievements of the young are impressive: we found a crab only 12mm long near a cave north of
Sisters Peak in 1990, which had already climbed some 185m from sea level.
Gecarcinus lagostoma also occurs on Fernando de Noronha, Atol das Rocas and Trindade,
all down-current from Ascension and conceivably colonised from it. A closely related species
occurs in West Africa and other species in the Caribbean and Indo-Pacific. Assuming that
landcrab larvae can drift in ocean currents, a possible scenario for the origin of the South Atlantic
island populations would be colonisation of Ascension from the w estern coasts of Africa, and of
the Brazilian islands from Ascension. St Helena, though further north than Trindade, is
surrounded by much cooler water flowing from the south; it may never have been reached by
landcrab larvae.
History of Ascension Island