The invertebrates of Prosperous Bay Plain, St Helena a survey by Philip and Myrtle Ashmole September – December 2003 Commissioned by the St Helena Government and financed by the Foreign and Commonwealth Office

Taxonomic groups with species of conservation significance

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4.2. Taxonomic groups with species of conservation significance

The sequence of groups considered in this section follows the conventional taxonomic sequence, which is also adopted in the Guide that forms a companion document to this report. Most of the comments here are repeated there, along with full taxonomic information. Groups not mentioned here are considered to be of little relevance to consideration of airport development.

4.2.1. Mollusca: Gastropoda – snails

The snail Nesopupa turtoni, previously known only as a fossil, was found in 2003 at Site 13, in the steep and barren ravine below the signal station near King and Queen Rocks. The discovery raises the possibility that this snail may still have significant populations in the remote northeastern fringes of St Helena. More investigation is required to establish the current range of the species, but this will not be easy in view of the precipitous nature of its apparent habitat. Airport construction will presumably remove some of the snail’s potential habitat, and this effect will be compounded if surplus material is dumped over the cliffs on the seaward side, or if an access route is constructed in the ravine below the site where it was found.

4.2.2. Pseudoscorpiones – pseudoscorpions

Only two pseudoscorpions have been found in the EAA, but they have considerable conservation significance since both are in genera endemic to St Helena. The cheliferid Sphallowithius excelsus is a very attractive (though tiny) species known only from PBP, which we found at Sites 8 and 22. It is one of two members of the endemic genus Sphallowithius (the other member is known only from Peak Gut). The olpiid Hemisolinus helenae is known only from PBP and is the sole member of its endemic genus. We did not find this species in 2003, but this may be a sign of highly restricted distribution or of seasonal unavailability. Both these rare endemic species must be considered highly vulnerable to development on PBP, but the only practicable conservation measure is rigorous control of construction activity, so that damage occurs only in places where it cannot be avoided.

4.2.3. Araneae – spiders

The spiders are one of most significant animal groups occurring on Prosperous Bay Plain, with several species at risk from airport development. The reports based on collecting by the Belgians in the late 1960s listed five species as endemic to PBP or the wider EAA, and with recent discoveries this number now stands at seven (Table 1). Nine other St Helena endemic spiders occurred on the plain and also elsewhere on the island (Table 1). Subsequent taxonomic work and our own collecting has led to alteration of the accepted taxonomic status of some of the species. Out of the five spiders thought to be endemic to the plain, one (Archaeodictyna condocta) is now known to belong to a species that is widespread outside St Helena; one (Lycosa elysae) was found by us in 2003; two (Helebiona wilma and Bonapruncinia sanctaehelenae) were not found in 2003 but were represented in the Belgians' collection by three or less individuals and so might have been missed in 2003 even if actually present in small numbers; and one (Benoitodes caheni) was apparently common in the 1960s but was not found in 2003, suggesting that it is now either extinct or much reduced in numbers on the plain. On the positive side, in 2003 we found at least two additional kinds of apparently native spiders (both lycosids, provisionally assigned to the genera Lycorma and Trochosippa) on the plain, both of which may represent species new to science.

Comparison of our data with that of the Belgians also shows that several non-native species, probably introduced during the last half century, have now become widespread on PBP and the surrounding area. These include the Brown Widow spider Latrodectus geometricus, the minute oonopid spider Opopaea concolor and the prodidomid Prodidomus rufus. It is very likely that the spread of these species (and especially the first) has had important effects on the native species, although it is impossible to be sure.

For most of the endemic species of spiders in the EAA (for instance Xeropigo tridentiger, Pellenes inexcultus, Oecobius species and Philodromus signatus) the risk of extinction as a result of airport construction is probably low, since they are generally widely distributed within the arid part of the island (Species maps 8, 7, 5). A few species are so rare and/or localised in their distribution that we still have little relevant information, but any disturbance must pose some risk to them. These include Helebiona wilma, Benoitodes caheni and Bonapruncinia sanctaehelenae

The wolf spiders (family Lycosidae) present a complex but fascinating picture, and prove to be a key element in the desert ecosystem that is most fully developed in the Central Basin of Prosperous Bay Plain. Several endemic wolf spiders were listed by the Belgians as occurring on PBP, but their key role in the ecology of the basin has only now become obvious. The Prowling Wolf Spider Hogna nefasta is endemic to PBP and the Horse Point area and is abundant in dusty and gritty habitats in the Central Basin (Species map 11). We have also found what seem to be two much smaller species, hard to distinguish from Hogna. These are probably those recorded by the Belgians as “Lycosa” elysae and “Lycosa” ringens (each on the basis of a single male specimen), and we place them in the genus Brevilabus only as a temporary measure (Species map 9).

Two other wolf spider species seem to be new to science. One is probably a species of Trochosippa. We call it the Lurking Wolf Spider since it sits at its burrow entrance waiting for passing prey. We have found it only in the Central Basin, where it is typical of unvegetated dusty or gritty areas and normally occurs in groups (Species map 10). The other apparently new species, named by us the Obscure Wolf Spider and provisionally placed in the genus Lycorma, seems rare; we have found three individuals in the Central Basin and one at Site 4 a little further to the south (Species map 12). All these spiders are nocturnal and spend the day concealed in burrows in the dusty or gritty substrate (or in the case of Brevilabus under pieces of debris).

Conservation of the wolf spiders of PBP must be a major concern in consideration of possible airport development. As burrow dwellers they can only live in places where the substrate is dusty or gritty. Such places are largely restricted to the Central Basin, although there are small areas of friable ground near our Site 4 to the south of the basin, around our Site 11 on the way to Holdfast Tom, and in some parts of Horse Point Plain. The precise requirements of the different lycosid species have not yet been worked out, but in practice Trochosippa seems to occur only in the Central Basin, while Hogna is less restricted, occurring in all the places listed. Lycorma is so rare that we are not yet clear about its distribution, and the status of the two species of Brevilabus is unknown because of the difficulty of distinguishing them in the field from the young of Hogna.

Populations of all the wolf spiders will suffer when areas with friable substrates are destroyed or compacted by vehicles. The risk of extinction is low in the case of Hogna because of its relatively wide distribution. The risk to Lycorma and the Brevilabus species is hard to evaluate but must be very significant, especially in the case of the former (Species map 12).

Trochosippa (the Lurking Wolf Spider) has a highly restricted distribution (Species map 10) and is at serious risk. If, as we expect, it proves to be endemic, its world population (in terms of adults at the season of reproductive maturity) is likely to be numbered in hundreds rather than thousands. By any standards this species must be considered severely endangered. Construction of the proposed runway (under either medium or long options) will involve filling the easternmost low part of the Central Basin. Although the currently available map (Plates 1 and 3) shows little or no actual fill within the known range of the spider, any activity of heavy plant on the floor of the Central Basin near its eastern edge would be highly deleterious to the population of this species. Since this population must anyhow be at some risk during times of exceptional flooding, it is exactly the kind of species in which population reduction by a new hazard increase significantly the risk of extinction.

The significance of the threat to Trochosippa is increased by its status as a relatively “charismatic” species. Its high visibility at night, gregarious habits and intriguing predatory behaviour combine to make it a species that is of interest to the public as well as to scientists. We therefore feel that special efforts should be made to ensure that the risk to its survival is minimized.

4.2.4. Acari – mites

Several species of mites are thought to be endemic to PBP. One of them, the oribatid Liodes lanceosetosus, was found by us near Holdfast Tom and is unlikely to be endangered by airport development. Perhaps more important are the four members of the genus Chaussieria (Prostigmata: Anystidae), all of which are apparently endemic to PBP. Like the pseudoscorpions, they are vulnerable to extensive disturbance of the Central Basin. There is also one endemic species of Bdellodes that is perhaps confined to the plain, but the situation is unclear because two other very similar species are also known from the island.

4.2.5. Chilopoda – centipedes

The geophilomorph centipede Tuoba benoiti, which is apparently endemic to PBP was found by the Belgians and by us at several sites. Soil centipedes can penetrate far into loose substrates and it is possible that the species is actually quite common in the Central Basin. The small scolopendromorph Cryptops basilewskyi proves to be more widespread than the Belgians’ records indicate, occurring in the Central Basin as well as elsewhere in the EAA. We do not think that either of these species is at risk from airport development.

4.2.6. Thysanura – bristletails

The four species of bristletails (all in the family Lepismatidae) recorded from the EAA include two endemic species. Ctenolepisma sanctaehelenae was discovered by the Belgians and found by them on PBP and in a few other dry places. During the 2003 survey it was found at many sites and is unlikely to be seriously endangered by airport construction (Species map 13). However, it is one of the invertebrates that live only under stones or larger rocks lying on the surface, and which are presumably badly affected by removal of surface rocks.

The second species (not yet formally described) was discovered during the 2003 survey. It was collected only at Sites 9 and 18, Bryan’s Rock and behind the beach at Prosperous Bay (Species map 13). Since the latter site is under threat of major disruption if the bay is used for landing heavy plant during airport construction, this species must be considered endangered. Since these thysanurans cannot be identified without specialist examination, it may be advisable to organise collection of lepismatids at a number of coastal and cliff-top sites in the northeast of the island, to determine whether the new species has a wider distribution than current data indicate.

4.2.7. Orthoptera – grasshoppers and crickets

Both of St Helena’s endemic grasshoppers occur in the EAA, but one of them – Tinaria calcarata – is more characteristic of other habitats. The second species, Primnia sanctaehelenae, appears to have its main population in the EAA but is so widespread there that it will not be endangered by airport construction.

The endemic cricket Gryllus abnormis, which is wingless, was found by the Belgians only on PBP, HPP and in the Deadwood-Flagstaff area. We collected few adult Gryllus during the 2003 survey. These have all been assigned to the commoner and non-endemic G. bimaculatus, but we are puzzled by the large variation in colour that they show and wonder whether some hybridisation with G. abnormis may be occurring. It therefore seems important to search for the endemic species both on PBP and in the other places where it has been found previously, to see if it still survives.

Crickets of the family Mogoplistidae, the scaly crickets, were not recorded from the island until our work in 1995, when they were found both close to the shore and in subterranean habitats. We are inclined to think that they have been overlooked in the past, though a recent introduction cannot be ruled out. Unfortunately, taxonomic study of our specimens from St Helena, and also of some from Ascension Island (where there are probably three endemic species) has not yet been completed. During the 2003 survey we found mogoplistids only in sites near the eastern coast, both above the cliffs and nearer to sea level (Species map 14). Many of these sites will be destroyed if an airport is constructed, but we feel sure that mogoplistids are widely distributed around the precipitous shoreline of St Helena and on the cliffs above, and will survive any likely disruption of their habitat.

4.2.8. Dermaptera – earwigs

Of the four species of earwigs recorded from St Helena, three have been found on the EAA. Two of the latter are probably introduced, but the third is the Giant Earwig Labidura herculeana, which is known only from the EAA but which may now be extinct. In the 1960s the Belgians found the Giant Earwig only on HPP, but it had a more extensive range in the EAA in the past. We carried out some special trapping in 2003 in an attempt to find the Giant Earwig, but without success. Philip Ashmole and Douglas Dorward found the forceps of the largest known subfossil specimen with bird bones at Prosperous Bay in 1959. This might have been washed down from Fishers Valley, but in April 1995 we found fragments of a much smaller individual on PBP near the 2003 Site 4. This latter find was in an organic deposit mixed with old guano (including petrel bones) under a rock overhang beside a rocky gully. It is significant since it demonstrates that before the eradication of the seabirds by introduced predators, the Giant Earwig lived in seabird colonies in rocky places far from conventional soils. Although it was doubtless adapted to life in the soil under the Gumwood forests, it evidently was not restricted to that habitat, as we had assumed in the past.

4.2.9. Heteroptera – heteropteran bugs

Probably because of their mobility, no endemic heteropterans are known to be entirely restricted to PBP. Furthermore, Samphire, the most important host plant for several of them, is abundant in many other dry parts of the island, so loss of some Samphire-dominated habitat on PBP should not endanger them. Overall, we consider that Heteroptera do not present particular conservation problems in relation to airport development.

A few species, however, are worthy of comment. An interesting and probably native species is the heteropteran bug Nysius ericae (family Lygaeidae). This occurs commonly on PBP, especially in litter of Saltbush Atriplex semibaccata, and is a widespread species well known as an aerial disperser. Its endemic relative Nysius sanctaehelenae probably evolved from an ancestral Nysius stock that colonised St Helena long ago. N. sanctaehelenae has been recorded from several parts of the island, and in 2003 we found it on the recently rediscovered St Helena Boxwoods near Lots Wife, and on PBP at Sites 8 and 11. It was intriguing that at these two latter sites we did not find the smaller Nysius ericae, although the latter was present at many other sites (see Species map 15).

Hirtopsallus suedae (family Miridae) is an endemic species discovered by the Belgians and placed in an endemic genus. It is widespread at low and middle levels on the island, always in association with Samphire, and probably has a very substantial population.

4.2.10. Homoptera – homopteran bugs

The homopterans are the second major group of plant-sucking insects. It appears, however, that few groups of homopterans have established themselves naturally on St Helena, and although there are a few endemic groups (including a radiation of Cicadellidae) the majority of the species now present on the island are introduced. This paucity of species adapted to local conditions is reflected in the low numbers of homopterans found in the EAA. A particularly striking fact is that there seem to be no homopterans feeding on the dominant native plant of the area, Samphire. It should be noted, however, that no endemic shrubs such as Scrubwood and St Helena Tea were present at any of our 2003 sampling sites. Our collecting elsewhere in 1995 suggested that native homopterans were numerous on Scrubwood, but rare on St Helena Tea. A few Scrubwoods and several small stands of St Helena Tea are present in the EAA and a search for homopterans and other insects on them would be worthwhile.

One homopteran, however, is worthy of comment. Balclutha saltuella (family Cicadellidae) is a small green grass-feeding bug that was found for the first time on St Helena during the 2003 survey, occurring at several sites on PBP. This is not a newly discovered endemic but a widespread species well known as a long distance disperser. Curiously, we are also responsible for adding records of this species to the list of animals known from both Ascension Island and Great Britain; the former based on specimens supplied by John Packer, and the latter on the basis of a specimen that we caught in a trap in a cave on Tresco, Isles of Scilly. The 2003 records from PBP are a useful reminder that invertebrates have reached St Helena naturally from time to time and probably continue to do so, although the dominant mode of immigration is now with the inadvertent assistance of people.

4.2.11. Psocoptera – psocids

Only three species of psocids have previously been found in the EAA, none of them endemic. However, the 2003 survey has shown that the psocid fauna of the EAA is considerably richer than this. The samples are being studied by Dr Charles Lienhard in Geneva, but he has so far only been able to make a preliminary examination. There are probably ten species, of which one apparently represents a new endemic genus, while others are new to the island; some may be endemic. The increase in knowledge probably results mainly from the fine straining of samples from baited traps, a technique which is efficient in collecting minute invertebrates.

Several families are involved, and we comment only on those with species of conservation interest. The Liposcelididae are minute and have not yet been studied in detail, but three species are probably present in our samples. We do not yet know whether any of these are endemic. The Peripsocidae include the minute endemic species Peripsocus leleupi, discovered by the Belgians but found outside the EAA. In 2003 we found it at Site 4, ironically a site that will be destroyed if the airport is built.

The psocid of greatest interest is a member of the Trogiidae, probably representing a new endemic genus and species. It is a completely wingless, dark coloured species with a hard, shiny, black brown abdomen, and is reminiscent of a minute beetle. It will be formally described by Charles Lienhard in 2005, and was found only at Site 10 on Horse Point Plain.

4.2.12. Coleoptera – beetles

Beetles are extremely diverse in the Eastern Arid Area of St Helena, and many of the species are dry land specialists that do not occur in the more humid parts of the island. The Belgians’ reports listed five beetle species as endemic to PBP itself, and another eight endemic species that were found on the plain and also in other parts of the EAA or nearby on Flagstaff, Deadwood or in Sane Valley, but nowhere else on the island; we also include in this group one species known only from PBP and a single specimen on the Peaks.

The PBP endemics are Homoeodera scolytoides, Xestophasis xerophilus, Helenomelas basilewskyi, Tarphiophasis insulanus and T. wollastoni. The endemic species with somewhat wider distribution are Anthicodes fragilis, Homoeodera longefasciata, Aplothorax burchelli, Harpalus prosperus (also one on Peaks), Anchastus compositarum, Mellissius adumbratus, Mellissius oryctoides, and Tarphiophasis decellei.

The 13 species in these two groups deserve to be the main focus of concern over possible impact of airport construction.

Of the five PBP endemics, one that was numerous in the 1960s (Helenomelas basilewskyi) was not found during the survey in Sept-Dec 2003. Although this must raise concern about its current status, its main season is probably in the early months of the year so further search is needed at that time. Xestophasis xerophilus and Tarphiophasis wollastoni were also absent from the 2003 samples, and again it is likely that seasonal factors are involved. However, the former species was extremely localised in its distribution in the 1960s, while the latter is known from only four specimens on PBP. Further work in the autumn is desirable to check that these two species still survive. More information is also needed on the current status of Homoeodera scolytoides, of which we found only a single specimen. The fifth member of the group, Tarphiophasis insulanus, was found by the Belgians in numbers during the autumn, but it was only starting to appear when we left the island in late December 2003.

Of the endemics with slightly wider distribution, Anthicodes fragilis is not under immediate threat, except by spread of alien plants (Species map 16). Homoeodera longefasciata occurs on Samphire but also under mats of Creeper, and is not threatened. The remarkable giant carabid, Aplothorax burchelli, which may well be extinct already, had its last stronghold on Horse Point Plain and its slim chance of survival is unlikely to be significantly altered by airport development. Harpalus prosperus, a small ground beetle, is known only from two males found by the Belgians on PBP and one on the Peaks; it is probably a mobile species and although it must be considered endangered we do not think that airport development poses special risks to it. Anchastus compositarum, previously numerous on PBP and HPP, may have declined in recent decades and is a species on which more research is needed, but we do not think that airport development would have a major impact on it.

The scarabaeid Mellissius adumbratus may now be restricted to HPP and PBP (though there is a 1931 record from Deadwood) and Mellissius oryctoides is known only from a few specimens in the same areas. Neither species is likely to be much affected by airport development, provided that the Central Basin of PBP is preserved. However, we are concerned that these species may be subject to intensive predation on the larvae (and perhaps adults) by mice, and may therefore be in decline. Pseudoleichenum benoiti and the related Tarphiophasis decellei were numerous at the time of the Belgians and were found by us (Species map 17). We do not think that they are seriously at risk from airport development, although off road driving leading to ground compaction must be deleterious.

We conclude from this analysis that airport development need not have a serious impact on the endemic beetle community of PBP or the broader Eastern Arid Area. However, the continued health of this community requires rigorous restriction of development to the minimum area required for the airport and its access roads, the complete cessation of rock collecting from vulnerable areas, and control of the spread of introduced plants.

4.2.13. Hymenoptera – ants, bees and wasps

The Hymenoptera include many groups of minute parasitic wasps that are poorly known taxonomically and require specialised collecting methods. Although some of the larger species of Hymenoptera on St Helena are well known, few of the smaller ones have been identified and less than 20 endemic species have been described.

However, our work in the EAA in 2003 produced several surprises, and leads to the conclusion that the Hymenoptera of this desert area – like the spiders, beetles and other insects – comprise a substantial suite of species, largely derived from ancient colonisations, which have adapted to conditions on the plain over a long period.

A spectacular burrow-digging wasp that is common on PBP proves to be Podalonia canescens, a widespread tropical Old World member of the family Sphecidae, tribe Ammophilini. This sand wasp is mainly black, but with the front half of the abdomen and wings brilliant red-orange. It preys on caterpillars of an endemic noctuid moth, and although it has not previously been recorded from the island it is almost certainly native.

A second, stouter species of Sphecidae, black with bright orange legs and wings, was collected in the act of capturing a cricket in the Central Basin of PBP. It is a member of the tribe Larrini, another group of wasps associated with sandy places. It has not been found on St Helena in the past and may be restricted to PBP. We do not yet know whether it is endemic to St Helena, but it is undoubtedly a significant member of the desert ecosystem of the Central Basin.

Pison wollastoni is a third sphecid, known to be endemic though not restricted to the EAA. It was collected by the Belgians on HPP and PBP, as well as in other parts of the island. It is about 11 mm long and is black with fine white hairs and shiny abdomen. This species is in the subfamily Trypoxylinae, in which females provision their nests with spiders for the larvae to feed on.

Another previously known wasp is Netelia insulicola, in the family Ichneumonidae, in which the whole of the abdomen is orange red. We did not collect many specimens, but it is probably common in most parts of the EAA, parasitising caterpillars of noctuid moths. The plain is also the home of at least one other ichneumonid, probably representing a new genus in the tribe Gravenhorstiini, but we did not find this.

Smaller parasitic wasps in the family Bethylidae also live on PBP. The Belgians discovered two endemic species of Sclerodermis (restricted to PBP) and one species of Holepyris (also endemic but found at West Point as well as on PBP), all of them associated with endemic wood-eating beetles and probably parasitising their larvae. We collected some bethylids in 2003 but they have not yet been identified. Additional parasitic wasps (mainly in the family Encyrtidae) were present in our collections, but they were minute species that may well have been carried on to PBP by the wind.

4.2.14. Lepidoptera – moths

The dominant invertebrate herbivore on PBP is the endemic moth Cardepia subvelata. This is a member of the family Noctuidae, which includes the notorious cutworms and army worms that cause so much damage to agriculture. Many of these are “polyphagous”, feeding on many different kinds of plants, but we suspect that Cardepia subvelata – or at least the dry land populations of this moth – is a specialist on Samphire (Suaeda fruticosa). As such, it is probably to be found wherever there is Samphire, and is unlikely to be endangered by development. Our brief observations showed that the caterpillars of Cardepia were preyed on by the endemic lycosid spider Hogna nefasta and the sphecid wasp Podalonia canescens. We assume they were also parasitised by the common ichneumon Netelia insulicola.

The other endemic moth associated with Samphire is the geometrid Scopula separata. This has been found in various parts of the island at middle and low levels. We found the larvae, which are cryptic and apparently previously unknown, only by shaking Samphire branches, and reared the adults from them. We guess that the larvae always feed on Samphire. We do not know whether there are specialised parasitic insects exploiting this species. It should not be endangered by airport development.

The Tineidae are the most significant other group of moths on PBP and surrounding areas, and there are probably several endemic species. So far, however, we have made only a little progress in understanding them. Our collections are being studied by Keith Bland in the National Museums of Scotland in Edinburgh, but they include relatively few males (more useful taxonomically than the females, in this group) and he is not yet in a position to say how many species are present, or how many of them are already known from the island. The situation is complicated by the fact that the Belgians never published reports on the Lepidoptera that they collected. The macrolepidoptera have now been studied by Timm Karisch in Dessau, he has not yet published any results of his work on the more difficult microlepidoptera (which include the tineids). However, Robinson & Tuck (1997) have shown that St Helena has a large array of tineids in the genus Opogona, and we expect that our specimens will prove to belong in this genus.

It appears that some of the PBP tineids have reduced wings, and there is one species in which the wings are represented only by tiny flaps (see photo); this is almost certainly a new endemic species. When searching at our study sites, it was noticeable that the adult tineids were more inclined to hop or scuttle away into vegetation, than to take flight. These small scuttling tineids were especially abundant in places where there was a ground cover of Creeper Carpobrotus edulis (see also Section 5.2.6.).

4.2.15. Diptera - flies

The Belgians’ work identified only two flies of particular evolutionary and conservation interest on PBP. The most important is Atlantomyia nitida (family Tachinidae), which is the sole member of an endemic genus and is known only from PBP. It is probably a parasite of another ancient endemic, the grasshopper Primnia sanctaehelenae. Although we did not collect this fly during the work in 2003, one was probably seen at Site 12; in the same place in March 2004, Edward Thorpe collected two specimens. It is worrying that this site is close to the edge of the proposed runway and may be destroyed if it is constructed. However, we see no a priori reason why the fly should be restricted to this site, and its presumed host has a wide distribution. The fly is not easy to identify in the field and may well be present in other parts of PBP. Nonetheless, this species is of considerable conservation importance and its future welfare will need careful attention.

The second endemic fly described by the Belgians (though apparently first collected by C.R. Wallace in 1959) is Limnophora helenae (family Muscidae). It is widespread on the island and proves to be the only common muscid on PBP. Airport construction will pose no threat to this species.

Two additional possibly endemic species were found on St Helena for the first time during the 2003 survey. One is a species of Psilopa (family Ephydridae), a genus not previously recorded from the island. The specimens (one of which was collected by hand off the endemic Babies’ Toes) have been sent to a specialist in the group in the USA, but we do not yet know whether they belong to a new species. More information on the biology of the species is badly needed, since ephydrid larvae are normally aquatic. Babies’ Toes is associated with places where moisture persists for short periods after rain, or condenses, and it will be interesting to know whether the larvae live in the damp substrate or even within these succulent plants.

The second species newly recorded on the island is a species of Scenopinus (family Scenopinidae). Another species of this genus, S. glabrifrons, was found by the Belgians in many parts of the island, including PBP, but our specimens belong to a different group and are close to S. canarius, endemic to the Canary Islands. The larvae of these flies are predators, and it seems likely that the newly found species preys on larvae of the endemic tineid moths, or perhaps on beetles. The species was found at several sites in the EAA and is not likely to be endangered by airport construction.

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