The Neuroptera of São Tomé e Principe

ABSTRACT

Two new entomological surveys were carried out in the República Democrática de São Tomé e Principe in 2019 (earlier surveys were in 1956 and 2001). Of 16 species of Neuroptera identified, only one, a Mantispidae, appears endemic to the archipelago. Chrysopidae and Hemerobiidae account for the majority of species and individuals collected, concentrated here in plantations and anthropized environments, and known to be widely distributed in Africa and even worldwide. Unusually, the family Coniopterygidae is again absent, this time on natural terrains, confirming its earlier absence in 2001 on anthropized and plantation terrains. The findings and ecological distribution support the hypothesis that Hemerobiidae and Chrysopidae were introduced with cash crop cultivation, some of them as late as the 19^th century. Their isolation in island environments is probably too recent to have allowed speciation mechanisms to generate endemic species in São Tomé.

Keywords:
Chrysopidae; Hemerobiidae; Mantispidae; Atlantic islands; Endemic species

Background

The República Democrática de São Tomé e Principe is a volcanic archipelago with a mountainous landscape located in the Gulf of Guinea (Figure 1). The climate is equatorial with an annual average temperature of 18°C and generally humid conditions year round. Nonetheless, significant rainfall variation occurs depending on elevation, geographical location - typically 5,000 mm on the south west coast but only 1,000 mm on north eastern areas - and season, June to September being relatively drier months. The archipelago consists of two main islands150 km apart; São Tomé, with an area of 850 km², and Principe, with an area of 142 km², together with several smaller islands; Cabras, Sete Pedras, Santana and Quixiba to the east, and Rolas to the south, which is located on the Equator. The Pico de São Tomé at 2,024 m above sea level is the highest point of the archipelago. With a total area of 1,001 km, São Tomé e Principe is the smallest state of Africa.

Figure 1
Geographical location and map of the achipelago of São Tomé (courtesy of the French Ministry of Foreign Affairs, Geographical department).

The islands were uninhabited when Portuguese sailors landed in December 1470, and were subsequently colonized and populated by different groups of Africans. The total population in 2020 was 220,000, settled in a limited number of population centres along the coast because of the uninhabitability of the mountainous terrain. After the introduction first of sugar cane, coffee was introduced in 1787, and cocoa in 1822 to replace sugar cane which could no longer compete with the sugar production in Brazil. Following independence in 1975, the colonial plantation economy collapsed and was gradually replaced by family-based cultivation of smaller plots. At present, also - and importantly - 30 per cent of the total area has been classified under natural conservation zones.

Past records of Neuroptera in São Tomé

The fauna of São Tomé and Principe has been poorly investigated, especially with respect to Neuroptera.

The first record is by Kimmins (1952), who designated two specimens preserved in the British Museum and collected in 1932 on the island of São Tomé (without precise date and locality as paratypes of a new species Anopochrysa africana (currently a synonym of Apochrysa leptalea Rambur, 1842).

In June 1956, the Museum national d’Histoire naturelle in Paris conducted a survey of the islands of the Gulf of Guinea as part of an oceanographic expedition on board the Calypso, Cousteau’s well-known ship. The mission collected 2♀ Mantispidae at Traz-os-Montes on the island of São Tomé (0°16 N – 6°37 E, altitude 848 m.). Viette described them as a new species Mantispa thomensis (Viette, 1958), now known as Pseudoclimaciella thomensis (Viette), which is endemic to São Tome.

In June and July 2001, the California Academy of Sciences Gulf of Guinea Expedition, 2001 spent two months, visiting the two main islands. The Expedition’s main objective was to study the potential of Neuroptera for biological control of agricultural pests, and focused almost entirely on coffee and cocoa fields and other more intensively cultivated areas. The team collected 368 specimens belonging to 13 species of Chrysopidae and Hemerobiidae (Penny, 2005). The team also observed larval pits of Myrmeleontidae in urban areas, which they could not identify in the absence of adult specimens at the time of the survey.

Altogether 15 species of Neuroptera were known on the archipelago: Hemerobiidae (3), Chrysopidae (10), Myrmeleontidae (1), and Mantispidae (1). Seven species were found on São Tomé Island only, and 2 species on Principe alone. Six species were found on both islands. Table 1 summarizes the list of recorded species to date, including the second Mantispa species identified during the present survey.

Table 1
List of Neuroptera species collected in the Republic of São Tomé e Principe (adjusted to current nomenclature).

	Island of São Tomé	Island of Principe
Chrysopidae
Ankylopteryx tristicta Navás, 1910	-	X
Ankylopteryx sp. (pallidula group)	X	-
Apertochrysa luaboensis (Tjeder, 1966) (as Pseudomallada luaboensis (Tjeder, 1966)	X	-
Apertochrysa nubilata (Navás, 1910) (as Pseudomallada sjoestedti Van der Weele, 1910)	-	X
Apochrysa leptalea (Rambur, 1842) (partim as Anopochrysa africana Kimmins, 1952)	X	-
Borniochrysa squamosa (Tjeder, 1966)	X	-
Ceratochrysa antica (Walker, 1853)	X	X
Chrysoperla congrua (Walker, 1853)	X	X
Glenochrysa conradina (Navás, 1910)	X	-
Mallada desjardinsi (Navás, 1911) (as Pseudomallada boninensis Okamoto, 1914 )	X	X
Hemerobiidae
Hemerobius reconditus Navás, 1914	X	-
Micromus timidus Hagen, 1853	X	X
Notiobiella sp.	X	X
Mantispidae
Pseudoclimaciella apicipennis (Kolbe, 1897)	X	-
Pseudoclimaciella thomensis (Viette, 1958)	X	X
Myrmeleontidae
Myrmeleon sp (according to Penny, 2005)	X	X

Present survey

In 2019, The Centro de Investigação Agronómica e Tecnológica de São Tomé e Principe conducted two entomological surveys, assisted by Microland, an environmental NGO, as part of the project São Tomé e Principe Archipelago of Biodiversity. The first survey, in February, concentrated on the island of São Tomé. The second one in November also covered Principe and Rolas.

Both surveys concentrated on conservation areas, undisturbed environments, secondary forests, altitude spots above the limit of cultivated areas, and river banks. Light traps at night complemented daytime captures.

Four species of Neuroptera, each represented by a single specimen, were collected in 2019:

Micromus timidus Hagen, 1853 [Hemerobiidae] 1♂ and Apertochrysa luaboensis (Tjeder, 1966) [Chrysopidae] 1♀ both on the Island of São Tomé, Monte Café 0°30 N - 6°64 E, alt. 632 m., 23.10.2019, at night on bushes and low vegetation.

Pseudoclimaciella apicipennis (Kolbe, 1897) [Mantispidae] 1♂ Lagoa Amelia 0°17 N – 6°36 E, 1475 m., in the centre of the island of São Tomé, 7.2.2019, night trap.

Pseudoclimaciella thomensis (Viette, 1958) 1♀ Island of Principe, Azeitona broca, 1°66 N – 7°39 E, 29.10.2019, night trap.

Of particular interest is the first recorded finding of P. thomensis on the island of Principe, and the discovery of the presence of a well-known African Mantispidae, P. apicipennis (Kolbe, 1897), not recorded previously from the archipelago.

The total number of species of Neuroptera is thus raised to 16 species (Table 1).

Discussion

The results of the three expeditions that are summarized in this paper are not directly comparable. The California Academy (2001) expedition concentrated on plantations and anthropized environments, the 2019 expedition on conservation areas and undisturbed environments. In addition, The Paris Museum (1956) and the California Academy (2001) expeditions took place in June and July which receive low rainfall (on average 29 mm in June and 16 mm in July). The 2019 expedition took place during more rainy and humid months, with 121 mm rainfall in February and 219 mm in November on average. To arrive at a definitive composition of the Neuroptera communities on these islands would probably require year-round observation. For example, species that might have escaped attention because they reach the adult stage outside the period of the survey include at least one pit-building species of Myrmeleontidae. The sampling nevertheless probably broadly covered the seasonality and differences in climatic conditions in a country which is altogether subjected to an equatorial humid climate.

A striking feature is the absence of the family Coniopterygidae both in 2001 and in our expedition in 2019, despite an intensive search for them by the California expedition (Penny, 2005), and our search on a different terrain. This is all the stranger because six species inhabit the island of Bioko (Republic of Equatorial Guinea) (Monserrat, 1990) which is located north of Principe and close to the continental coast line (40 km). The distance from the continent, 250 km for Principe, 300 km for São Tomé, has probably been a natural barrier to the dispersal of these small-sized insects.

The validity of Pseudoclimaciella thomensis Viette (Mantispidae) was questioned. Only two females were known before the present survey, very similar to P. apicipennis. The presence of a median tubercule at the basis of the metazone of the pronotum was considered by Viette as a discriminating character that justified the description of a new species. Whether it is a discriminating character of specific importance, or the result of individual variation is still discussed. During this recent survey, two variant specimens were collected, one with a tubercule and one without tubercule on the pronotal metazone. These specimens otherwise look similar to P. apicipennis. This finding leaves even more so open the question of the validity of P. thomensis.

Another striking feature is the infrequency of endemicity of species of Neuroptera. In other insect groups, such as Lepidoptera and Coleoptera, up to 30 per cent of species in São Tomé are endemic. In another study conducted during the 2019 mission, of Reduviidae, 50 per cent of the recorded species were unique to São Tomé (Prost and Cauquil, 2020). Pseudoclimaciella thomensis (Viette), if valid, seems to be the only endemic species of Neuroptera. Not only Chrysopidae and Hemerobiidae species collected in São Tomé are all present on the African continent, but some of them have their most widespread distribution in tropical areas. Micromus timidus Hagen, 1853 and Chrysoperla congrua (Walker, 1853) for example are present in the Oriental region, the Pacific islands and South Asia.

A third feature of all the expeditions is the absence of Hemerobiidae and Chrysopidae in conservation zones and in the natural environment of the islands, with the exception of Apochrysa leptalea (Rambur, 1842) which was collected exclusively in humid forest above 1300 m. Other species inhabit anthropized and modified environments. They were collected in coffee and cocoa fields, on the margin of agricultural plots, on grassy fields typical of abandoned plantations, and in peri-urban subsistence crop gardens. To the contrary, Mantispidae were found only in natural undisturbed environments. This distribution explains the difference between the results of the California expedition which focused on agricultural zones of economic interest, and yielded a substantial number of specimens of Chrysopidae and Hemerobiidae, and other surveys such as the 2019 one which concentrated on undisturbed areas and collected few specimens.

These findings support the hypothesis that Hemerobiidae and Chrysopidae were introduced with cash crop cultivation of sugar cane, cocoa, and coffee, some of them as late as the 19^th century. They are not part of the original – or native - biodiversity, to the extent it exists. Micromus timidus Hagen, Ankylopteryx tristicta (Navás) and Ceratochrysa antica (Walker) are common in cocoa plantations all over Africa, Borniochrysa squamosa (Tjeder) and Mallada desjardinsi (Navás) are locally abundant in African agricultural fields. Apertochrysa luaboensis (Tjeder) is a peri-urban species in São Tomé. Their isolation in island environments is probably too recent to have allowed speciation mechanisms to generate endemic species in São Tomé. Whereas São Tomé e Principe is considered a hot spot for biodiversity, and rightly so for most insect families, it is not true in the case of Neuroptera

On the other hand, the presence of an endemic Mantispid which is associated with undisturbed environments indicates that the group is ancient, and was present before human settlement.

Acknowledgements

I gratefully acknowledge the assistance of Gerard Filipi, President of the NGO Microland, who made the necessary arrangements for a successful field survey, and the kind help of the responsible officers of São Tomé National Parks. Sincere thanks to Odile Frank for editing and improving the manuscript.

• Funding

  This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

References

• Kimmins, D. E., 1952. A revision of the Genera of the Apochrysinae (Fam. Chrysopidae). Ann. Mag. Nat. Hist. 12 (5), 929-944.
• Monserrat, V. J., 1990. Some brown lacewings from Equatorial Guinea (Neuropteroidea: Planipennia: Hemerobiidae). J. Afr. Zool. 104, 17-22.
• Penny, N. D., 2005. The California Academy of Sciences Gulf of Guinea Expedition (2001). IV- The Neuroptera of São Tomé and Principe islands. Proc. Calif. Acad. Sci. 56 (22), 285-293.
• Prost, A., Cauquil, C., 2020. Reduviidae de l’archipel de São Tomé-et-Principe (Hemiptera). Entomologiste 76 (3), 157-160.
• Viette, P., 1958. Mission du Museum dans les îles du Golfe de Guinée. – Entomologie : XI, Planipennia Mantispidae. Bull. Soc. Entomol. Fr. 63 (9-10), 216-218.

Edited by

Associate Editor: Renato Jose Machado

Publication Dates

• Publication in this collection
  28 Oct 2022
• Date of issue
  2022

History

• Received
  05 Aug 2022
• Accepted
  21 Sept 2022