Research Article |
Corresponding author: Jason G.H. Londt ( robber4afr@telkomsa.net ) Academic editor: Pavel Stoev
© 2016 Jason G.H. Londt.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Londt JGH (2016) A review of the genus Gibbasilus Londt, 1986 in southern Africa (Diptera, Asilidae). African Invertebrates 57(1): 67-81. https://doi.org/10.3897/AfrInvertebr.57.8696
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Gibbasilus Londt, 1986, a small genus of asiline Asilidae endemic to the Western Cape Province of South Africa, is taxonomically revised. Three species are described for the first time (alboala, condylus, crinitus) and added to those already known (arenaceus, brevicolis, centrolobus). A key for the identification of species is provided. Little is known of their biology, but a close association with species of Restionaceae, a dominant element of the Cape Floristic Region, has been observed. It is suspected that females, which possess long, laterally compressed, knife-like ovipositors, use these plants as oviposition sites.
Afrotropical, Asilidae , Asilinae , Gibbasilus , new species, Restionaceae
The acquisition of interesting new material representative of the distinctive South African asilid genus Gibbasilus Londt, 1986, gave rise to the need to provide a new taxonomic perspective on the genus whose history is brief and can be summarised as follows:
At the commencement of this study there were therefore only three species included in the genus. New material which has been incorporated into the KwaZulu-Natal Museum's, collection over the last 25 years allows a further three species to be described. All are to be found in a relatively small region of the Western Cape Province of South Africa.
Much of the material previously recorded by
Illustrations provided are designed to complement those of
Gibbasilus Londt, 1986: 2. Type species: Gibbasilus arenaceus Londt, 1986, by original designation and monotypy.
(modified from
L. albus – white, ala – f. wing; refers to the milky white, opaque bases to the wings.
Based on 2♂ specimens, ♀ unknown.
Head: Black, fine silver pruinose, black, pale yellow and white setose. Antenna: Black, fine silver pruinose, scape and pedicel black setose. Segmental ratios (scape as 1) = 1 : 0.6 : 1.2 : 0.7 (elements of style = 0.1, 0.5, 0.1). Style composed of three elements (small basal segment-like element, long middle rod-like element, terminal seta-like sensory element). Face black, fine dull silver pruinose, profile plane (straight, no gibbosity evident). Mystax long, well-developed, extending from epistomal margin to antennal sockets, macrosetae pale yellow along epistomal margin, otherwise all black. Frons and vertex black, dull silver pruinose, fine, long, black setose. Ocellar tubercle with long, fine, black setae. Occipital region black, silver pruinose, black setose dorsally, pale yellow laterally, fine white setose ventrally. Palpi 2-segmented, segment 1 white setose, 2 black setose. Proboscis shiny black, fine white setose.
Thorax: Dark red-brown to black, fine, dull, silver pruinose, black, pale orange, pale yellow and white setose. Pronotum black, white setose. Mesonotum black, entirely dull silver pruinose. Acrostichals numerous, mane-like, predominantly black except for few white setae anteriorly and a cluster of fine white setae posteriorly. Dorsocentrals well-developed, black, extending both anterior and posterior of transverse suture. Mesonotal macrosetae: Strong, pale orange, 2 npl, 2 spal, 1 pal. Scutellum black, entirely dull silver pruinose; disc fine white setose, 2 long, black apical scutellar macrosetae. Pleura: Dark red-brown to black, entirely dull silver pruinose, pale yellow and white setose. Katatergal setae weak, pale yellowish. Anatergites uniformly dull silver pruinose, asetose. Mediotergite weakly fine white setose medially. Legs: Coxae dark red-brown to black, fine, dull silver pruinose, fine white setose. Trochanters shiny black, apruinose, fine white setose. Femora slightly inflated, dark red-brown to black except for narrow orange distal tip, macrosetae mostly yellowish (except for 3–5 black proximoventral setae on fore femora). Tibiae mostly brown-orange becoming progressively darker distally, macrosetae mostly orange (a few black at distal tip). Tarsi dark red-brown with black and orange macrosetae. Claws dark red-brown to black, pulvilli and empodia well developed, orange. Wings (Fig.
Abdomen: Entirely dark red-brown to black, extensively dull silver pruinose, except lateral margins of T2 and T3 which are shiny apruinose. Terga fine short white setose, T1–4 with 1–2 laterally situated pale yellow macrosetae (progressively diminishing in size towards terminalia). Sterna fine, longish setose. ♂ genitalia (Figs
SOUTH AFRICA: 1♂ "S Africa: Cape #69 / 1 km W Nieuwoudtville / 31°23'S, 19°06'E 800 m / Date: 4.xi.1991 / Coll: J.G.H. Londt / Caravan Park and area" (
1♂ with identical label (
This species bears a strong resemblance to condylus sp. n., described below, but is immediately recognised by the milky white bases to the wings. This condition, although unique within Gibbasilus, is encountered in other asilid genera such as Hypenetes Loew, 1858 (
Known only from the type locality. Collected in November. The general habitat consisted of endemic fynbos plant species and large boulders.
Phenology of Gibbasilus species. Months, starting at July, abbreviated as shown.
J | A | S | O | N | D | J | F | M | A | M | J | |
---|---|---|---|---|---|---|---|---|---|---|---|---|
alboala | - | - | - | - | ● | - | - | - | - | - | - | - |
arenaceus | - | - | ● | ● | ● | - | - | - | - | - | - | - |
brevicolis | - | - | ● | - | - | - | - | - | - | - | - | - |
centrolobus | - | - | ● | - | ● | - | - | - | - | - | - | - |
condylus | - | - | - | - | ● | - | - | - | - | - | - | - |
crinitus | - | - | ● | - | ● | - | - | - | - | - | - | - |
Gibbasilus arenaceus Londt, 1986: 2. figs 1 (habitus), 2 (antenna), 3 (wing), 4–7 (♂ terminalia), 8 (♀ ovipositor), 9–12 (pupa).
The species was fully described by
SOUTH AFRICA: 1♀ paratype "South Africa, Cape Prov. / Botterkloof Pass [c.31°40'S, 19°16'E 660 m], top of / Sept. 13, 1972, 3119Cd / 2230 ft., ME&BJ Irwin / White sand dune assoc." (
This species bears a strong resemblance to crinitus sp. n., described below, but can be separated from that species on features of the male terminalia (inn particular the poorly developed pale setae found along the posterior margin of S8).
Known from six localities approximately centred on the towns of Vanrhynsdorp and Clanwilliam. Collected during the months of September, October and November. Specimens collected by me 22 km south of Vanrhynsdorp, on the road to the Gifberg, were found perching near the tops of the vertical stems of a tall unidentified plant species belonging to the family Restionaceae growing on the edge of an old ploughed field (31°46'16"S, 18°45'56"E 545 m). Although oviposition was not observed, it is probable that females use their knife-like ovipositors to insert eggs into suitable crevices found on these plants.
Gibbasilus brevicolis Londt, 1990b: 13. figs 3 (wing), 20–23 (♂ terminalia).
The species was fully described by
SOUTH AFRICA: 1♂ holotype "Pakhuis Pass [c.32°08'S, 19°02'E 635 m], C.P. S.A.M., 9:1961 [ix.1961]" (
Known only from the type locality of Pakhuis Pass, a road to the east of Clanwilliam leading to the Biedouw Valley. Collected in September. No biological information is available. The pass is rocky and dominated by indigenous fynbos.
Gibbasilus centrolobus Londt, 1990b: 15. figs 4 (wing), 24–27 (♂ terminalia).
The species was described by
SOUTH AFRICA: 1♂ holotype "Clan William [c.32°12'S, 18°54'E 165 m] / ix-1928 / Dr. Brauns" (
Distribution (Fig.
L. m. condylus - prominence; refers to the lobed S8 in males.
Based on 2♂ and 6♀.
Head: Black, silver pruinose, black, pale yellow and white setose. Antenna: Black, fine silver pruinose, scape and pedicel black setose. Segmental ratios (scape as 1) = 1 : 0.7 : 1.4 : 0.8 (style = 0.2, 0.5, 0.1). Style composed of three elements (small basal segment-like element, long middle rod-like element, terminal seta-like sensory element). Face black, fine silver pruinose, profile plane. Mystax long, well-developed, extending from epistomal margin to antennal sockets, macrosetae white along epistomal margin, otherwise black. Frons and vertex black, silver pruinose, fine, long, black setose. Ocellar tubercle with long, fine, black setae. Occipital region black, silver pruinose, black setose dorsally (may be a few orange), pale yellow laterally, fine white setose ventrally. Palpi 2-segmented, segment 1 white setose, 2 black setose. Proboscis shiny dark red-brown to black, fine white setose.
Thorax: Dark red-brown to black, fine, dull, silver pruinose, black, pale orange, pale yellow and white setose. Pronotum dark red-brown to black, white setose. Mesonotum black, entirely dull silver pruinose. Acrostichals numerous, mane-like, predominantly black except for few white setae anteriorly and a cluster of fine white setae posteriorly. Dorsocentrals well-developed, black, extending both anterior and posterior of transverse suture. Mesonotal macrosetae: Strong, orange and black, 2 npl (orange), 2 spal (black), 1 pal (black). Scutellum black, entirely silver pruinose; disc fine white setose, 2 long, black apical scutellar macrosetae. Pleura: Dark red-brown to black, entirely silver pruinose, pale yellow and white setose. Katatergal setae pale yellowish. Anatergites uniformly dull silver pruinose, asetose. Mediotergite weakly fine white setose medially. Legs: Coxae dark red-brown to black, fine, dull silver pruinose, fine white setose. Trochanters shiny black, apruinose, fine white setose. Femora slightly inflated, dark red-brown to black except for narrow orange distal tip, macrosetae mostly yellowish (except for 3–5 black proximoventral setae on fore femora). Tibiae mostly brown-orange becoming progressively darker distally, macrosetae mostly orange (a few black at distal tip). Tarsi dark red-brown with black and orange macrosetae. Claws dark red-brown to black, pulvilli and empodia well developed, brown-orange. Wings: ♂ 7.6 (7.4–7.8) × 2.6 mm, ♀ 7.6 (6.3–8.6) × 2.5 (2.1–2.9) mm. Veins brown, cells r1, m3, and cua closed and stalked, membrane unstained (wing tip may be slightly brown stained), entirely transparent and lacking microtrichia. Halter pale yellow to orange.
Abdomen: Entirely dark red-brown to black, extensively dull silver pruinose, except lateral margins of T2–5 and parts of S2–2 which are shiny apruinose. Terga fine short white setose except for narrow medial strip of fine black setae, T1–6 with 1–3 laterally situated pale yellow macrosetae (progressively diminishing in size and number towards terminalia). Sterna fine, longish setose. ♂ genitalia (Figs
SOUTH AFRICA: 1♂ "South Africa W Cape / Kagga Kamma Nat. Res. / 32°45'12"S, 019°34'23"E / J&A Londt 12.xi.2015 / 1080 m Sandy vynbos" (
4♀ "S Africa, Cape #65 / 22 km S Vanrhynsdorp / 31°46'S, 18°46'E 600 m / Date: 23.xi.1991 / Coll: J.G.H. Londt / Gifberg Edge old land" (
As mentioned earlier, this species bears a strong resemblance to alboala sp. n. (described above), but can easily be separated from that species as it has entirely transparent wing membranes, lacking the somewhat opaque, milky basal wing membranes diagnostic for alboala.
Known from four fairly widely separated localities. Collected during the months of October and November. Specimens collected by me, at three localities, were found perching near the tops of the vertical stems of a tall unidentified species belonging to the Restionaceae or sunning themselves on stones. A typical habitat at the Kagga Kamma Nature Reserve is illustrated (Fig.
L. m. crinitus – hairy; refers to the mediodistal cluster of black setae found on S8.
Based on type series consisting of 5♂ 3♀.
Head: Black, fine silver pruinose, black and white setose. Antenna: Black, fine silver pruinose, scape and pedicel black setose. Segmental ratios (scape as 1) = 1 : 0.6 : 1.5 : 0.7 (elements of style = 0.2, 0.4, 0.1). Style composed of three elements (small basal segment-like element, long middle rod-like element, terminal seta-like sensory element). Face black, silver pruinose, profile plane. Mystax long, well-developed, extending from epistomal margin to antennal sockets, macrosetae black (laterally) and white (centrally) down entire depth of face. Frons and vertex black, weakly silver pruinose, fine, long, black setose. Ocellar tubercle with long, fine, black setae. Postocular (occipital) region black, silver pruinose, mostly black setose dorsally, white laterally and ventrally. Palpi 2-segmented, segment 1 white setose, 2 black setose. Proboscis shiny black, fine white setose.
Thorax: Dark red-brown to black, silver pruinose, black, pale yellow and white setose. Pronotum dark red-brown to black, white setose. Mesonotum black, entirely fine silver pruinose. Acrostichals numerous, mane-like, predominantly black except for a few white setae anteriorly and a cluster of fine white setae posteriorly. Dorsocentrals well-developed, black, extending both anterior and posterior of transverse suture. Mesonotal macrosetae: Strong, pale yellow, 2 npl, 2 spal, 1 pal. Scutellum black, entirely dull silver pruinose; disc fine white setose, 2 long, pale yellow apical macrosetae. Pleura: Dark red-brown to black, entirely dull silver pruinose, white setose. Katatergal setae weak, white. Anatergites uniformly dull silver pruinose, asetose. Mediotergite fine white setose medially. Legs: Coxae Dark red-brown to black, fine, dull silver pruinose, fine white setose. Trochanters shiny black, apruinose, fine white setose. Femora slightly inflated, entirely dark red-brown to black, macrosetae mostly black (except for a few pale orange anterodorsally on mes- and metathoracic femora). Tibiae orange except for dark red-brown to black distal quarter, macrosetae mostly black (a few orange). Tarsi dark red-brown with black macrosetae (except for a few yellow on Tar 1). Claws dark red-brown to black, pulvilli and empodia well developed, brown. Wings: ♂ 7.2 (6.3–7.7) × 2.4 (2.1–2.6) mm, ♀ 6.6 (6.2–7.3) × 2.1 (2.1–2.2) mm. Veins dark red-brown to black, cells r1, m3, and cua closed and stalked, membrane unstained, entirely transparent except for slight opaqueness resulting from presence of microtrichia primarily distally and broadly along hind margins. Halter pale yellow to orange.
Abdomen: Entirely dark red-brown to black, extensively dull silver pruinose, weakly along lateral margins of T2–4 and S2–4 which are shiny apruinose. Terga fine short white setose except for narrow mid-dorsal strip of tiny black setae, T1–5 with 2–3 laterally situated pale yellow, weak macrosetae (progressively diminishing in size towards terminalia). Sterna fine, longish setose.
Abdomen: Entirely dark red-brown to black, extensively dull silver pruinose, except lateral margins of T2–3 which are shiny apruinose. Terga fine short white setose, T1–4 with 1–2 laterally situated pale yellow macrosetae (progressively diminishing in size towards terminalia). Sterna fine, longish setose. ♂ genitalia (Figs
SOUTH AFRICA: 1♂ "South Africa W Cape / Kagga Kamma Nat. Res. / 32°45'12"S, 019°34'23"E / J&A Londt 12.xi.2015 / 1080 m Sandy vynbos" (
SOUTH AFRICA: 2♂ 1♀ "South Africa, C.P. / Clanwilliam, 32°10'S, 18°53'E. 30.ix.1986 / M.W. Mansell & J.H. / Hoffmann", "Collected / at light" (
This species bears a strong resemblance to arenaceus, but can be separated from that species on features of the male terminalia (mainly on the well-developed black setae found along the posterior margin of S8). While crinitus sp. n. may eventually prove to be a variant of arenaceus there is presently insufficient material to verify that possibility. It should be noted that the material collected at Clanwilliam was recorded previously by
Known only from three localities. Collected in September and November. Specimens collected by me were taken resting on the stems of an unidentified species of Restionaceae or sunning themselves on rocks. The species being found sympatrically with condylus, the general habitat being illustrated in Fig.
1 | Wings microtrichose distally, and broadly along posterior margins | 2 |
– | Wings entirely lacking microtrichia | 4 |
2 | Mystax composed of black and white (or pale yellow) setae mixed down entire facial profile | 3 |
– | Mystax with white (or pale yellow) setae confined to ventral region of face around epistomal margin | centrolobus Londt, 1990 |
3 | Males with posterior margin of S8 bearing short, pale yellow setae medially | arenaceus Londt, 1986 |
– | Males with posterior margin of S8 bearing longish, black setae medially | crinitus sp. n. |
4 | Wing membrane entirely transparent | 5 |
– | Wings basally with membrane milky white, opaque | alboala sp. n. |
5 | Males with posterior margin of S8 with a well-defined distomedial projection; gonostylus long and narrow in lateral view; aedeagus highly convoluted; gonocoxite smoothly rounded distally | condylus sp. n. |
– | Males with posterior margin of S8 lacking a distomedial projection; gonostylus short and broad in lateral view; aedeagus simply bowed and not highly convoluted; gonocoxite with dorsoventrally compressed distal projection | brevicolis Londt, 1990 |
Taxonomy: With the description of three new species, Gibbasilus is now represented by six species. With the discovery that only three of these possess microtrichose wing membranes the genus can be split into two groups as demonstrated in the key. Females are now known for four species and it is of interest that all those with microtrichose wings (arenaceus, centrolobus, crinitus) possess slender ovipositors (length : depth ratios ranging from 3.64.7 – 1). G. condylus, on the other hand, has a more robust ovipositor (length : depth ratio of 2.7 : 1) which might suggest that when females of alboala and brevicolis are discovered that these too will possess fairly robust ovipositors.
Distribution and biology: Gibbasilus is confined to a rather small region of the Western Cape Province of South Africa (Fig.
The University of KwaZulu-Natal is thanked for allocating funding in support of my research, as is the National Research Foundation (NRF) of South Africa. The KwaZulu-Natal Museum continues to provide various services and Mr Burger Muller, in particular, is thanked for his significant contribution in supplying photographs and generating distribution maps. Finally, my wife, Ann, is thanked for her valuable assistance and support.