Tijdschrift voor Entomologie 160 (2017) 61–74
Diopsis mayae sp. n. (Diptera, Diopsidae), a dominant stalk-eyed fly, occurring from South Africa to Saudi Arabia Hans R. Feijen & Cobi Feijen
Diopsis mayae sp. n. is the sister species of the well-known West-African D. apicalis. It occurs from Egypt and Saudi Arabia down through eastern Africa to Namibia and South Africa. Both species belong to the D. apicalis species group, a relatively young branch of the Diopsidae, and separated at least 280,000 years ago. Although around 40 species still need to be described in the D. apicalis species group, D. mayae sp. n. and D. apicalis are by far the most dominant species in the group, while both species belong to the very small group of Afrotropical Diopsidae with a wide distribution. Data are presented on sexual dimorphism with respect to eye span for the new species and compared with those for D. apicalis. Both species are secondary stem- borers in rice and other Poaceae. Ecological information is presented for D. mayae sp. n. and compared with the information available for D. apicalis. Keywords: Diptera; Diopsidae; new species; eastern Africa; Saudi Arabia Hans R. Feijen*, Naturalis Biodiversity Center, P. O. Box 9517, 2300 RA Leiden, The Netherlands. [email protected] Cobi Feijen, Naturalis Biodiversity Center, P. O. Box 9517, 2300 RA Leiden, The Netherlands
Introduction together form a monophyletic group (Frida A.A. The genus Diopsis Linnaeus was provisionally divid- Feijen, pers. comm.). The D. indica species group is ed into a number of species groups by Feijen & Feij not directly related to the other three groups, how- en (2009). Within these species groups, four groups ever. Although the D. indica group appears morpho- are characterized by a large apical wing spot. These logically superficially close to the other three groups, four groups were briefly reviewed by Feijen & Feijen there are also crucial differences. Species of the first (2012) and include: three groups all have surstyli that are seamlessly fused to the epandrium, while in the D. indica group the surstyli are articulate. Species of the first three groups • Diopsis apicalis species group; are sexually dimorphic in relation to eye span, while • Diopsis atricapilla species group; species of the group are homomorphic in • Diopsis cruciata species group; D. indica this respect. Molecular analysis (F.A.A. Feijen, pers. • Diopsis indica species group. comm.) indicates that the D. atricapilla group and the D. cruciata group are both probably monophy- The first three groups are Afrotropical, while the last letic and closely related. In species of both groups group occurs in the Oriental region. Preliminary mo- cross-like pollinosity (= pruinescence) patterns lecular analysis indicates that the first three groups frequently occur. As was already indicated before
Tijdschrift voor Entomologie 160: 61–74, Tables 1–2, Figs 1–23. [ISSN 0040-7496]. brill.com/tve © Nederlandse Entomologische Vereniging. Published by Koninklijke Brill NV, Leiden. Published 15 December 2017. DOI 10.1163/22119434-00002064 *Corresponding author Downloaded from Brill.com10/02/2021 04:26:13PM via free access
(Feijen & Feijen 2009, 2012), the D. apicalis species diopsid: Diopsis mayae sp. n. Weekly samples of group is likely to be polyphyletic, but is still tempo- diopsid flies were collected by sweeping in the rice rarily maintained for practical reasons. To this group fields. Flies were identified, sexed and examined for belong about 40 species, but only three are currently presence of eggs and parasites (Laboulbeniales). Rice recognized: Diopsis apicalis Dalman, Diopsis lindneri hills were examined for diopsid eggs and the eggs Feijen and Diopsis longicornis Macquart. The first collected were incubated in the laboratory to deter- two species are both West-African species, while mine rates of emergence of larvae and of parasitoids D. longicornis is an abundant rice stem-boring spe- (Trichogrammatidae). Samples of rice hills were cut cies occurring in most of Sub-Saharan Africa. up to examine for diopsid larvae and pupae. The lat- In West Africa, D. apicalis is one of the most ter were also incubated to determine rate of fly emer- dominant diopsids. In a large number of papers and gence and rate of parasitism (Eulophidae). Outside museum collections Diopsis specimens from eastern the rice-growing season Diopsidae were collected and southern Africa, Egypt and the Arabian Penin- weekly in suitable locations (along rivers and other sula have been identified asD. apicalis. However, ex- wet places) surrounding the paddy fields. These were amination of large series of museum specimens from again examined. A small part of the tens of thou- all countries concerned made clear that D. apicalis sands of flies collected was pinned, while a substan- is a purely West-African species. It occurs in Benin, tial part was kept in alcohol. Burkina Faso, Cameroon, Chad, Gambia, Ghana, For the system of taking measurements, please Gabon, Guinea, Guinea-Bissau, Ivory Coast, Libe- refer to Feijen & Feijen (2011, 2013). For morpho- ria, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra logical terminology, the system proposed by Cum- Leone and Togo. In a large region extending from ming & Wood (2009) is broadly followed, while for Egypt and Saudi Arabia down through eastern Africa the wing morphology we adopted the new system to to Namibia and South Africa, D. apicalis is replaced be used in the forthcoming Manual of Afrotropical by an undescribed sister species, Diopsis mayae sp. Diptera (cf. Wootton & Ennos 1989, Saigusa 2006). n. This species had often been misidentified as For the rate of dimorphism (D), the difference be- D. apicalis. In their respective areas both species are tween males and females in allometric slope of the very dominant species. As D. mayae sp. n. is so abun- eye span vs. body length is used: a brief review is dant and has often, as D. apicalis, been indicated as given by Feijen & Feijen (2009). The following ab- being of agricultural importance, it is considered breviations are applied in the text: D – rate of di- necessary to describe it ahead of a later revision of morphism, IVS – inner vertical seta, OVS – outer the whole species group. To illustrate the dominance vertical seta, SE – standard error. of D. mayae sp. n., an example can be given for Ma- lawi. From 1971–1975, flies of the D. apicalis species group were collected and examined. These specimens Museum codens used belonged to seven undescribed species (not consider- ing Diopsis longicornis), but D. mayae sp. n. on its BMNH The Natural History Museum [formerly British own accounted for 98.0% (n = 11,398) of the total. Museum (Natural History)], London, United sp. n. is described here. The differ- Kingdom Diopsis mayae FBUB Universität Bielefeld, Bielefeld, Germany ential characters with D. apicalis will be indicated, MRAC Musée Royal de l’Afrique Centrale, Tervuren, as this is the only described species in the D. apicalis Belgium species group with which it can be confused. D. api- RMNH Naturalis Biodiversity Center (formerly calis was redescribed by Feijen (1987). The other two Rijksmuseum van Natuurlijke Historie), Leiden, The Netherlands species – D. longicornis and D. lindneri – presently ZSM Zoologische Staatssammlung des Bayerischen recognized in the group are quite different (see Feijen Staates, München, Germany & Feijen 2012). A brief outline will be presented of the ecology of D. mayae sp. n. Data are presented on sexual dimorphism with respect to eye span for D. Taxonomy mayae sp. n. and D. apicalis. Family Diopsidae Billberg, 1820 Diopsidae: Billberg, 1820: 115 (as Natio Diopsides). Type genus: Diopsis Linnaeus, 1775: 5. Material and methods In Malawi (1971–1975), Mozambique (1976– Genus Diopsis Linnaeus, 1775 1982) and Zanzibar (1982–1988) applied research Diopsis Linnaeus, 1775: 5. Type species: Diopsis ich- was carried out on rice stem-boring Diopsidae. This neumonea Linnaeus, 1775: 5, by monotypy. research concentrated on Diopsis longicornis, which was by far the most common rice diopsid, but data Diopsis mayae sp. n. were also collected on the secondmost common Figs 1, 2, 4, 6, 8, 10–18, 20, 21, 23 Downloaded from Brill.com10/02/2021 04:26:13PM via free access
35°32’33”E, 645 m, 28.viii.1974; 1♀, Limbe, Maone estate, 15°47’39”S 35°4’23”E, 1193 m, 29.iv.1971; 1♂, Limbe, Maone estate, 16.xii.1971; 1♀, Limbe, Maone estate, 19.iii.1972; 2♂, Li- longwe, Bunda College, 14°10’53”S 33°46’43”E, 1180 m, 30.iii.1972; 3♀, 3♂, Bwanji river, 14°20’S 34°44’E, 486 m, 30.x.1973; 4♀, Diampwe river, 14°8’10”S 34°5’15”E, 1169 m, 13.xi.1973; 3♀, 3♂, Diampwe river, 9.xi.1974; 1♂, Zomba, Chancellor College, Mlunguzi river, 15°23’15”S 35°20’33”E, 864 m, 6.xii.1973; 1♀, Zomba, Mlunguzi estate, 15°22’34”S 35°20’12”E, 940 m, 4.v.1975; 1♀, Zomba, Mponda stream, 15°23’20”S 35°20’3”E, 922 m, 27.v.1975; 1♂, Nkhota Kota, Chan koma bridge, 12°57’19”S 34°17’43”E, 480 m, 21.viii.1974; 1♀, Mpheta, Songani river,15°11’59”S 35°30’59”E, 630 m, 10.ix.1974; 1♂, Makoka dam, 15°32’S 35°11’E, 1029 m, 17.vi.1975; 2♀, 2♂, Mulanje, Fort Lister, 15°48’50”S 35°39’17”E, 783 m, 5.viii.1975; Mozambique, 4♀, 1♂, Moam- ba, 25°34’37”S 32°14’35”E, 104 m, 27.xi.1976; 1♀, Maputo, Botanical Garden, 25°58’18.00”S 32°34’23.87”E, 18 m, 8.vi.1977; 1♀, 1♂, Maputo, Botanical Garden, 24.vii.1977; 1♀, 2♂, Maputo, Fig. 1. Diopsis mayae sp. n. ♂, South Africa, Kwa Botanical Garden, 3.ix.1977; 3♀, 1♂, Namaacha, Mhlanga, 25°21’1’’S 28°45’28’’E, 19.iv.2014. Photo- Cascata, 25°57’40.78”S 32°2’12.90”E, 370 m, graph Peter Webb. 26.vi.1977; 16♀, 4♂, Namaacha, Cascata, 4.ix.1977; 1♀, 2♂, Namaacha, Cascata, 1.v.1980; 5♀, 5♂, Namaacha, Cascata, 28.vii.1980; 1♀, 1♂, Namaa- Misidentifications. Diopsis mayae sp. n. has often cha, Cascata, 27.ix.1981; 1♂, Buzi, açucareira, been misidentified asD. apicalis, which only occurs 19°55’2”S 34°37’36”E, 6 m, 27.x.1977; Tanzania, in West Africa (Feijen 1987). As such, records of D. 1♂, Zanzibar, Kinyasini, 5°58’20”S 39°19’4”E, 50 m, apicalis for southern and eastern Africa up to Egypt 15.v.1980, leg. G.G.M. Schulten; 2♀, Zanzibar, and Saudi Arabia are not correct. As quite a number Kizimbani, 6°5’26”S 39°15’35”E, 80 m, v.1980, of other, relatively rare Diopsis of the apicalis spe- leg. G.G.M. Schulten; 1♂, Unguja, Kizimbani, cies group occur in a broad area of eastern Africa, viii.1984; 5♀, 3♂, Unguja, Kizimbani, maize field, it can often not be ascertained which species was ix.1984; 1♂, Unguja, Kizimbani,, v.1986; 1♀, involved in the misidentification. However, based Unguja, Cheju rice, 6°13’0”S 39°23’0”E, 23 m, on sheer numbers, often D. mayae sp. n. will have 22.i.1983; 3♀, 5♂, Unguja, Mazizini, 6°12’10”S been involved. A list of publications in which the 39°12’27”E, 16 m, 23.i.1983; 1♀, 2♂, Unguja, misidentification asD. apicalis can with certainty be Mazizini, 14.ii.1983; 11♀, Unguja, Mazizini, allocated to D. mayae sp. n. includes: Sharp (1901), 6.iv.1983; 2♀, 7♂, Unguja, Southern Region, Mally (1920), Kotrba (1996), Hilger (1999), Meier 6°24’47”S 39°31’8”E, 25.i.1983; 1♀, 2♂, Pemba, & Hilger (2000), Baker et al. (2001), Meier & Baker Chake Chake, 5°14’59.29”S 39°46’45.79”E, 30 m, (2002), Kotrba & Balke (2006), Dawah & Abdul- 18.v.1980, leg. G.G.M. Schulten; 3♂, Arusha, river- lah (2008), Kotrba et al. (2010), El-Hawagry et al. bank, 3°22’22”S 36°41’45”E, 1401 m, 4.vii.1987. (2013, 2016) and Ebrahim (2009). Additional specimens examined. In connection with Type material. Holotype ♂ (RMNH), Malawi, Ka- applied research thousands of specimens more were sungu National Park, Lifupa, 13°3’24”S 33°9’26”E, examined in Malawi, Mozambique and Tanzania 1014 m, 12.iv.1975, leg. Maya D. Feijen. Paratypes from 1971–1988 and partly preserved in alcohol (all RMNH, leg. H. R. Feijen, unless indicated oth- (RMNH). In addition, identification of specimens erwise – coordinates and altitude listed only once of D. mayae sp. n. was confirmed for the following per location), Malawi, 1♀, Kasungu National Park, countries and locations: Angola, Quitondo, distr. Lifupa, 10.xi.1974; 2♂, Lake Chilwa, Likangala Rice Calulo; Botswana, Kwai river, 80 mi N of Maun; Scheme, 15°25’49”S 35°33’24”E, 637 m, 21.iv.1971; Tsotsoroga Pan; Central African Republic, Bam- 2♀, Lake Chilwa, Likangala Rice Scheme, 1.xii.1971; bari; DR Congo, Lukolela; Albertville; Boma; Ka- 2♀, 6♂, Lake Chilwa, Likangala river, 15°25’57”S tanga, Chifumanzi; Elizabethville, Lubumbashi; Downloaded from Brill.com10/02/2021 04:26:13PM via free access
Figs 2–5. Anterior view of central head (2, 3), dorsal view of thorax (4, 5). – 2, Diopsis mayae sp. n. ♂, Malawi, Lake, Chilwa, Likangala, 28.viii.1974; 3, D. apicalis ♂, Cameroon, Maya, Bassolje, 7.v.2006; 4, D. mayae sp. n. ♂, South Africa, Pietermaritzburg, 1.xii.1994; 5, D. apicalis ♀, Senegal, 7.i.1945. Scale bars = 0.5 mm, photographs Cobi Feijen.
Kisenyi (Kivu), Park Nat. Albert; Mwenda, Mt Ru- Irrigation Research Stn, Kisumu, irrigated rice; wenzori; Kifumashi; Egypt, Armant, near Luxor; Kiombit Hill Embu; Nyeri; Malawi, Muona, Ruo Ethiopia, Bahir Dar; Bahir-Dakr; Kenya, Mbita district; Mozambique, East of Mt Mulanje; Port Point, near Lake Victoria; Mombassa; Isiolo, Buffalo Amalia; Sofala; Gorongosa; Vila Pery, Cabeça do Vel- Springs Game Res.; Naro Moru River Lodge; Ahero ho; Namibia, Caprivi Mahango GR; Ovamboland Downloaded from Brill.com10/02/2021 04:26:13PM via free access
Figs 6–9. Anterior view of head (6, 7), dorsal view of wing (8,9). – 6, Diopsis mayae sp. n. ♂, Malawi, Lake Chilwa, Likangala, 28.viii.1974; 7, D. apicalis ♂, Cameroon, Maya, Bassolje, 7.v.2006; 8, D. mayae sp. n. ♂, Malawi, Diampwe riv., 20.x.1974; 9, D. apicalis ♂, Togo, Mango, 8.iv.1976. Scale bars = 1 mm, photographs Cobi Feijen.
Oshikango; Saudi Arabia, Asir, Jaheri; Asir, Wadi Mbabane, Matenga Falls; Malolotsa Falls (=Malo- Hali; Asir, Maraba; Albahha, De Al-Ain; Al-Mekh- lotja); Tanzania, Morogoro; Katona, Shirati, distr. wa; Dhee Ain; Jabal Shada al-A’la Nature Reserve; Mara; Kibaha; Myomba; Uganda, Fort Portal; Lake Wadi Minsah; Somalia, Mogadishu; South Africa, Katwe; Lira; Acholi; Kazinga Ferry; Yemen, Muke- Kwazulu-Natal, junction of Blaauw Krantz & Tugela ras; Wadi Lejij, Jebel Jihaf; Wadi Dareija; Usaifira, river; Kwazulu-Natal, Malvern; Port Natal; Kwazulu- 1 mile n. of Ta’izz; Wadi Jaira, tributary of Wadi Natal, Weenen; Kwazulu-Natal, Kloof; Kwazulu-Na- Siham; Zambia, Ndola distr., Alala Plateau; Upper tal, Pietermaritzburg, Montrose; Eshowe, Zululand; Luangwa river, junction of Luwumbu & Mwailesi Zuurberg; Durban; Grahamstown; New Hannover; river; Mazabuka; Victoria Falls; Lunzua river; Chi- East London; Transvaal, Duivelskloof; Transvaal, 10 langa; Zimbabwe, Umgusan; Harare; Mazoe; Loma- mi N. Mooketsi; N. Transvaal, Zoutpansberg, Louis gundi; Mazandellas; Bulawayo, Matopos; Bulawayo, Trichard; Gulu River mouth, Kidd’s beach; Kwa- Siloswe Matopos; Umtali; Belingwe, Mt Butwa foot- zulu-Natal, Noodsberg; Cape Province, Blauberg; hills; Khami Ruins Matabeleland; Sanyati river. South Sudan, Bhar el Ghazal; Bhar el Zeraf; Swazi- Diagnosis. Diopsis mayae sp. n. belongs to the land, Usutu forest; Bhunya, Lusuftu river; Mbabane; D. apicalis species group of the genus (see Feijen Downloaded from Brill.com10/02/2021 04:26:13PM via free access
Figs 10–14. Diopsis mayae sp. n. ♀, Malawi, Lake Chilwa, Likangala, 1973. – 10, ventral view of distal section of abdomen; 11, dorsal view of terga 8 & 10 and cerci; 12, sclerotized ring of ventral vagina wall; 13, subanal plate; 14, spermathecae. Scale bars = 0.1 mm.
2012) and can be recognized by its medium to large spines/scutellum 3.19 ± 0.04 (n = 38), ratio scutel- size, very moderate hairiness, strong facial teeth, lar spine/body length 0.22 ± 0.00 (n = 38), rounded small spine-like IVS (0.6 times stalk diameter), small apical wing spot, three clear spots between apical spine-like OVS (1.4 times stalk diameter), glossy wing spot and central infuscation, central infusca- black scutum with key pollinosity pattern (anteriorly tion darkest around crossveins and vein R4+5, femur a mesal triangle, lateral patch between humeral calli 1 slender in ♀ and ♂, ratio length/width in ♀ 5.7 and and intrascutal suture extending as a band in front in ♂ 5.9, femur 1 with on average around 23 tuber- of intrascutal sutures, posteriorly a band in front of cles in both sexes, abdomen glossy brown, ♀ sternum scutellum), black pollinose scutellum, ratio scutellar 7 consisting of two elongate sclerites, ♂ left spiracle Downloaded from Brill.com10/02/2021 04:26:13PM via free access
Figs 15–19. Diopsis mayae sp. n. ♂, Malawi, Lake Chilwa, Likangala, 1973. – 15, posterior view of epandrium with surstyli and cerci; 16, lateral view of phallapodeme; 17, ejaculatory apodeme and sac; 18, posterolateral view of surstylus. Diopsis apicalis ♂, Ivory Coast. – 19, posterolateral view of surstylus. Scale bars = 0.1 mm.
7 in membrane, surstyli rounded in posterolateral length of scutellar spine ♀ 1.46 mm ± 0.03 (range view, constricted on medial location of fusion with 1.30–1.70, n = 19), ♂ 1.41 mm ± 0.02 (range 1.25– epandrium, surstyli with less than 20% coverage 1.59, n = 19). See also Table 1. with microtrichia on outer side, ♂ sternum 6 con- sisting of two tiny sclerites, low sexual dimorphism in eye span (D = 0.78), average ratio eye span/body Description length 1.04 in ♀ and 1.23 in ♂, ratio width/length Head. Central part glossy brown, ocellar tubercle of central head 0.97. black; frons (Fig. 2) smooth with laterally very vague Distribution. Diopsis mayae sp. n. is a widespread, ridges; arcuate groove blackish with rough surface; very common species, occurring from southern Af- face glossy brown with very vague horizontal ridges; rica (including Angola and Namibia) via the eastern very large facial teeth (Fig. 2); ratio width (just below half of Africa to Egypt, Yemen and Saudi Arabia. arcuate groove)/length (ocellar tubercle to medial Measurements. Overall length ♀ 6.5 mm ± SE 0.1 edge) of central head 0.97 ± 0.01, n = 10; eye span (range 5.2–7.6, n = 50), ♂ 6.4 mm ± 0.1 (range medium-sized in female (ratio eye span/length of 4.9–8.4, n = 50); eye span ♀ 6.8 mm ± 0.1 (range body 1.04 ± SE 0.01, n = 50) and large in male (ratio 4.9–8.4, n = 50), ♂ 7.9 mm ± 0.1 (range 5.7–9.3, n eye span/length of body 1.23 ± 0.01, n = 50), rate = 50); wing length ♀ 5.6 mm ± 0.1 (range 4.8–6.3, of dimorphism low, D = 0.78 (Fig. 23, Table 1); eye n = 19), ♂ 5.3 mm ± 0.1 (range 4.6–6.1, n = 19); stalks brown and very thinly pollinose, broad apical Downloaded from Brill.com10/02/2021 04:26:13PM via free access
Table 1. Mean trait size for eye span, body length, wing and scutellar spine in mm (± SE) for Diopsis apicalis and D. mayae sp. n. Allometric slope (± SE) is the least-squares regression slope of eye span on body length. The dimor- phism column gives the difference between male allometry and female allometry. N refers to the number of pairs determining the allometric slope.
Diopsis Sex N Eye span Body length Wing Scutellar spine Allometric slope Dimorphism apicalis ♀ 20 6.6 ± 0.1 6.6 ± 0.1 5.2 ± 0.1 1.52 ± 0.02 1.14 ± 0.09 1.16 ♂ 20 7.9 ± 0.2 6.6 ± 0.1 5.1 ± 0.1 1.53 ± 0.03 2.29 ± 0.11 mayae sp. n. ♀ 50 6.8 ± 0.1 6.5 ± 0.1 5.6 ± 0.1 1.46 ± 0.03 1.47 ± 0.05 0.78 ♂ 50 7.9 ± 0.1 6.4 ± 0.1 5.3 ± 0.1 1.41 ± 0.02 2.25 ± 0.06
Figs 20–21. Diopsis mayae sp. n. hatched pupa, Malawi, Lake Chilwa, Likangala, 1973. – 20, dorsal view of pu- parium; 21, detail of anterior section with anterior spiracular stalks and larval head skeleton. Scale bars = 1 mm, photographs Cobi Feijen.
sections black, pollinose; eyes dark reddish brown; large lateral patches between humeral calli and in- IVS tiny and spine-like, 0.6 times the diameter of trascutal sutures extending in mesal direction as a the eye stalk, base of IVS hardly protruding (Fig. 6); band in front of intrascutal sutures, posteriorly a OVS medium-sized and spine-like, 1.4 times the di- band in front of scutellum, vertical sections later- ameter of the stalk; central head well covered with ally of scutellum also pollinose; scutellum black, long white setulae (Fig. 2), near antennae and eyes pollinose (in young flies and in alcohol specimens small black setulae. the scutellum can appear brownish), scutellar spines Thorax. Collar glossy black, posterior edge with glossy, pale brown on basal half, turning blackish tiny bit of pollinosity near central knob, lateral apically; pleura black, pollinose, with large central edges pollinose, scutum glossy black (Figs 1, 4) with glossy spot on posterior section of anepisternum pollinosity pattern, anteriorly a mesal triangular and dorsoposterior part of katepisternum; postscu- patch sometimes somewhat extending posteriorly, tellum black, pollinose; metapleural spines large, Downloaded from Brill.com10/02/2021 04:26:13PM via free access
Figs 22–23. Eye span plotted against body length. – 22, Diopsis apicalis; 23, D. mayae sp. n. posterolaterally directed; scutellum rectangular, Legs. Front leg with brown coxa, trochanter and fe- slightly tapering posteriorly, dorsally somewhat bul- mur and dark brown to blackish tibia and tarsi, ven- bous (Figs 1, 4), scutellar spines straight, diverging tral surface of tibia clothed in dense orange-brown under an angle of 70°, ratio scutellar spines/scutel- short setulae; mid leg uniformly brown; hind leg lum 3.19 ± 0.04 (n = 38, ♀ and ♂), ratio scutellar brown with dark brown tibia; femur 1 slender in spine/body length 0.22 ± 0.00 (n = 38, ♀ and ♂), both ♀ and ♂, ratio of length/width in ♀ 5.7 ± SE scutum without setulae, scutellum and scutellar 0.1 (n = 20) and in ♂ 5.9 ± 0.1 (n = 20), two rows of spines with a number of whitish setulae. tubercles on distal third, inner row ♀ with 12.5 ± 0.2 Wing. Large, well-rounded, apical wing spot (Fig. 8) tubercles (range 10–15, n = 37) and ♂ with 12.4 ± in cells r2+3, r4+5 and m1, extending proximally 1.4 0.3 tubercles (range 9–17, n = 37), outer row ♀ with times as far in cell r4+5 as in cell r2+3, not reaching 10.6 ± 0.2 tubercles (range 8–13, n = 37) and ♂ with posterior margin in cell m1, spot at widest part about 10.2 ± 0.2 tubercles (range 7–12, n = 37); femora 2 14% of length of wing; between apical wing spot and and 3 with distinct apical spur; all legs with sparse central infuscation a band of three clear spots sepa- white setulae. rated by infuscation along veins R4+5 and M1, clear Preabdomen. Moderately clavate; syntergum 1 + 2 + spot in cell r2+3 small (not extending beyond apex of 3 glossy brown, basally slightly darker with some pol- R2+3), clear spot in cell r4+5 more than twice as long linosity, especially medially, no sutures visible; other as the one in cell r2+3, clear spot in cell m1 occupying terga glossy brown; terga laterally with rows of fine most of the cell; central infuscation extensive, dark- white setulae; ventral preabdomen yellowish brown est around crossveins and R2+3, extending vaguely and thinly pollinose, sternum 1 darker brown, more into cell r1, extending posteriorly in cell bm+dm, glossy and more sclerotized; sterna 4 and 5 single apical half of cell cua and well into cell m4; clothed in rectangular plates. microtrichia, except for glabrous basal ar eas, which Female postabdomen. Straight, not deflexed; terga 6 include most of cell c, basal tip of cell r1, basal half and 7 single rectangular sclerites, tergum 8 repre- of cell br, basal half of “cell” bm and basal half of cell sented by two medially acute sclerites (Figs 10, 11); cua (Fig. 8). tergum 10 with one pair of long setulae and about Downloaded from Brill.com10/02/2021 04:26:13PM via free access
Table 2. Main differential character states for Diopsis apicalis and D. mayae sp. n. For ratios and allometric slopes the standard error is given (± SE).
Character D. apicalis D. mayae sp. n. Central head: ratio width (just below arcuate 1.16 ± 0.02, n = 10 0.97 ± 0.01, n = 10 groove)/length (ocellar tubercle to medial edge) Allometric slope for ♀♀ 1.14 ± 0.09, n = 20 1.47 ± 0.05, n = 50 (eye span/length of body) Rate of dimorphism D 1.16 0.78 Pollinosity in front of scutoscutellar suture Small lateral patch, with medially directed Broad band anteriorly of whole edge running almost parallel to body axis, suture Female sternum 7 Single V-shaped sclerite Two elongate sclerites Surstylus in posterior and posterolateral view Lateral edges smoothly continuing after Clearly constricted near seamless fusion with epandrium seamless fusion with epandrium Posterolateral side of surstylus Almost 50% covered with microtrichia Less than 20% covered with microtrichia Average ratio length/width femur 1 4.9 ± 0.0 in ♀, n = 20 5.7 ± 0.1 in ♀, n = 20 5.0 ± 0.0 in ♂, n = 20 5.9 ± 0.1 in ♂, n = 20 Ratio anterior spiracular stalk/posterior ~2 ~4 spiracular stalk of puparium Distribution West Africa Southern Africa, eastern Africa up to Egypt and Saudi Arabia
‘body length’ the covariate. The model was tested for In for instance two closely related species in the males and females separately. For females, the sig- Madagascar genus Eurydiopsis S. & V. (nec Frey – see nificant interaction term between species and body Feijen 1989) and two species of the D. absens spe- length (F = 4.589; p = 0.0359) indicates that females cies group, we found that the female allometric lines of D. apicalis and D. mayae have a significantly dif- were almost identical while for the males the slopes ferent slope. The similar model for the males showed remained identical but the intercepts changed. The no significant interaction term F( = 0.004; p = 0.95). two Madagascar species had separated more than 10 Given that D. apicalis and D. mayae sp. n. are closely MA ago. Likewise, we found that in a large selection related species that separated relatively recently, the of species of the Teleopsis and Megalabops genera, difference in slope of the allometric lines of the fe- which split 15 to 26 MA ago, the allometric lines males is remarkable and warrants further study. for the females were quite similar while changes in As indication for the rate of dimorphism, the the lines for the males were much more pronounced. difference between males and females in allometric According to Baker & Wilkinson (2001) “there slope for eye span on body length is commonly used. is little evidence that males and females are evolv- Feijen & Feijen-van Soest (2014) stated that allome- ing independently with respect to mean eye span”, tric lines are highly static for both sexes of Diopsidae but Voje & Hansen (2013) stated “There was little species and are useful to confirm identification of evidence for strong correlated evolution between difficult species. In the Diopsidae, sets of allometric male and female allometric slopes”. Voje & Hansen lines can be used for morphometric characterisation also stated that “selection and adaptation of eye span of genera and species groups. Static allometries are must be complex and go beyond intrasexual selec- hard to change, but elevation is assumed to be more tion on males.” Natural selection can complicate the evolvable than slope. Voje & Hansen (2013), in a issue as is found in D. longicornis, where mean eye study on adaptive change in allometric slopes of eye span increases in young flies in the weeks after emer- span in stalk-eyed flies, stated that “Both male and gence (Feijen & Feijen-van Soest 2014). No explana- female static allometric slopes showed indications of tion can at present be given for the unusually quickly phylogenetic effects, meaning that more related spe- developed difference in allometric lines for females cies have more similar static allometries.” They also of D. apicalis and D. mayae sp. n. A possible expla- concluded that allometric lines are very stable and nation might be found in the greater importance only change very slowly. As indication of the time of eye span size in females of the D. apicalis species scale they stated that “Static allometries are evolv- group and the D. cruciata species group, where fe- able on million-year time scales” and “If it takes sev- males of most species have an eye span larger than eral million years to get rid of the majority of the the length of the body. This is not found in other ancestral effect, we do not expect stalk-eyed flies taxa of Diopsidae. The most extreme case is found with different allometries to have diverged very in D. longicornis in which the mean ratio eye span/ recently.” body length is 1.29 in females against 1.49 for males. Downloaded from Brill.com10/02/2021 04:26:13PM via free access
In, for instance, Teleopsis, this ratio never gets larger seems quite plausible that stem-boring developed as than 1.0 for females. a secondary system in which the diopsid larva was Remarks on the ecology and economic importance of saprophytically feeding on the frass (debris and/ D. mayae sp. n. Both D. apicalis and D. mayae sp. n. or excrement) of primary stem-borers. From that are typical diopsids of open country. D. mayae is one system, an evolutionary development into obligate of the very few dominant Afrotropical diopsids, oc- phytophagous primary borers like D. longicornis curring over a large area and in large numbers. In the seems likely. The secondary borer D. mayae sp. n. dry season D. mayae concentrates in humid, shady was found to attack and feed on small lepidopterous places, usually in the company of other diopsids, es- borers and larvae of D. longicornis, while conspecific pecially D. longicornis. Towards the beginning of the larvae could also be attacked. Mally (1920) found rainy season they start moving to reproduction sites D. mayae sp. n. (as “D. apicalis”) as a secondary like paddy fields, maize fields and other places with stem-borer in maize stating that “The parent flies are many grasses. Over a large period of sampling in Ma- probably attracted to maize stalks by decay induced lawi the percentage males in D. mayae sp. n. came to by the borer.” 43.9% (n = 11,172). In diopsids, sex ratios deviating For the sister-species D. apicalis, egg laying and from 1:1 can partly be explained by sampling meth- larval behaviour appear more or less similar to that ods (collecting during segregated migrations or con- for D. mayae sp. n. A difference is that D. apicalis gregations). However, consistent major deviations deposits its eggs in clusters of 2–10 eggs and never cannot be explained in this way. Feijen (1984) found singly (Descamps 1957). Deeming (1982) reared for D. longicornis field-collected in Malawi a percent- D. apicalis from wild rice, sorghum and millet. age males of 52% (n = 24,162), but flies reared from According to Descamps (1957), D. apicalis lays its pupae showed an exact 1:1 ratio. The slight aber- eggs mainly on already damaged stalks, but Scheibel- ration in sex ratio for D. mayae is likely to be due reiter (1974) states that it deposits its eggs exclusively to a higher mortality in males during the year. Des- on already damaged stems. It therefore seems quite camps (1957) found for D. apicalis (indicated with certain that both D. apicalis and D. mayae sp. n. its junior synonym D. tenuipes) a percentage of males are secondary stem-borers and that they should be in the dry season of 42%, while Vercambre (1982) removed from the list of (minor) rice pests. How- found 47 to 50%. In species of the D. apicalis species ever, the possibility that one of the more rare species group, sex ratios of 1:1 appear to be the rule. In other of the D. apicalis species group in the paddy fields diopsid taxa aberrant sex ratios have been found, see is a primary borer, cannot yet be excluded. Both Burkhardt & de la Motte (1985), Presgraves et al. Descamps and Scheibelreiter recorded the killing of (1997) and Wilkinson et al. (2003). Based on data D. longicornis larvae by D. apicalis larvae. Descamps on the occurrence of “young” flies, gravid females also described the predatory behaviour of D. apicalis and Laboulbeniales parasites, D. mayae sp. n. is larvae on lepidopterous borers and various Diptera. a distinctly univoltine species. A small part of the In Malawi, eggs of D. longicornis were mainly par- population can reproduce in a somewhat different asitized by Trichogramma kalkae Schulten & Feijen period. Descamps (1957) estimated for D. apicalis and Trichogramma pinneyi Schulten & Feijen and (as D. tenuipes) 6–8 generations in just over half a further by Trichogrammatoidea simmondsi Naga- year. However, although Descamps’ thesis remains, raja and a Paracentrobia species (Feijen & Schul- after 60 years, a unique treasure trove for ecological ten 1980). No parasitized eggs of D. mayae sp. n. information on African Diopsidae, his estimates for were found, but in the laboratory T. kalkae readily number of generations often appear doubtful. parasitized those eggs. In paddy fields in Zanzibar, In Malawi, Mozambique and Tanzania, eggs of eggs of D. mayae sp. n. were found parasitized by D. mayae sp. n. were regularly found on rice stems. T. simmondsi and T. kalkae. (Feijen 1984). Pupae Eggs were normally laid singly. The number of eggs of D. longicornis were regularly found parasitized by observed was only a small fraction of the eggs laid by Eulophidae, but no parasitoids were reared from pu- D. longicornis. Eggs were sometimes also found on pae of D. mayae sp. n. On flies of D. mayae sp. n., maize and millet. D. mayae laid the eggs invariably Laboulbeniales (Ascomycota) are often encountered, on stems that had already been attacked by other especially when they are older towards the end of the stem-borers (Lepidoptera or D. longicornis). The ple- dry season. The following species are encountered: siomorphic way of life of Diopsidae can be assumed to be saprophytic. Although nothing is known about Laboulbenia diopsis Thaxter – on legs, stalks and the way of life of flies belonging to the generaCentri - scutellar spines oncus Speiser and Teloglabrus Feijen, the more basal Rhizomyces circinalis Thaxter – on sterna 1, 2 and groups of Sphyracephalinae and the Diasemopsis external genitalia genus group are all saprophytic, while stem-boring Rhizomyces ctenophorus Thaxter – on terga 1, 2, has only been found in the more derived Diopsis. It terga 4, 5 and sterna 1, 2 Downloaded from Brill.com10/02/2021 04:26:13PM via free access
Rhizomyces nr cornutus Thaxter – on terga 1, 2, l’Agriculture, de l’Élevage et des Forêts, Section Tech- sterna 1, 2 and external genitalia nique d’Agriculture Tropicale, Bulletin Scientifique 7: Stigmatomyces diopsis Thaxter – on stalks and 1–154. legs Ebrahim, A.M., 2009. Described a new recorded family Stigmatomyces porrectus Thaxter – on wings Diopsidae of (Order Diptera) with its species Diopsis Stigmatomyces schwabianus Thaxter – on legs apicalis in Egypt. – Egyptian Academic Journal of Bio- Rhizomyces circinalis is the only Laboulbeniales logical Sciences A. Entomology 2: 135–145. known that parasitizes specifically D. apicalis and El-Hawagry, M.S., M.W. Khalil, M.R. Sharaf, H.H. Fadl & A.S. Aldawood, 2013. A preliminary study on the D. mayae sp. n. It is not known from D. longicornis. insect fauna of Al-Baha Province, Saudi Arabia, with descriptions of two new species. – ZooKeys 274: 1–88. Acknowledgements El-Hawagry, M.S., M.S. Abdel-Dayem, A.A. Elgharbawy & H.M. Dhafer, 2016. A preliminary account of the We are grateful to Peter Webb for permission to use fly fauna in Jabal Shada al-A’la Nature Reserve, Saudi the photograph of a live D. mayae sp. n. The fol- Arabia, with new records and biogeographical remarks lowing scientists made study of their collections (Diptera, Insecta). – ZooKeys 636: 107–139. possible: Eliane De Coninck, Hans-Joachim Flü- Feijen, H.R., 1984. Studies on the systematics, ecology gel, Martin Hauser, Marion Kotrba (ZSM), Ray M. and economic importance of the Diopsioinea (Dip- Miller, Walter Rossi, Gerard G.M. Schulten, Axel tera). – PhD dissertation. H.M. Oosterhuis, Leiden, Ssymank, Michael von Tschirnhaus (FBUB), Dan- The Netherlands. iel Whitmore (BMNH). Walter Rossi also helped Feijen, H.R., 1987. A revision of the Diopsidae (Diptera) with the identification of the Laboulbeniales. Work described by J.W. Dalman. – Entomologica Scandi- in Malawi was supported by a grant from WOTRO navica 17: 409–422. 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