Research Article |
Jason G. H. Londt‡§
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Corresponding author: Jason G. H. Londt ( londtja@telkomsa.net ) Academic editor: Torsten Dikow
© 2020 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 (2020) A survey of grassland Asilidae (Diptera) at Jacana Eco Estate, Hilton, South Africa. African Invertebrates 61(1): 29-48. https://doi.org/10.3897/AfrInvertebr.61.50895
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Abstract
A year-long survey of grassland Asilidae was undertaken at Jacana Eco Estate, Hilton, KwaZulu-Natal, South Africa. The following 18 species of Asilidae, in alphabetical order, were encountered: Caenoura annulitarsis (Loew, 1858), Damalis monochaetes Londt, 1989, Dasophrys androclea (Walker, 1849), Dasophrys fortis Londt, 1981, Dasophrys tarsalis (Ricardo, 1920), Dasophrys umbripennis Londt, 1981, Dysclytus firmatus (Walker, 1857), Euscelidia vallis Dikow, 2003, Ischiolobos mesotopos Londt, 2005, Leptogaster sp., Melouromyia natalensis (Ricardo, 1919), Microstylum sp., Neolophonotus hirsutus (Ricardo, 1920), Neolophonotus variabilis Londt, 1986, Neolophonotus wroughtoni (Ricardo, 1920), Pegesimallus bicolor (Loew, 1858), Pegesimallus pedunculatus (Loew, 1858), Rhipidocephala obscurata Oldroyd, 1966. Their flight periods were recorded and tabulated. The variety and numbers encountered suggest that the grassland invertebrate community is healthy and that the grassland is worthy of its conservation status.
Keywords
Africa, Asilidae, Grassland, seasonal incidence, conservation
Introduction
Grassland is one of South Africa’s most neglected and threatened biomes. Human development has placed the biome at great risk of being severely compromised (
In 2018, it came to the author’s attention that a relatively small housing development was taking place in Hilton, a small village on the outskirts of Pietermaritzburg, in the midlands of KwaZulu-Natal, South Africa. The developers of what is now called the Jacana Eco Estate, the Kotze Family Trust, had been given permission to build a number of houses on Portion 25 of Erf 330 Hilton. The area, which is dominated by grassland, is currently bordered by a few houses and an area that used to be a pine plantation. The grassland had been minimally impacted by human activity and was, therefore, considered one of the better pieces of relatively unspoilt grassland in the area. An Environmental Management Plan had been compiled in 2016 by Environmental Planning Services, Glenwood, Durban and this was to be implemented throughout the development phase and subsequently by the owners of houses built on the estate and adjacent to the grassland.
Having undertaken a survey of grassland Asilidae at Queen Elizabeth Park, in Pietermaritzburg (
When approached, Mr Paul Kotze, of the Kotze Family Trust, kindly gave permission for weekly sampling of Asilidae to commence at the start of 2019. The results of this year-long survey are here presented.
Jacana Eco Estate
The Jacana Eco Estate, hereafter merely called Jacana, is situated at ca. 29°32'35"S, 30°17'38"E (Fig.
While a fairly comprehensive Biodiversity Assessment had been carried out by Dr JH Grobler in October 2007 of the ‘Bracken Ridge Development (Hilton Erf. 330) Pietermaritzburg’ (
Grasses likely to be encountered at Jacana Eco Estate as listed by Roderick Collett (alphabetically within categories), together with common names as provided by Van Oudtshoorn (1992) and definitions of categories.
| Increaser I | Alloteropsis semialata (Black-seed Grass); Digitaria tricholaenoides (Purple Finger Grass); Eulalia villosa (Golden Velvet Grass); Setaria nigrirostris (Black-seed Bristle Grass); Trachypogon spicatus (Giant Spear Grass); Tristachya leucothrix (Hairy Trident Grass) |
| Decreaser | Brachiaria serrata (Velvet Signal Grass); Diheteropogon amplectens (Broad-leaved Bluestem); Monocymbium ceresiiforme (Boat Grass); Themeda triandra (Red Grass) |
| Increaser 11a | Eragrostis capensis (Heart-seed Love Grass); Harpochloa falx (caterpillar Grass); Heteropogon contortus (Spear Grass) |
| Increaser 11b | Eragrostis curvula (Weeping Love Grass); Eragrostis plana (Tough Love Grass); Eragrostic racemosa (Narrow Heart Love Grass); Hyparrhenia hirta (Common Thatching Grass); Sporobolus africanus (Ratstail Dropseed) |
| Increaser 11c | Microchloa caffra (Pincushion Grass); Paspalum scrobiculatum (Veld Paspalum) |
| Increaser 111 | Aristida junciformis (Gongoni Three-awn); Diheteropogon filifolius (Thread-leaved Bluestem); Elionurus muticus (Wire Grass) |
In addition to the above documentation, I was given a copy of an unpublished Environmental Management Plan for Hilton Green, compiled in 2016 by Environmental Planning Services (197 Masizi Kunene Road, Glenwood, Durban), relating to Portion 25 of Erf 330, Hilton. While this document was intended to guide the developer during the building phase of Jacana, it contained no environmental information relating specifically to the proposed Eco Estate.
While undertaking the asilid survey, the grassland was burned in keeping with conventional management practices. The upper part of the lower field, below the access road, was burned at the end of August (week 35) while the lower part of this area was burned a week later, during the first week of September (week 36). The entire upper field, above the access road, was then burned in early October (week 41). Although some flowering plants, other than grasses, were encountered throughout the survey, many appeared soon after these burns. The following list of plants, photographed at Jacana, is by no means exhaustive, but is provided in order to stimulate further interest in what the Eco Estate has to offer botanically. Where known, common names, as recorded by
Materials and methods
Asilidae were sampled using a standard, hand-held, 30 cm diameter, 120 cm long entomological net. While walking, the vegetation was visually scanned (in order to spot larger, more active species) and swept with the net (in order to collect small species adapted for living within the vegetation) for an hour, one morning per week (usually on a Monday). While most of the Asilidae collected were merely identified, counted and released, a few representatives of each species were kept in order to verify identifications. Retained specimens were mounted, labelled and incorporated into the Diptera collection of the KwaZulu-Natal Museum, Pietermaritzburg, at the end of the survey.
Weather, being an important factor, was monitored, with care being taken to sample at more or less the same time of day (between 10:00 h and 14:00 h) and when the vegetation was dry. Sampling was not possible on 4 weeks of the year (weeks 4, 24, 29, 44) due to other commitments. On each occasion, a thermometer was used to record ambient temperature, which ranged from 15 °C (week 26) to 33 °C (week 41). The mean temperature for all sampling occasions was 23 °C. Figs
Care was taken to transect the entire length of the area, spending roughly the same time in the two adjacent fields on each sampling occasion. The distance covered on each occasion was approximately 1.5 km (measured with a pedometer). With the scheduled burning of the vegetation during weeks 35, 36 and 41, sweeping had to be confined to suitable vegetation and greater emphasis placed on visual sightings of ground inhabiting species until the vegetation had recovered sufficiently for more standardised sampling.
Although rainfall data was not available for the Jacana study site, Table
Results
Eighteen species of Asilidae were collected during the year-long survey at Jacana (Table
Species activity at Jacana Eco Estate throughout 2019. ■ – Abundant (> 10 specimens), ● – Common (< 10 > 2 specimens), • – Uncommon (< 3 specimens), x – No collection made. S = Summer, A = Autumn, W = Winter, SP = Spring. Species in order of appearance: 1 Euscelidia vallis 2 Ischiolobos mesotopos 3 Pegesimallus bicolor 4 Caenoura annulitarsis 5 Pegesimallus pedunculatus 6 Melouromyia natalensis Damalis monochaetes 8 Dasophrys androclea 9 Dasophrys tarsalis 10 Neolophonotus wroughtoni 11 Dasophrys umbripennis 12 Neolophonotus hirsutus 13 Neolophonotus variabilis 14 Leptogaster sp. 15 Microstylum sp. 16 Dysclytus firmatus 17 Dasophrys fortis 18 Rhipidocephala obscurata.
| Species | Week | |||||||||||||||||||||||||
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | |
| 1 | ■ | ■ | ■ | x | ■ | ■ | ■ | ■ | ■ | ■ | ■ | ● | • | • | • | – | – | – | – | – | – | – | – | x | – | – |
| 2 | ● | ■ | ■ | x | • | • | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – |
| 3 | • | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – |
| 4 | – | – | – | x | • | • | • | ● | ● | ● | ■ | ■ | ■ | ■ | ■ | • | • | ● | • | • | – | – | – | x | – | – |
| 5 | – | – | – | x | – | – | • | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – |
| 6 | – | – | – | x | – | – | • | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – |
| 7 | – | – | – | x | – | – | – | – | – | ● | ■ | ■ | ■ | ■ | ■ | ■ | ● | ● | • | – | – | – | – | x | – | – |
| 8 | – | – | – | x | – | – | – | – | – | – | • | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – |
| 9 | – | – | – | x | – | – | – | – | – | – | – | ● | ■ | ■ | ■ | ● | • | ● | – | – | • | – | – | x | – | – |
| 10 | – | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | • | • | – | x | – | – |
| 11 | – | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – |
| 12 | – | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – |
| 13 | – | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – |
| 14 | – | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – |
| 15 | – | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – |
| 16 | – | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – |
| 17 | – | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – |
| 18 | – | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – |
| Season | S | S | S | S | S | A | A | A | A | A | A | A | A | A | A | A | A | A | W | W | W | W | W | W | W | W |
| No. Sp. | 3 | 2 | 2 | x | 3 | 3 | 4 | 2 | 2 | 3 | 4 | 4 | 4 | 4 | 4 | 3 | 3 | 3 | 2 | 1 | 2 | 1 | 0 | x | 0 | 0 |
| Species | Week | |||||||||||||||||||||||||
| 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | |
| 1 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | ● | ● | x | ● | • | ● | ■ | – | – | • | ■ |
| 2 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | • | ● | ● | ● | ■ | ■ | ■ | ■ |
| 3 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – | – | – | – | – | – | – |
| 4 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – | – | – | – | – | – | – |
| 5 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – | – | – | – | – | – | – |
| 6 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – | – | – | – | – | – | – |
| 7 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – | – | – | – | – | – | – |
| 8 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – | – | – | – | – | – | – |
| 9 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – | – | – | – | – | – | – |
| 10 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – | – | – | – | – | – | – |
| 11 | – | • | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – | – | – | – | – | – | – |
| 12 | – | – | x | – | – | – | – | – | – | • | ● | ● | ● | – | – | – | – | x | – | – | – | – | – | – | – | – |
| 13 | – | – | x | – | – | – | – | – | – | • | – | – | • | – | ● | ● | ● | x | ● | • | – | – | – | – | – | • |
| 14 | – | – | x | – | – | – | – | – | – | – | – | • | – | – | – | – | – | x | – | – | – | – | – | – | – | – |
| 15 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | ■ | ■ | ■ | ■ | ● | ● | ● | • |
| 16 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | ● | ● | ● | • | – | – | – |
| 17 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – | – | – | – | – | • | – |
| 18 | – | – | x | – | – | – | – | – | – | – | – | – | – | – | – | – | – | x | – | – | – | – | – | – | • | – |
| Season | W | W | W | W | W | SP | SP | SP | SP | SP | SP | SP | SP | SP | SP | SP | SP | SP | S | S | S | S | S | S | S | S |
| No. Sp. | 0 | 1 | x | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 1 | 2 | 2 | 0 | 1 | 2 | 2 | x | 4 | 5 | 4 | 4 | 3 | 2 | 5 | 4 |
Euscelidia vallis
Remarks
This species was positively identified by Dikow (pers com) who reviewed the extensive Afrotropical Euscelidia fauna, comprising over fifty species (
Adults of this species were encountered in large numbers on the first sampling day and the species remained abundant for the following 11 weeks before numbers began to decrease from week 12. The species was poorly represented during weeks 13–15, before finally disappearing in week 16. The species was not collected throughout winter and most of spring, but reappeared in moderate numbers on week 42. The species was fairly common during weeks 42–47, before again being fairly abundant on week 48. For some unknown reason, the species suddenly disappeared from samples taken during weeks 49 and 50 before reappearing in low numbers on week 51 and in greater numbers on week 52. This species was, without doubt, the most commonly encountered species, especially in the upper field, during the survey, being present for some 26 weeks of the year.
This small species was invariably swept from long grass with very few actually being sighted. None were encountered mating or with prey. The species appears to be largely confined to
Material from Jacana has been compared with specimens collected during the Queen Elizabeth Park survey (
Grassland inhabiting Asilidae encountered at Jacana Eco Estate (arranged alphabetically): 4 Caenoura annulitarsis (Loew, 1858) 5 Damalis monochaetes Londt, 1989 6 Dasophrys fortis Londt, 1981 7 Dasophrys tarsalis (Ricardo, 1920) 8 Dysclytus firmatus (Walker, 1857) 9 Euscelidia vallis Dikow, 2003 10 Ischiolobos mesotopos Londt, 2005 11 Leptogaster sp. 12 Microstylum sp. 13 Rhipidocephala obscurata Oldroyd, 1966. Photos: B. Muller.
A comparison of Asilidae collected at two survey sites (species listed in the order collected at Jacana Eco Estate). Jacana data taken from Table
| Species | Jacana Eco Estate | Queen Elizabeth Park |
|---|---|---|
| Euscelidia vallis | 1–15, 42–52 (25 weeks) | 1–18, 41–52 (29 weeks) |
| Ischiolobos mesotopos | 1–6, 45–52 (14 weeks) | 1–16, 52 (17 weeks) |
| Caenoura annulitarsis | 5–20 (16 weeks) | 1–20, 48–52 (25 weeks) |
| Dasophrus androclea | 11 (1 week) | 18 (1 week) |
| Neolophonotus wroughtoni | 21–22 (2 weeks) | 20–36 (17 weeks) |
| Leptogaster sp. | 38 (1 week) | 10–16 (7 weeks) |
| Microstylum sp. | 45–52 (8 weeks) | 45–49 (5 weeks) |
| Dasophrys fortis | 51 (1 week) | 13 (1 week) |
| Rhipidocephala obscurata | 51 (1 week) | 3–5, 48–52 (8 weeks) |
Ischiolobos mesotopos
Remarks
This species was described mainly on a good series of specimens collected during the year-long survey of a grassland within Queen Elizabeth Park (29°34'S, 30°19'E), Pietermaritzburg, when it was identified merely as “Species X” (
Adults of this species were encountered in good numbers on the first sampling day and the species remained abundant for the following three to four weeks before numbers began to decrease in weeks five and six. From week seven through to week 44, the species was absent, only reappearing in week 45. By week 49, the species was again fairly abundantly represented. The flight period of this species was therefore 14 weeks. The species appeared to be fairly uniformly distributed in both the upper and lower fields.
This small species was invariably swept from long grass with very few actually being sighted. None were encountered mating or with prey. The species appears to be largely confined to
Table
Pegesimallus bicolor
Remarks
This species was reviewed along with other Afrotropical species and recorded from a number of localities in KwaZulu-Natal and the Eastern Cape Province (
Only a single adult female of this species was collected in the first week of the survey. The genus is not commonly encountered in grassland situations, species generally preferring indigenous forests and their margins (
Members of the genus are active fliers and so it is highly likely that the encountered specimen was moving from one suitable habitat to another or had been swept into the area by wind.
Caenoura annulitarsis
Remarks
This fairly widely-distributed grassland species was reviewed by
At Jacana, adults of this species were encountered in low numbers on week five of the survey. By week eight, numbers had increased and by week 11, the species was considered abundant. Numbers began to decline from week 16 and the species had disappeared by week 21; the total flight period of adults being 16 weeks. The species was more commonly encountered in the upper field.
This relatively small species was invariably swept from grass with very few actually being sighted. None were encountered mating or with prey. The species appears to be largely confined to
Table
Pegesimallus pedunculatus
Remarks
This widely-distributed and commonly encountered Southern African species was reviewed along with other Afrotropical species and recorded from many South African localities, as well as some in the neighbouring countries of Mozambique, Namibia and Zimbabwe (
A single adult female of this species was collected in week seven of the survey. The genus is not commonly encountered in grassland situations, but generally prefers indigenous forests and their margins (
Members of the genus are active fliers and so it is highly likely that the encountered specimen was moving from one suitable habitat to another or had been swept into the area by wind.
Melouromyia natalensis
Remarks
This widely-distributed and fairly commonly encountered Southern African species was reviewed by
A single adult female of this species was collected in week seven of the survey.
Damalis monochaetes
Remarks
Damalus Fabricius, 1805, was revised by
Adults of this species were first encountered, in moderate numbers, in week 10. The species then became abundant over the following six weeks (weeks 11–16). Numbers then diminished over the next three weeks (17–19) and none were encountered on and after week 20. The species was almost entirely confined to the lower field in an area adjacent to trees bordering the estate (most species appear to inhabit vegetation adjacent to wooded areas).
This moderately sized, rather active species was almost invariably seen flying over the vegetation and was easy to catch. Although none were encountered with prey, tail-to-tail mating pairs were commonly observed. The species appears to be largely confined to
Dasophrys androclea
Remarks
Afrotropical Dasophrys Loew, 1858 were revised by
A single adult male of this species was collected in week 11 of the Jacana survey.
Table
Dasophrys tarsalis
Remarks
Afrotropical Dasophrys Loew, 1858 were revised by
Adults of this species were common to abundant between the late autumn weeks 12 and 18. None were encountered in weeks 19 and 20, while a single specimen was found in week 21. All specimens were collected in the lower field.
This moderately large species was almost invariably encountered flying fairly close to the ground where individuals perched on low vegetation. None were encountered mating or with prey. The species appears to be largely confined to
Neolophonotus wroughtoni
Remarks
This species, a member of the large comatus species group, was reviewed by
Only two specimens were collected during the winter at Jacana, one each on weeks 21 and 22, respectively. Adults were found resting on the ground and clearly belong to
Table
Dasophrys umbripennis
Remarks
This species was originally described mainly from the Pietermaritzburg district (
A single adult male was collected in week 28.
This distinctive species was swept from long grass. Its patterned wings are almost certainly an adaptation to forest or forest margin habitats, i.e.
Neolophonotus hirsutus
Remarks
This species, reviewed by
Adults of this species were encountered in low to moderate numbers during the four spring weeks 36–39. All encountered individuals were found in the lower field, especially in areas that had recently been burned.
This small to medium-sized species was invariably found resting on the ground or on vegetation close to the ground. While two specimens were collected with Diptera prey, others were swept from long grass with very few actually being sighted. The species appears to be largely confined to
Neolophonotus variabilis
Remarks
This somewhat variable species, a member of the suillus species group, was described using many specimens collected mainly in KwaZulu-Natal, but also recorded from various localities in the Eastern and Western Cape provinces (
Single specimens were collected at Jacana in weeks 36 and 39, fair numbers were then encountered in weeks 41–45 and a single specimen was collected in week 46. Although the species was not encountered in weeks 47–51, a single specimen was netted in week 52. Although the flight period spanned some 17 weeks (from week 36 to 52), the species appeared to be most active in late spring between weeks 41–45. All encountered individuals were found in the lower field.
This species was usually observed resting on the ground or on vegetation close to the ground and is considered belonging to
Leptogaster
Remarks
Leptogaster Meigen, 1803 is a large genus, with over 50 described Afrotropical species, that is in need of modern revision (
A single male specimen, requiring specific identification, was collected in Jacana’s upper field on week 38 of the survey.
This small species was swept from long grass and is considered to belong to
A comparison of material from Jacana and Queen Elizabeth Park strongly suggests that only a single species is involved. While Table
Microstylum
Remarks
Microstylum Macquart, 1838, with 90 catalogued Afrotropical species, 79 listed as valid and 11 as synonyms (
Adults of this summer active species were encountered in large numbers from week 45 through to week 48 when numbers declined. The species was ‘uncommon’ in week 52, the last week of the survey, with only a single specimen being seen and captured.
This large, almost entirely black species was invariably seen flying strongly over the vegetation, mainly in the lower field. Although a number of mating pairs were encountered, none were observed feeding. The species appears to be best accommodated within
Although Table
Dysclytus firmatus
Remarks
Dysclytus Loew, 1858, is currently monotypic, with firmatus being considered the only valid species. In his handling of the genus,
Adults of this species had a relatively short period of activity in summer, being encountered in fair numbers in weeks 46–48, while a single specimen was collected in week 49. The species was invariably encountered in the lower field.
This fairly large and distinctive species was almost invariably seen flying over or between grass clumps and coming to rest on vegetation. While none were encountered mating, one female was collected with prey, a small cicada (Cicadidae). The species appears to be largely confined to
Dasophrys fortis
Remarks
This female is almost certainly confined to
Rhipidocephala obscurata
Remarks
Although a single female, swept from grass on week 51 of the Jacana survey, keys out to R. obscurata using
The species is probably confined to
Table
Discussion
Eighteen species of Asilidae were encountered at Jacana, two fewer than recorded during an earlier survey at Queen Elizabeth Park (
Although 18 species were encountered during the survey, the largest number encountered on any one occasion was five, less than a third of the species inhabiting the area. It is, therefore, obvious that a proper understanding of the invertebrate fauna of any particular locality probably requires a number of strategically planned sampling occasions.
Of particular interest, but not unexpected, is the fact that very few Asilidae were encountered during winter (weeks 19–31) and early spring (weeks 32–35). The planned burning of the grassland which took place during the spring weeks of 35, 36 and 41 appears to have had little impact on asilid populations. While some ground inhabiting species of Neolophonotus were encountered in spring and the emergence of E. vallis, a dominant grass inhabiting species, commenced on week 42, the burning of the grassland did not appear to have any significant impact on asilid life cycles. However, the fact that E. vallis began emerging at the time of the last burn (week 41) strongly suggests that earlier burns, timed with the end of winter or start of spring, would be preferable.
Also of interest was the fact that some species appeared to be mostly confined to either the upper or lower fields. The upper field, being larger, higher and more exposed may be more suitable for some species while the lower field, being lower and more protected by bordering trees may offer more suitable environmental conditions for other species. Another possible factor which may be of importance is the existence of the access road that separates the fields. This roadway, which has been lined with trees, may well constitute a barrier restricting dispersal between the two fields. Efforts to minimise the possible impact of this access road should be contemplated.
While a more detailed comparison of the results obtained during the survey of Queen Elizabeth Park (
Acknowledgements
Paul Kotze, developer of the Jacana Eco Estate, is thanked for allowing me to undertake regular visits to the estate and for providing me with some of the documentation issued before the development commenced. With his permission, Julie Dakers of Catchway Properties (Pty) Ltd kindly supplied me with architectural plans and aerial photos of the estate. Drs John Midgley and Kirstin Williams of the KwaZulu-Natal Museum, Pietermaritzburg, provided unlimited access to collections and associated services, for which I am grateful. Burgert Muller (National Museum, Bloemfontein) kindly generated the map of the estate and photographs of Asilidae. Alison Young (Botany Department, University of KwaZulu-Natal, Pietermaritzburg), is thanked for undertaking identifications of plants encountered at Jacana during the survey. Financial support was kindly provided by both the University of KwaZulu-Natal and the Foundation for Research Development. The continued support and encouragement of my wife Ann is also appreciated.
References
- Dikow T (2003) Revision of the genus Euscelidia Westwood, 1850 (Diptera: Asilidae: Leptogastrinae). African Invertebrates 44(2): 1–131.
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