The investigation into the sudden surge of insects that engulfed parts of Buffalo City in late August is continuing, with the municipality confirming that the insects have been identified as belonging to the Sciaridae family.
Buffalo City municipality (BCM) spokesperson Luzuko Buku said there had been a noticeable reduction in the number of insects, which the municipality has described as non-biting midges and flying gnats.
“Though there is a clear reduction of non-biting midges and flying gnats, the municipality would like to inform residents that investigations are ongoing to determine the actual source in order to see ways of curtailing them,” Buku said.
He said studies conducted through partner institutions, co-ordinated by the municipality’s department of economic development and environmental affairs, had identified the insects as belonging to the Sciaridae family.
However, species-level identification remained outstanding.
“There will be further investigation of the occurrence of unusually high numbers of these insects across multiple areas of Buffalo City municipality,” Buku said.
Entomologist Prof Terence Bellingan, from the Rhodes University department of entomology in Makhanda, said identifying insects from descriptions or photographs alone could be difficult, particularly given the diversity of true flies.
“From the description provided, it is very difficult to say what kind of insect, fly, is involved,” Bellingan said.
He said specimens recently sent to him by colleagues from the department of economic development, environmental affairs and tourism’s scientific services in Qonce had been identified as belonging to the Sciaridae family.
“These are commonly known as black fungus gnats, are non-biting midges, and could be the same ones referred to. But without being able to make a comparison it is impossible to be sure.”
Bellingan said there were numerous fly species that could potentially fit the description, while a lack of scientific literature, specialist expertise and properly identified museum specimens could further complicate identification.
He also cautioned against claims that the insects could complete their life cycle in three to four days.
“Each species will have its own biological traits and characteristics that determine developmental rates under specific conditions,” Bellingan said.
Using the Sciaridae specimens he had examined as an example, he said information from the Afrotropical Diptera manual indicated life cycles of between 15 and 135 days in temperate zones, depending on temperature and moisture.
“A time frame of three to four days is therefore very unlikely, assuming we are talking about the same group of flies,” he said.
Bellingan said environmental conditions could, nevertheless, have played a role in the sudden increase.
“It is generally accurate to say that insects will respond to environmental cues quite closely, which will sometimes lead to higher or lower numbers of a particular insect, or group of insects, depending on their particular biological traits.”
He said determining whether the current numbers represented an unusually large population boom would require longer-term population data.
“Whether it constitutes an unusually large population boom, that would depend on the populations that came before and those that come after,” Bellingan said.
Environmental specialist Kevin Cole said warmer weather followed by rainfall could create favourable conditions for the insects to reproduce.
“The warmer weather experienced, followed by rainfall, creates ideal breeding conditions,” Cole said.
Recent above-average rainfall had resulted in standing water, saturated soils and swampy areas, he said, while organic material associated with sewage and contaminated runoff could provide food for midge larvae.
“Broken sewage pipes, contaminated runoff into rivers and stormwater systems, and exposed sewage supply organic matter that midge larvae feed on," Cole said.
"This allows a much higher percentage of larvae to survive and emerge as adult swarms.”
Marile van Niekerk of Biodynamic Women Farmers said the surge could also be viewed as an indication of changing environmental conditions rather than simply a pest problem.
“In a biodynamic approach, a sudden outbreak of midges or gnats is not automatically seen as something that needs to be poisoned," she said.
"It is first seen as an indication that something in the environment has changed and that the farm ecosystem is responding to that change.”
Van Niekerk said moisture, decaying organic matter, disturbed soil, stagnant water, changes in vegetation and the weather could all influence insect populations.
“Rather than immediately asking, ‘How do we get rid of them?’, we should ask, ‘Why are they here in such numbers now?’” she said.
This approach, Van Niekerk said, did not mean ignoring an outbreak, but rather investigating its underlying causes before intervening.
“Observe, investigate the cause, address the conditions, restore balance, intervene only where necessary,” she said.
Bellingan said that if the insects were confirmed to be the black fungus gnats he had examined, they would not pose a threat to people.
“Black fungus gnats cannot bite and do not transmit diseases to humans,” he said.
He said that such insects could form part of healthy ecosystems, acting as decomposers and providing food for birds, bats, spiders and other insects.
Back in Buffalo City, the municipality has cautioned against attributing the insect surge to any particular municipal facility.
“It should thus be noted that at this stage, no particular municipal facility should be identified as the source without supporting field evidence. Further investigations are therefore still ongoing,” Buku said.
The municipality, he said, was encouraged by the decline in insect numbers and sought to reassure residents.
“The investigation confirms that the insects pose no health threat and do not bite,” Buku said.
Residents have been urged to report concerns to the municipality’s environmental health unit.
Buku said BCM was continuing to work with specialists and entomologists from other relevant departments.
“We are continuing to collaborate closely with specialists and entomologists from partner departments to monitor the situation.
"We will continue to provide further updates on this,” he said.
