04/02/2020
Over the past week or so we have been blessed with millions of butterflies flying over the country. Unfortunately, over the years many myths and unsubstantiated โfactsโ have also crept into the story of these amazing creatures.
๐๐ช๐ต๐ฉ ๐ต๐ฉ๐ข๐ต ๐ช๐ฏ ๐ฎ๐ช๐ฏ๐ฅ, ๐ฉ๐ฆ๐ณ๐ฆ ๐ข๐ณ๐ฆ ๐ต๐ฉ๐ฆ ๐ฎ๐ฐ๐ด๐ต ๐ค๐ฐ๐ฎ๐ฎ๐ฐ๐ฏ ๐ฒ๐ถ๐ฆ๐ด๐ต๐ช๐ฐ๐ฏ๐ด ๐ธ๐ช๐ต๐ฉ ๐ข๐ฏ๐ด๐ธ๐ฆ๐ณ๐ด ๐ต๐ฉ๐ข๐ต ๐ข๐ณ๐ฆ ๐ข๐ด๐ฌ๐ฆ๐ฅ ๐ข๐ฃ๐ฐ๐ถ๐ต ๐ต๐ฉ๐ฆ๐ด๐ฆ ๐ฃ๐ถ๐ต๐ต๐ฆ๐ณ๐ง๐ญ๐ช๐ฆ๐ด ๐ข๐ด ๐ค๐ฐ๐ฎ๐ฑ๐ญ๐ช๐ฆ๐ฅ ๐ฃ๐บ ๐๐ฉ๐ฆ ๐๐ฆ๐ฑ๐ช๐ฅ๐ฐ๐ฑ๐ต๐ฆ๐ณ๐ช๐ด๐ต๐ดโ ๐๐ฐ๐ค๐ช๐ฆ๐ต๐บ ๐ฐ๐ง ๐๐ง๐ณ๐ช๐ค๐ข (๐๐ฆ๐ฑ๐๐ฐ๐ค ๐๐ง๐ณ๐ช๐ค๐ข)
๐ญ ๐ช๐ต๐ฎ๐ ๐ฎ๐ฟ๐ฒ ๐๐ต๐ฒ ๐๐ต๐ถ๐๐ฒ ๐ฏ๐๐๐๐ฒ๐ฟ๐ณ๐น๐ถ๐ฒ๐ ๐๐ต๐ฎ๐ ๐ฎ๐ฟ๐ฒ ๐๐ฒ ๐๐ฒ๐ฒ๐ถ๐ป๐ด?
Most of the butterflies being seen in Johannesburg and surrounding areas at the moment are Pioneer Caper Whites (Belenois aurota). This butterfly is also known as the Brown-veined White in South Africa, but the Lepidopteristsโ Society of Africa (LepSoc Africa) is currently trying to standardise the English names of all butterflies found in Africa. Belenois aurota occurs in southern Asia as far east as India and the Himalayas, in southern Arabia and throughout most of sub-Saharan Africa.
๐ฎ ๐ช๐ต๐ฒ๐ฟ๐ฒ ๐ฑ๐ผ ๐๐ต๐ฒ ๐ฏ๐๐๐๐ฒ๐ฟ๐ณ๐น๐ถ๐ฒ๐ ๐ฐ๐ผ๐บ๐ฒ ๐ณ๐ฟ๐ผ๐บ ๐ฎ๐ป๐ฑ ๐๐ต๐ฒ๐ฟ๐ฒ ๐ฎ๐ฟ๐ฒ ๐๐ต๐ฒ๐ ๐ต๐ฒ๐ฎ๐ฑ๐ถ๐ป๐ด ๐ฎ๐ป๐ฑ ๐๐ต๐?
The phenomena we are seeing at present is not a true migration (the butterflies will not return) but is a dispersal event. Butterflies are largely flying from the drier southwestern areas to the wetter northeast areas. All the butterflies are flying in a generally north-easterly direction. The core population of Belenois aurota in South Africa is the Kalahari region, where the larvae feed on Shepherdโs trees (Boscia albitrunca). The current โmigrationโ โ at least in the Johannesburg area โ appears to be the largest since 1966.
๐ฏ ๐๐ผ๐ ๐น๐ผ๐ป๐ด ๐๐ถ๐น๐น ๐๐ต๐ฒ ๐บ๐ถ๐ด๐ฟ๐ฎ๐๐ถ๐ผ๐ป ๐น๐ฎ๐๐?
The dispersal is due to a population explosion and will probably last for a few weeks.
๐ฐ ๐๐ ๐ฐ๐น๐ถ๐บ๐ฎ๐๐ฒ-๐ฐ๐ต๐ฎ๐ป๐ด๐ฒ ๐ฟ๐ฒ๐๐ฝ๐ผ๐ป๐๐ถ๐ฏ๐น๐ฒ?
Climate is definitely a factor, although we donโt think there is adequate data to suggest that climate change is responsible for the current wave of Pioneer Caper Whites / Brown-veined Whites. The triggers are twofold: Successive years of drought leading to drastic reductions of the predators that feed on Belenois aurota, primarily the eggs, larva and caterpillars. These predators may be viruses, parasitic wasps (parasitoids), robber-flies, spiders, birds etc. Usually about 99% of butterfly early-stages are eaten!
Good rainfall, as weโve experienced recently, leads to favourable conditions and a population explosion of Belenois aurota and a subsequent โmigrationโ.
๐ฑ ๐๐ผ๐ ๐ณ๐ฎ๐ฟ ๐ฑ๐ผ ๐๐ต๐ฒ ๐ฏ๐๐๐๐ฒ๐ฟ๐ณ๐น๐ถ๐ฒ๐ ๐ณ๐น๐ ๐ฎ๐ป๐ฑ ๐ต๐ผ๐ ๐ผ๐ณ๐๐ฒ๐ป ๐ฑ๐ผ ๐๐ต๐ฒ๐ ๐ป๐ฒ๐ฒ๐ฑ ๐๐ผ ๐ณ๐ฒ๐ฒ๐ฑ? ๐๐ผ ๐๐ต๐ฒ๐ ๐๐น๐ฒ๐ฒ๐ฝ ๐ผ๐ฟ ๐น๐ฎ๐ ๐ฒ๐ด๐ด๐ ๐ผ๐ป ๐๐ต๐ถ๐ ๐ท๐ผ๐๐ฟ๐ป๐ฒ๐?
We donโt really know how far individual butterflies fly in South Africa, but it seems likely that those that are high-flying and caught in favourable winds, can travel in excess of 1000 km. Those bobbing along near the ground (and feeding in Johannesburg gardens along the way), probably have a range of a few hundred kilometres - they will sleep at night, on a plant or grass stem. Note that not all the butterflies that we are seeing come from the Kalahari; local Pioneer Caper Whites / Brown-veined Whites will be emerging and joining in the โmigrationโ. Female Belenois aurota will lay eggs on suitable larval food plants (members of the Caper family) during their journey.
๐ฒ ๐๐ ๐ถ๐ ๐ธ๐ป๐ผ๐๐ป ๐ต๐ผ๐ ๐บ๐ฎ๐ป๐ ๐ฏ๐๐๐๐ฒ๐ฟ๐ณ๐น๐ถ๐ฒ๐ ๐ณ๐ผ๐ฟ๐บ ๐ฝ๐ฎ๐ฟ๐ ๐ผ๐ณ ๐๐ต๐ถ๐ ๐ฎ๐ป๐ป๐๐ฎ๐น ๐บ๐ถ๐ด๐ฟ๐ฎ๐๐ถ๐ผ๐ป?
We donโt have accurate numbers and the amount varies from year to year, but we currently estimate that the number of butterflies currently on the wing extends into the billions.
๐ณ ๐ช๐ต๐ฎ๐ ๐ฎ๐ฟ๐ฒ ๐๐ต๐ฒ ๐ฏ๐ถ๐ด๐ด๐ฒ๐๐ ๐๐ต๐ฟ๐ฒ๐ฎ๐๐ ๐๐ผ ๐๐ต๐ฒ ๐ฏ๐๐๐๐ฒ๐ฟ๐ณ๐น๐ถ๐ฒ๐ ๐ฑ๐๐ฟ๐ถ๐ป๐ด ๐๐ต๐ถ๐ ๐บ๐ถ๐ด๐ฟ๐ฎ๐๐ถ๐ผ๐ป?
There are few significant threats to adult Pioneer Caper Whites / Brown-veined Whites, as we believe they are distasteful to birds and are generally left alone. A few will be caught by robber-flies or trapped in spider webs (or killed by spiders while they are sleeping) and several will be killed by cars and trucks! Steve Collins recalls, several years ago in Kenya, his father having to clear the car radiator-grill of dead butterflies, to prevent the engine overheatingโฆ
๐ด ๐๐ผ ๐ผ๐๐ต๐ฒ๐ฟ ๐๐ฝ๐ฒ๐ฐ๐ถ๐ฒ๐ ๐บ๐ถ๐ด๐ฟ๐ฎ๐๐ฒ?
Generally Pioneer Caper Whites / Brown-veined Whites are the biggest contributors to the โmigrationโ, but other species also disperse. One of these is the African Migrant (Catopsilia florella), which we believe migrates for similar reasons โ occasionally, numbers of Catopsilia florella exceed those of Belenois aurota. A few species of moth also โmigrateโ in large numbers, but this generally occurs at night and at high altitude, so is not often reported. It is even less well understood than the Belenois aurota migration! For interest, LepSoc Africa are trying to introduce โButterfliesโ as a general term for all Lepidoptera; โMothsโ, which is used for a diverse range of Lepidoptera outside of the Papilionoidea superfamily, will fall away.
๐ต ๐ ๐ถ๐๐ฐ๐ผ๐ป๐ฐ๐ฒ๐ฝ๐๐ถ๐ผ๐ป๐
A recent news article stated that the butterfly-migration originates on the West Coast and that they are flying to Madagascar. As noted above, in South Africa the start of the dispersal-relay is the Kalahari and, while itโs not impossible that one or two adults may reach Madagascar, this is definitely not their intended destination.
Despite conflicting reports, Belenois aurota caterpillars feed only on plants of the Caper family; they are not an agricultural pest and will do no damage to suburban gardens; their caterpillars are not army worms or lily borers, nor will they cause African Horse Sickness
๐ญ๐ฌ ๐๐๐ฟ๐๐ต๐ฒ๐ฟ ๐ฟ๐ฒ๐๐ฒ๐ฎ๐ฟ๐ฐ๐ต
One of our LepSoc Africa members, Reinier Terblanche, is currently busy with research on Belenois aurota. One of the amazing things that heโs discovered is that butterflies are genetically pre-programmed to disperse; individuals coded for dispersal have different coloured pupae.
