• John Mendelsohn

Mopane scale insects

Updated: Mar 7

When I came to Ongava in mid-2018 its vegetation was extremely sparse and dry. Little rain fell in the 2018/2019 summer, which led to even bleaker conditions during 2019. The summer of 2019/2020 was a little wetter, and that of 2020/2021 even wetter and better.

Very few mopanes and other trees flowered during those three summers. As I write in early February 2022 little rain has fallen in this, the summer of 2021/2022. Most trees and a few perennial grasses are green, but the rest of the landscape is grey and brown. Nevertheless, many trees have flowered and are now fruiting, probably riding on the benefits of the previous good rains in 2020/2021.

One more form of life is now abundant on the mopanes: the nymphs of scale insects. Their silvery scales – technically known as lerps – form on the leaves or green seed pods. The lerps protect the growing nymphs from the sun and desiccation. These are true bugs in the order Hemiptera and those at Ongava probably belong to the species known as the African mopane psyllid Retroacizzia mopani. The nymphs grow to about 3 millimetres in length before moulting into adults. Fructose and glucose sugars are present in the lerps. Birds and children enjoy these sweet delicacies, which are called uutushi in Oshikwanyama. I have often sampled them, and suggest you do the same.

The sweet lerps found on mopane leaves (left) and Mopane pod covered in scale insect lerps (high).

There is one nagging question: are the scale insects on leaves the same as those on seed pods? The smaller numbers of lerps found in 2020/2021 were sweet and on leaves, whereas the many lerps found in 2021/2022 were on seeds pods and tasteless. Why?

Thanks to Simeon Naholo, Hileni Mupopiwa and Elizabeth Shangano for introducing me to these fascinating insects.

Tiny nymphs exposed when their lerps were removed for the photograph above

References: Ernst WHO & Sekhwela MBM. 1987. The chemical composition of lerps from the mopane psyllid Arytaina mopane (Homoptera, Psyllidae). Insect Biochemistry 17: 905-909; and Oppong CK., Addo-Bediako, A, Potgieter MJ & Wessels DCJ, 2010. Nymphal behaviour and lerp construction in the mopane psyllid Retroacizzia mopani (Hemiptera: Psyllidae). African Invertebrates 51: 201-206.