Earlier this year I had been studying the behaviour of three antlion larvae in a tray of sand. These had been ‘captured’ from a site in the DunwichForest and when finished there was no opportunity to return them and so the sand and antlions were tipped at the base of a South-facing wall, beneath a large Campsis vine. An occasional glance when passing showed that they had settled down in their new home, making pits about 25mm in diameter, comparable with pits in the wild. After a time activity ceased and the sand became covered in falling leaves and I thought little more about them.

Imagine my surprise, and excitement, when (mid – October) I saw that there were a number of small pits scattered over the sand or perhaps they were just where large raindrops had landed? To check, the sand was gently brushed over; within 15 minutes small wandering ploughed tracks had appeared (a reminder of the American name for antlions, ‘doodle bugs’) and after an hour seven pits were visible. Next morning this had increased to eleven.Clearly the antlions were back! Two pits were scooped and the sand examined under a microscope where two very small antlions (c. 1 - 2 mm long) were behaving as antlions do, walking backwards, hoping quickly to become invisible under the sand.

This observation poses questions about antlion behaviour and provides opportunities for their easier observation.

The importance of isolated pine trees to provide ‘leks’ for mating antlions has been emphasised (Plant, 1998). In this case the nearest antlions on the heath are 900 m distant and the nearest isolated pine tree is in a garden c. 125 m from the garden antlions, thus questioning any possibilities of contact between the different groups or of visiting the lone pine. A more likely hypothesis seems to be that the garden antlions mated near to their sand pile and then returned to lay eggs; that they flew off to meet and mate with the heath antlions and then return seems unlikely. The chances that, even if all three of the original antlions made it to adulthood, they may all have been females raises the possibility of parthenogenesis, but so far I have found no leads for an answer to this question.

Frequent monitoring of antlion behaviour at a forest site is time consuming and having what appears to be a natural antlion site beside the garden path should make it easy for more or less constant observation. The regular topography of the site, compared with the humps and bumps of the banks in the forest should make it possible to map the position of pits and how they may move from time to time. So far most of the pits have been made about 30 mm from the wall, about the same distance from the nearest neighbour and at the highest point on the sand heap (Photo). The next question is, if the sand is dry enough, will they remain active through the winter?

Reference

Plant, C. W. (1998) Investigations into the distribution, status and ecology of the ant-lion Euroleon nostras (Geoffroy in Fourcroy, 1785) (Neuroptera: Myrmeleontidae) in England during 1997. Transactions of the Suffolk Naturalists Society 34: 69-79

Michael Kirby

e-mail: e_j_m_kirby@btinternet.com

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