S. Mahunka szerk.: Folia Entomologica Hungarica 59. (Budapest, 1998)

on the sand. During their walk - which is quite slow, they frequently change direction as if searching for something - first they are continuously waggling their abdomen and since the wings cover the abdomen they seem to be moving and flashing. Second, they are continuously touching the surface of the sand with their forelegs. Sometimes they stop and lift their forelegs into the air and move them as if to smell them. 3. They show a similar behaviour when another fly gets close to a Sphyracephala specimen. It tries to keep off the other fly with its forelegs even if it is twice as large as Sphyracephala itself. In addition they keep off another Sphyracephal specimen the same way. It could be observed well when we found a dead frog. About four dozen flies assembled on to the body. 7-8 of them were stalk-eyed, half f them were on the frog and the others close to the body on the sand. Those on the body seemed to be feeding, because they lowered their head down so their body were lent forward thus it was easily distinguishable from the normal position. Sphyracephala species cannot feed in another way because of their short proboscis (Peterson 1987, Papp et al. 1997). In only one other case we observed a Sphyracephala specimen to feed, when a single fly was feeding on a dead ant for only a short time. 4. In spite of the "territoriality" within short distances Sphyracephala specimens rarely occur lonely or in small numbers. Usually a number of flies are staying on a certain part of the river-bank not far from one another. Minimal density of specimens registered was 1 animal/m

2

, maximum was 12-15/m

2 and the mean is estimated to be 3-4 flies/m

2

. They can sense another fly from a distance of several cms, the moving of a man from 1-2 m. 5. A similar behaviour could be observed when we returned to the hibernating place in October of 1997. The number of assembling flies increased from severad to about 500 during a two-week period. When the number was high the flies formed groups and took place in patches on the wall with a maximum of 200 animals. They tolerated shorter distances between each other better than in summer and often settled on a root, leaf or twig on the high bank. Groups were attached to their locations: when we arrived many of the flies took off and flew away but later returned to the same place. Sen (1921) also reported large groups of S. hearseiana, S. brevicornis and other diopsids (Hennig 1941) REFERENCES Hennig, W. (1941): 39c. Diopsidae. - In: Linder, E. (ed.): Die Fliegen derpalaearktischen Region, 5 (7), Lieferung 143, pp. 1-8. Papp, L., Földvári, M. and Paulovics, P. (1997): Sphyracephala europaea sp. n. (Diptera: Diopsidae) from Hungary represents a family new to Europe. - Folia ent. hung. 58: 137-146. Peterson, B. V. (1987): Chapter 61. Diopsidae, - In: McAlpine, J. F. et al. (eds): Manual of Nearctic Diptera. 2. Research Branch, Agriculture Canada, Ottawa. Agric. Can. Monogr. 28, pp. 785-789. Sen, S. K. (1921): Life-histories of Indian insects. Diptera Sphyracephala hearseiana, Westw. Mem. Dep. Agric. India ent. ter. 7: 33-38, 2 plates Author 's address: P. PAULOVICS Department of Ecology József Attila University Egyetem u. 2. H-6722 Szeged HUNGARY