Boros István (szerk.): A Magyar Természettudományi Múzeum évkönyve 52. (Budapest 1960)
Móczár, L.: The loess wall of Tihany and the nesting of Odynerus spiricornis Spin. (Hymenoptera, Eumenidae)
II. The period and methods of the investigation, and the numbers of the animals observed For the sake of finding out the maximal population, I have repeatedly visited the loess wall during the breeding period. After the preceding rainy days, the sun broke through on 19 June 1959, and there were at most 3 Odynerus on the wing per m 2 at 2 p. m. at 26,4°C (clouds 4). On 6 July, the sky was overcast (clouds 5 at 2 p. m.), it cleared up several times ; there were about 10 wasps per m 2 , at a temperature of 26,4°C. Two of the wasps were carrying sawfly larvae into their nests. I made my investigations on 17—24 July. Unfortunately, the weather was, for the season, cold, i-tormy, rainy between 17—19 July (with a precipitation of 25,2 mm on 19 July), the temperature sank to 17—16,6°C, the wind was very strong (N4). It cleared up a bit only in the afternoon of 17 and 19, but even so, I could observe only 2—3 Odynerus along the whole loess wall. The cold weather and the continuous rains have not only decreased the Odynerus stock, but they even damaged the turrets. Several of them were washed away, many had their external surfaces swept smooth, indeed, numerous holes were stopped. The protruding ledges of the loess wall got wet to a depth of 10—16 cm. On one square meter, there were 22 turrets under construction, 63 damaged ones, and many holes. In the forenoon of 20 July, there was yet a rainfall of 21,6 mm. In the afternoon (at 2 p. m.), it warmed up to 23,5°C at the Meteorological Station of the Biological Research Institute on the northern shore of the Peninsula, while it attainted 29°C, 10 cm from the loess wall on the southern shore. The clouds (value 5) have also dispersed for a short time. Four Odynerus specimens were active, one of them carrying a sawfly larve. From 4 p. m. on, the atmosphere got rapidly colder again, the temperature sinking to 21°C from 23°C in front of the wall at 6 p. m. The sky became overcast again, it thundered and the wind rose afresh (SW 1). A weather suitable for observations began only on 21 July. I measured the temperature data of the days 21—24 July, 10 cm in front of the wall and in every half hour (fig. 1). Though the température here is higher due to the reflexion of the heat waves, still the wasps work in this very place. Since the cells are laid generally 5 —6 cm deep, I paid also attention to the temperature of the loess wall to a depth of 6 cm. The fluctuation of the temperature was conspicuous only on 22 July, owing to the frequent formation of clouds. The loess wall warmed up evenly to a depth of 6 cm, and it was warmer than the outern atmosphere (by only 0,5°C) at 17 : 30 on 21 July. The data of the Meteorological Station of the Research Institute on the northern side of the Peninsula were lower than those measured at the wall. The differences between the two set of readings are justified if we take into account the differring nature of the sites and the above mentioned reflected radiation. The rays of the Sun namely fell on the loess wall, due to its western inclination, at 11 : 20, and then it was exposed to them till sunset. It was very warm on 30 July, but there were hardly anv flight in spite of the strong sunshine. I observed only a single Odynerus, just as it was carrying a sawfly larve into its nest high up on the wall. In order to survey the increased population due to the favourable weather, I marked mv Odynerus specimens, active on the several days of the observational period, by different kinds of colors. I marked by spots of a similar color the base 2o Természettudományi Múzeum Évkönyve
