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)
during the 2 months. According to Nielsen (1945), the Bembex larve reaches the so-called transitional ,, pseudochrysalide" state soon after it had spinned its cocoon. Its head turnes toward the abdominal side and the shape of its body also changes. However, the head of the Bembex larve is closely appressed to its abdomen in March (cf. figure 1. c), while, on a photograph made of the larvae in May, their head is free, though their body is still curved. To wit, the figures present the two types of larval behaviour as found also in 0. spiricornis, with the difference that the Odynerus larve thought to be older is in fact the younger in Nielse n's interpretation. A thorough examination of the gradual development of the larvae is therefore all the more justified. Though it is highly probable that the wasps visit their turrets even after 20 days (cf. marking experiences), it was not discovered whether this time be enough for the greyish-white larve to shrink into a yellow one. If this does not happen within 30 days, — the supposedly maximal life span of the wasps — then the different larvae found in the identical nest could not have descended from the identical parents ! Consequently, a mingling really exists : the possibility of intrusion into alien nests and the construction there of further cells, — in which connection we should bear in mind the pictures (Plate III, fig. 10) of certain phenomena, namely the quarrel of two Odynerus at the entrance of the turret, or the observation of another wasp which reappeared, together with its sawfly larve in the mouth of the turret, drew out the larve and flew away with it. Rey (1946) also reports on the intrusion into an alien nest in connection with a case, when he sealed up a nest of 0. spinipes L. while the wasp was away for provisioning larvae. Looking in vain for the entrance on its arrival, the wasp throw away the larve and began to dig a fresh cell in an alien nest, whose rightful owner was taken captive in the meantime by Rey. And this intrusion into an alien nest would, in its essentials, foreshadow a sudden, qualitative change of insect aggregates : that of the evolution of insect societies. Some wild bees construct tbeir own cells from a common burrow. And if a mother perishes from some cause, the remaining store may be used by a neighbour or even supplement the provisions of the alien larve. The caring for the alien larve is the deciding step which transforms the solitary wasp or wild bee into a social insect, which binds it to the nest, and which will be indirectly instrumental in the increased egglaying of the oldest female. Summary Of the xenocoen, tychocoen, eurycoen and parasitic species living on the loess wall of the Tihany Peninsula, I studied the eucoen Odynerus spiricornis Spin. To find out the maximal population, I observed, and intensively so on 20—24 July 1959, the life of this wasp on four occasions. I marked with dailychanged lacquer paint colours the several specimens and the nests they visited. The sawfly larvae carrying wasps are least sensitive against a marking by paints or a cooling off process. I made half-hourly readings of the atmospheric temperature 10 cm in front of the loess wall together with measuring also the temperature of the wall in a depth of 6 cm, in the vicinty of the cells. The highest number of wasps were active on 6 and 21 July on the wall. They visited 1 nest during 5 days, 4 during 4, 3 during 3, 10 during 2, and 14 nests during only 1 day ; 2 nests were visited even after 20 days. The selection of the nesting place takes some few hours or several days. The exact place of the nest-to-be is wetted and thus softened by some water, 26 Természettudományi Múzeum Évkön yvc
