Psenulus fuscipennis (Dahlbom, 1843)

Martynova, K. V. & Fateryga, A. V., 2014, Omalus Sculpticollis As The Main Enemy Of Psenulus Fuscipennis (Hymenoptera: Chrysididae, Crabronidae) In The Crimea, Ukraine, Vestnik Zoologii 48 (1), pp. 11-26 : 13

Psenulus fuscipennis (Dahlbom, 1843)

In total 95 nests of P. fuscipennis were obtained. The diameter of stems with wasp nests varied from 5. 0 to 7.7 mm; the number of cells per nest varied from 5 to 31 (mode — 18, average — 16.5). The total number of cells was 1503. Mortality was observed in 97 (6.5 %) cells: in 68 cases at the egg stage, in 29 cases as young larvae.

Other 621 (41.3 %) cells of P. fuscipennis were occupied or destroyed by different wasp enemies:

435 — by Omalus sculpticollis Abeille, 1878 ( Hymenoptera , Chrysididae ), though only 90 specimens of O. sculpticollis were found in the nests overall;

116 — by Melittobia acasta Walker, 1839 ( Hymenoptera , Eulophidae );

38 — by Trichodes apiarius (Linnaeus, 1758) ( Coleoptera , Cleridae );

32 —by Perithous septemcinctorius (Thunberg,1822) ( Hymenoptera , Ichneumonidae ( fig.2 ).

The final results are that O. sculpticollis is the main regulator of P. fuscipennis abundance. As a consequence, only the 52.2 % of P. fuscipennis emerged from their nests. Psenulus fuscipennis were at a prepupal or pupal stage during the examination of the nests in the third decade of April. The emergence of imagoes took place about two months later, at the end of June. Consequently, we conclude that this species overwinters as prepupa enclosed in cocoon.

Previously P. fuscipennis was reported as monovoltine species, at least throughout Italy ( Bonelli, 1988). In the present study the 11.1 % of P. fuscipennis emerged in summer, before the removal of the sheaves. In fact, we found 87 cells in 16 nests (the 5.8 % of the cells) with empty cocoons. The cells with abandoned cocoons were the outermost, being constructed last. Only one nest was completely empty — all cells contained abandoned P. fuscipennis cocoons. Apparently a part of the studied population of the crabronid wasp gave rise to the so called “facultative generation”, while the rest of the offsprings was monovoltine.

Figures

Fig. 2. Reproductive success and mortality of Psenulus fuscipennis progeny caused by different enemy species and other affects (in terms of number of cells). Рис. 2. Репродуктивный успех и гибель потомства Psenulus fuscipennis от различных видов врагов и других факторов (в перерасчёте на количество ячеек).