Shevtchenkella serrata (Nalepa, 1892)

Chetverikov, Philipp E., Desnitskiy, Alexey G., Klimov, Pavel B., Ozman-Sullivan, Sebahat K., Romanovich, Anna E. & Sukhareva, Sogdiana I., 2023, Tuerkayana rotundum, Zoological Studies 62 (35), pp. 1-18 : 14

Shevtchenkella serrata from Acer platanoides

Detailed 2020‒2021 seasonal data on S. serrata was presented by Chetverikov et al. (2022). Here we complement it with confirmatory observations performed in 2022. In brief, both morphotypes of S. serrata (protogynes and deutogynes) were found feeding on the epidermal tissue on the lower leaf surfaces of A. platanoides , as well as on the epidermis of the pericarp of immature samaras still attached to the parent trees in August 2020. In autumn 2020 and up to early December 2020, they were observed near terminal buds and in crevices on young stems and on the fallen maple samaras. Motionless deutogynes were detected on the samaras on the ground at the end of March 2021. In April 2021, solitary deutogynes were observed near the soil level on the hypocotyls of young seedlings, and in the space between unseparated juvenile leaves ( Fig. 8A, B arrows). In the middle of May 2021, actively moving deutogynes were found on the lower surface of cotyledons and on the petiole bases and leaves of seedlings, saplings ( Fig. 8C, D, E arrows) and large maple trees growing nearby. In the middle of June 2021, numerous protogynes, males and immatures suddenly appeared on the same branches of the maple trees that had been sampled earlier in spring 2021 and on seedlings and small saplings, together with deutogynes. During July 2021, only protogynes (maximum 480 per leaf) were present in the samples. However, in August 2021, we detected both deutogynes and protogynes on maple leaves. They were both present on leaves and samaras from mid-August 2021 until the leaves began to fall in autumn, after which they were again detected on the samaras on the ground. Similar to the 2021 observations, in April and May 2022, solitary deutogynes were found on maple seedlings; in early June 2022 the first protogynes appeared and coexisted with deutogynes; in July 2022, protogynes were present but deutogynes were absent; and in early August 2022, both morphotypes were again found in sympatry on leaves and immature samaras.

Brevulacus reticulatus from Quercus robur

At the end of May 2021, 1‒4 brownish deutogynes of B. reticulatus were found on the lower surface of leaves of the two model Q. robur trees. At the beginning of June 2021, the first protogynes were recorded and deutogynes were still present on leaves, although some of them were not moving and considered to be likely dead. In late June 2021, only protogynes, males and immatures were found on Q. robur leaves. In July 2021, deutogynes were not recorded and appeared again on leaves at the beginning of August 2021 only. Solitary protogynes were observed feeding on green, immature acorns in mid-July and early August, 2021. However, by the time the acorns hardened in autumn, no mites were found on them or on the acorns on the ground. Also, we did not find any eriophyoids on the numerous oak seedlings that were around the two model Q. robur trees. Up to the end of September 2021, deutogynes and protogynes were present together on the leaves. During September 2021, the number of protogynes gradually decreased. In October and December 2021, groups of 3–12 motionless deutogynes were observed overwintering near buds. The first overwintered deutogynes were detected slowly moving near buds at the beginning of May 2022. At the end of May 2022, they were observed laying eggs on young Q. robur leaves, and at the beginning of June 2022, mixed colonies containing the first generation of protogynes and very sparse deutogynes were observed on Q. robur leaves.

Figures

Fig. 8. Locations (arrows) of overwintered females of Shevtchenkella serrata collected on 18 April 2021 (A, B) and on 16 May 2021 (C, D, E) from seedlings (A, B, C) and saplings (D, E) of Acer platanoides from North-West Russia.