Pollinator effectiveness of a specialist bee exploiting a generalist plant—tracking pollen transfer by Heriades truncorum with quantum dots

Heriades truncorum (Megachilidae) is a specialist bee that forages on Asteraceae and collects pollen by tapping its abdomen on pollen-presenting florets which places the grains directly in the ventral scopa. We tracked pollen transfer by female H. truncorum between conspecific inflorescences of Inula ensifolia and Pulicaria dysenterica by labelling pollen with quantum dots. On average, bees transferred 31.14 (I. ensifolia) and 9.96 (P. dysenterica) pollen grains from the last visited inflorescence, 39% and 45% of which were placed on receptive styles. Pollen germination ratio is significantly lower for inflorescences of P. dysenterica visited by one H. truncorum (0.13%) compared with open control inflorescences (0.51%), which suggests that the bees mainly transfer self-pollen of these self-incompatible plants. Thus, a single visit by H. truncorum does not grant the plant high reproductive success, but the bees’ abundance and flower constancy might reduce this disadvantage.

Stelis Minima Schenck, 1859 (Hymenoptera: Apoidea: Megachilidae) - A Species of Wild Bee New to Polish Fauna

Summary The paper presents information on Stelis minima Schenck, 1859, a species of cleptoparasitic bee new to Polish fauna representing the family Megachilidae. Stelis minima. probably inhabits most of Europe except for the southern and northern parts of the continent. The species was also found in the southern part of Finland, where it reaches its northern range limit (ca. 62°N). During the years 2002- 2006 four specimens of S. minima were collected in the Kraków-Częstochowa Upland (1 male) and Roztocze region (2 females and 1 male). All specimens were observed close to nests of probable host species of solitary bees - Chelostoma campanularum (Kirby, 1802) and Heriades truncorum (Linnaeus, 1758). The female of Stelis minima can be distinguished from other Central European species by the following characteristics: rounded head, clypeus about 1.5 times wider than its length, legs black, hind basitarsus almost parallel sided (not broadened on the distal part), distances between punctures on mesopleurae ca. as big as their diameter, posterior margins of metasomal tergites (T) black and without lateral bands of hair, T1 or T1-2 with small, lateral, yellowish white maculae; the maculae are sometimes absent. The male Stelis minima can be separated from other Central European species by the following characteristics: clypeus short (not covering mandibles), legs black, distances between punctures on mesopleurae and tergites T4-5 ca. as big as their diameter, posterior margins of metasomal tergites black and without lateral bands of hair, T1-2 or T1-3 with small, lateral yellowish white maculae, posterior margin of seventh tergite with short mid-process, posterior margin of third sternite with triangular emargination in the middle, posterior margin of fourth sternite with a tooth-like, mid-process.