Ecologica Montenegrina 32: 1-9 (2020) This journal is available online at: www.biotaxa.org/em http://dx.doi.org/10.37828/em.2020.32.1 Ecological characteristics of Thaumetopoea pityocampa Denis & Schiffermüller, 1775 (Lepidoptera: Notodontidae) in egg stage in Thasos Island, Greece MARGARITA GEORGIEVA*, MARIA MATOVA, GERGANA ZAEMDZHIKOVA, IVAILO MARKOFF, PLAMEN MIRCHEV & GEORGI GEORGIEV Forest Research Institute - Bulgarian Academy of Sciences, 132 ‘St. Kliment Ohridski’ Blvd., Sofia, Bulgaria *Corresponding author: E-mail: [email protected] Received 22 April 2020 │ Accepted by V. Pešić: 26 May 2020 │ Published online 2 June 2020. Abstract In September 2017, 96 egg batches of Thaumetopoea pityocampa were collected from Aleppo pine (Pinus halepensis) trees at four sites of Thasos Island in Greece. In the different localities, the average number of eggs in batches varied from 196.5 to 223.9 (212.4 for the Thasos Island). The length of P. halepensis needles with egg batches differed in size - between 84 to 210 mm. Approximately 75% of batches were laid close to the middle of needles, between 121 and 180 mm. The egg masses were formed mainly on two needles (84.4%) and the rest - on one, three or four needles (13.6%) or on fine shoots (2%). In most cases (88.3%), the female moths started to lay eggs from the tip of the needle. The distance from the base of the needle to the beginning of the egg batches was established between 0 and 180 mm, as most of them (62.7%) were clustered around the average value (87.3 mm) in the diapason of 60-120 mm. The average rate of T. pityocampa survival in egg stage was 48%. The parasitized eggs were 43.8%, and the rest included unhatched eggs, predominately undeveloped eggs with dried-up yolk. No correlation was found between the percentage of parasitized eggs and the distance of the egg batches from the base of needles. Key words: pine processionary moth, fecundity, ecology, egg parasitoids, Thasos Island. Introduction Pine processionary moth, Thaumetopoea pityocampa Denis & Schiffermüller, 1775 (Lepidoptera: Notodontidae) is one of the most dangerous insect pests in pine forests in the regions under Atlantic and Mediterranean climates in Europe, Middle East and North Africa (Roques et al. 2015). In Greece, T. pityocampa is distributed from sea level up to 1800 m where its occurrence is only limited by unsuitable weather conditions or geographic island isolation (Avtzis, 1983; Buxton, 1983). It infests both endemic and exotic pine species, with clear preference to Pinus halepensis Mill., P. nigra Arn. and P. radiata Don. Numerous studies were carried out in the country investigating the importance, significance and spatial distribution of T. pityocampa on pine species (Kailidis, 1962a; Avtzis et al. 2016; etc.). Most of them were focused on investigation of effective methods for control the pest distributions and factors regulating density in egg stage (Kailidis, 1962b; Bellin et al. 1990; Schmidt, 1988, 1990; Douma- Petridou et al. 1998; Schmidt et al. 1997a; Mirchev et al. 1999a, 2010; Tsankov et al. 1997, 1999; etc.). Ecologica Montenegrina, 32, 2020, 1-9 ECOLOGICAL CHARACTERISTICS OF THAUMETOPOEA PITYOCAMPA IN THASOS ISLAND Studies on the complex of egg parasitoids were conducted mainly in the continental parts of the country, but also in Hydra Island in Aegean Sea basin (Schmidt et al. 1997a). In 2017, in Thasos Island, an initial study on T. pityocampa egg parasitoids was explored in which four primary species and one hyperparasitoid were reported: Ooencyrtus pityocampae (Mercet, 1921) (Hymenoptera: Encyrtidae), Baryscapus servadeii (Domenichini, 1965), B. transversalis Graham 1991 (Hymenoptera: Eulophidae), Anastatus bifasciatus (Geoffroy, 1785) (Hymenoptera: Eupelmidae) and Trichogramma sp. (Hymenoptera: Trichogrammatidae) (Georgieva et al. in press). In island territories, studies on pine processionary moth are of high interest due to expectations for presence of specific ecological characteristics of the pest populations in isolated areas. Although females are able to fly no more than 2-3 km (Démolin, 1969), genetic exchange in T. pityocampa populations on islands is possible as the male moths fly at a distance up to 50 km (Mirchev et al., 2013). The aim of this investigation was to study the main ecological characteristics of T. pityocampa in egg stage in Thasos Island. Material and methods In the period 6-10 September 2017, a total of 96 T. pityocampa egg batches were collected from Aleppo pine (P. halepensis) trees at four sites of Thasos Island: Skidia (40°36'20.32"N, 24°43'36.12"E, 28 m a.s.l.), Thimonia (40°36'24.62"N, 24°43'14.71"E, 11 m a.s.l.), Alyki (40°36'21.11"N, 24°44'26.43"E, 18 m a.s.l.) and Panagia (40°43'43.00"N, 24°43'50.05"E, 351 m a.s.l.). The collected material was transported to the laboratory of entomology at Forest Research Institute in Sofia, Bulgaria. The scales of egg batches were removed, and the samples were analysed according to the protocol described in Tsankov et al. (1996). Each egg batch was individually placed in a test tube covered by a cotton stopper and kept under laboratory conditions (20-22 °C). In October 2018, the eggs without openings were dissected and analysed under a stereomicroscope (40×). Main characteristics of the collected samples were measured: length and number of needles wrapped by egg batches; distance of egg batches to base of needles; length (determined by two factors: number of rows and number of eggs in them) and diameter of egg batches; orientation of scales on egg batches; ratio of larval emergence, unhatched egg and parasitism ratios. The statistical analysis of obtained data were conducted by MS Excel 2013, Statistica for Windows 12 and Mann-Whitney U test (Hollander & Wolfe, 1973). Results A total of 20391 eggs of T. pityocampa were analyzed from four studied sites in Thasos Island (Table 1). The average number of eggs laid in a batch slightly varied from 196.5±65.7 (Alyki) to 223.9±43.1 (Thimonia), with an average of 212.4±51.9 for the Thasos Island. The number of eggs in individual batch, however, significantly ranged - from 34 to 297. Approximately 75% of the eggs were laid between 121 and 180 mm, close to the middle of needles (151.1 mm) (Fig. 1). The egg masses were formed mainly on two needles (84.4%) and single of them - on one, three or four needles as well as on fine shoots (2.0%). The number of rows in egg batches ranged between 6 and 13, with an average of 7.5-7.9 (Table 1). In the individual case of egg batch laid on a fine branch, the number of rows reached up to 15. The large dispersion of the length of egg batches (10-47 mm) correlated with the great variety of eggs in them – from 34 to 297 (Table 1). In most cases (88.3%), the female moths started to lay eggs from the tip of the needle. The distance from the base of the needle to the beginning of the egg batches was between 0 and 180 mm. The majority (62.7%) of the batches were clustered around the average value (87.3±37.9 mm) in a diapason of 60-120 mm (Fig. 2). The average survival of T. pityocampa in egg stage was 48% (Fig. 3). There was a significant deviation from maximal value of hatched larvae in Skidia (55.1%) and the minimal one in Thimonia (37%). The proportion of eggs destroyed by parasitoids and predators varied from 37.7% (Skidia) to 54.3% 2 GEORGIEVA ET AL. (Thimonia), with an average of 43.8% (Fig. 3). However, the impact of predators was very low – between 0% (Panagia) and 0.13% (Skidia), with an average of 0.07%. Table 1. Biometric indices of egg batches of T. pityocampa. Site Parameters Total/ Skidia Thimonia Alyki Panagia Average Total number of egg batches 48 24 22 2 96 Total number of eggs 10280 5374 4324 413 20391 Mean eggs per egg batches ± SD 214.2±48.4 223.9±43.1 196.5±65.7 206.5±54.5 212.4±51.9 Range of eggs per egg batches 65-283 67-297 34-292 168-245 34-297 Average length of needles wrapped by an egg batch, mm 152.0±26.7 159.3±27.5 142.6±22.9 84 151.1±27.2 ± SD Range of length of needles wrapped by an egg batch, mm 85-210 110-210 110-200 84 84-210 Number of needles wrapped by egg batches - on one needle 2 (4.2%) 1 (4.2%) 2 (9.1%) - 5 (5.2%) - on two needles 43 (89.6%) 19 (79.2%) 18 (81.8%) 1 (50.0%) 81 (84.4%) - on three needles 1 (2.1%) 2 (8.3%) 1 (4.5%) - 4 (4.2%) - on four needles 1 (2.11%) 2 (8.3%) 1 (4.6%) - 4 (4.2%) - on twig 1 (2.0%) - - 1 (50.0%) 2 (2.0%) Orientation of scales on egg batches, number - from base to tip needles 44 (93.6%) 19 (79.2%) 20 (90.9%) 0 (0%) 83 (88.3%) - from tip to base needles 3 (6.4%) 5 (20.8%) 2 (9.1%) 1 (100%) 11 (11.7%) Average length of egg batches, mm ± SD 31.4±7.1 31.4±6.4 29.3±7.4 26 30.9±7.1 Range of length of egg batches, mm 10-47 10-44 12-42 16-36 10-47 Average diameter of egg batches, mm ± SD 3.3±0.3 3.4±0.4 3.4±0.5 3.4±0.4 Range of diameter of egg batches, mm; 3.0-4.9 3.0-4.4 3.0-5 3.1-5.2 3.0-5.2 Distance of egg batches to base of needles, mm ± SD 95.1±32.5 81.8±47.8 77.9±35.9 87.3±37.9 Range of distance of egg batches to base of needles, mm; 3-155 5-180 0-138 24 0-180 Average number of egg rows per batch ± SD 7.5±1.2 7.8±1.4 7.9±1.3 7.7±1.5 Range of number of egg rows per batch 6-13 6-11 6-11 7-15 6-15 Figure 1.