Diversity and flight activity of Staphylinidae in a citrus orchard of the Catania Plain (Sicily)

Abstract

The present study aims to investigate the diversity and flight activity of Staphylinidae in a citrus orchard of the Catania Plain (Sicily) using different sampling methods (car-net, window traps and pit-fall traps). The study looks at the complex of flying rove beetles with the aim of defining preliminarily the faunistic and zoogeographical structure of this family in the study area. A second aim of the study is to investigate, using window-traps and pit-fall traps, the spatial distribution of flying staphylinids inside the orchard and in adjacent habitats. The use of window traps and car-net allowed to analyse the monthly and daily flight activity of staphylinids and to analyse the flight circadian rhythm and its seasonal variation. Monitoring of wind and temperature also allowed to evaluate the effects these environmental factors on the flight activity. 170 taxa (species, subspecies and 20 morphospecies) of Coleoptera Staphylinidae were collected. Most of the species are eurytopic species or related to substeppic or steppic environments, usually saprophyles with broad ecological valence. 5 species (Pella leonhardi, Pronomaea sicula, Quedius caelebs, Tasgius globulifer evitendus and Tasgius pedator siculus) are endemics to Sicily, 1 species (Oxypoda flavissima) is new for Italian fauna, 11 species (Acrotona muscorum, Amischa decipiens, Amischa forcipata, Atheta testaceipes, Carpelimus fuliginosus, Dacrila pruinosa, Lithocharis nigriceps, Micropeplus porcatus, Neobisnius lathrobioides, Outachyusa raptoria, Pycnota paradoxa e Trichiusa immigrata) are new for Sicilian fauna. The chorological spectrum is coherent with the environment where the research took place: a large orchard plain characterized by prolonged summer aridity. The results of the window trap sampling show significant differences in the abundance of the flying species between open areas inside the orchard characterized by herbaceous vegetation (Track) and the inside of the parcels of citrus grove (Citrus). On the other hand the Spearman rank correlation analysis demonstrates that the faunistic structures of this stations are similar. Comparison between sampling with pit-fall traps and with windows traps one shows that these two sampling methods basically differ by the taxa captures frequencies, in addition to the complete absence of Ocypus o. olens in the window traps. The occurrence of the maximum frequency of catches in the window traps in the spring (often in contrast with car-net data) suggests that in this period blooming and fruits marcescence processes are an attractive stimulus which causes an increase of flight activity. Hourly sampling with car-net highlighted, in the most abundant species, that flight has a circadian rhythm characterized by morning and afternoon peaks with a break or a decrease at midday. The beginning of flight activity coincides with dawn in summer period in Gabronthus maritimus and in Alaeocharinae and Oxytelinae (not examined at species level). Flight activity s end takes usually place at sunset or twilight. Flight activity after dusk up to an hour after sunset has been detected in the Paederinae Scopaeus debilis, Hypomedon debilicornis, Astenus b. bimaculatus and Astenus pallidulus. There are also seasonal variations of the distance of morning and afternoon peaks from dawn and sunset: in winter they are far away from dawn and from sunset, in spring the afternoon peak gets closer to sunset, in summer morning peak moves closer to dawn and the afternoon one overlaps sunset, in autumn this two peaks move away from dawn and from sunset again. From autumn to spring the beginning of flight activity is conditioned by temperature. High temperature seems to cause the extension of the midday break which in summer extends until mid-afternoon. Wind is also an environmental factor which influences flight: in several species wind s high speeds reduce flight s activities. However, afternoon peaks also occur in highly windy day.