Biogeographical remarks on sawflies (Hymenoptera Symphyta) of the South-Eastern Alps

Abstract

BIOGEOGFIAPHIA — val. XIII — 1987 Biogeografia delle Alpi Sud-Orientali Biogeographical remarks on sawflies (Hymemoptem Sympbyta) of the South—Eastern . . Alps(*q). LUIGI MASUTTI Istzfitto di Entomologia zzgraria - Um'ver:z'tI2 di Padova SUMMARY Previous biogeographical considerations on the sawflies of forest and mountain habitats of Friuli draw a matter for further developments from the results of subsequent faunistic investigations. As for the species of high altitude biocoenoses, it is important to note the species attached to dwarf shrubs and herbaceous vegetation. Some elements have a circumboreal distribution, a few others are boreo-alpine (Empria zzlpimz Benson, Prz‘:tz'p/aora rtaudirzgeri (Ruthe), Porztzmia reticzdzztzze Malaise) or are still considered endemic to the Alps (Doleru: frz'gz'a'z/.r Benson, Nepiorzema /aelzzetzkwm Benson). The new findings increase the knowledge on the distribution of the species depending on forest trees, above all on conifers. The complex linked to the spruce is particularly numerous and includes, among other things, Cap/Jalczkz altzr/7aIzz'c:z eurapaea Benes and Gilpitzia /aercirziae (Hartig) at Tarvisio. The small but remarkable group of sawflies living on the mountain pine now shows more definite characteristics, Also the composite complex of species usually colonizing sylvan habitats, whose development howev- er does not depend on vegetation of trees or shrubs, seems more varied. Among the sawflies captured on grassy slopes of the Julian PreAlps, Tent/Jretlo pa-opiizqzza Klug and Mrzcrop/Jya teuzami (Panzer), rare and mostly distributed in southern and eastern mediterranean regions, are of importance. It is common knowledge that the development of sawflies depends, whith rare exceptions, on vegetable food. For the most part it is a matter of a well directed choice of host plants as well as of their exploitable organs. Thus, the geographic distribution of sawflies is based on the range of the botanical host species, on the ecological requirements of every single member of the suborder Symp/yyzfa and on the passive dispersal through human carriers. Indeed, the presence of host plants is not, in itself, a determining factor. According to Benson (1950), one of the most important reasons for the im- perfect overlap of ranges of each sawfly and its food—plants is linked to the scarce ability of adult sawflies to fly any great distance or to survive after long flights; physiological requirements and tolerances in terms of temper- ature and, above all, humidity are also of importance. In some environments, the non-coincidence of both an available substratum (flowers, fruit, shoots (*) This research was supported in part by the National Research Council of Italy (C,N.R.) (Grant n° 85.01568.06). 755