SAWFLIES (Hymenoptera: Symphyta)
Henri Goulet
INCREASE IN ABUNDANCE AND RANGES
All of the species recorded with expanding ranges and greater populations were introduced in the past 20 years in our region and they are still spreading. In Pamphiliidae, Acantholyda erythrocephala (Linnaeus) invaded in our region from the Montreal area. It is a common pest on pines, especially on stressed plants though lately they were recorded from mature mixed forests (my observations and those of B. Lyons). In Cimbicidae, Zaeraea fasciata Jurine, first recorded in Montreal, has been found also near Ottawa. The species is still uncommon. In Argidae, Arge ochropa (Gmelin), first recorded from southern Ontario, is known as far east as Montreal. It is a significant pest of cultivated roses. In the Blennocampinae of the Tenthredinidae, Halidamia affinis (Fallén), known from United States and southernmost Ontario, and is now recorded from the Ottawa region. This species is spreading north and eastward, and does not play a significant economic role. In the Heterarthrinae of the Tenthredinidae, Scolioneura betuleti (Zaddach), was first recorded from the vicinity of Toronto. This leaf miner is established and spreading in southern Ontario. In the Nematinae of the Tenthredinidae, Hoplocampa testudinea (Klug), invaded from southern Quebec, is recorded from Quebec City to west of Ottawa, and is still spreading westward. This species is an important pest of apples. Pristiphora denudata Konow, introduced on the Pacific coast, was recorded from Montreal. It is not known if it has become established. The larval host of this species is Rubus. In the Selandriinae of the Tenthredinidae, Dolerus nitens Zaddach, first recorded from Illinois and Montreal region in the early 1960's, is an extremely common species in pastures and lawns of our region. This species is assumed to have displaced the closely related D. unicolor (Beauvois). D. unicolor is now a rare species. Another species, Heptamelus ochroleucus (Stephens), known previously from the Pacific coast forests near Vancouver and Victoria, and near Washington D.C., was recently discovered in southernmost Quebec. This species is uncommon and associated with ferns.
In conclusion, the general trends of population changes are that most native species have maintained normal population levels while some crashed without any improvement, and that many introduced species are spreading with marked population increases. Most introduced species are affecting negatively our economy and sometimes our native fauna. There is a positive note in that three introduced species have been brought under control.