Nematinae

The Nematinae are a large and diverse group, especially in habits and host plants. It is the dominant sawfly group in the arctic and subarctic regions of the world where they comprise nearly the entire sawfly fauna. Their abundance decreases rapidly southward and only a few species extend into Mexico. Only two species, both Pristiphora, are known from South America. Larval habits range from free leaf feeders to gall formers, others are leaf edge rollers, leaf miners, and some live and feed inside the fruits of rosaceous plants. The taxonomy of many groups is imperfectly known and few have been recently studied. Because of their abundance in the arctic region, many represent holarctic species, and a worker is met with the major obstacle of having to become familiar with the innumerable forms described from Eurasia. Variation is another factor since the extreme arctic climate may influence major morphological and color differences within species. For example, females of Amauronematus abnormis (Holmgren) are normally brachypterous, but females with normal wings also exist. Some of the gall forming groups apparently contain species complexes where there are practically no adequate morphological characters for species separation and where identity may have to be based on specific host records and accompanying biological information. Extensive field work and knowledge of the world fauna will be essential to the study of most groups, and such facilities are not available to most taxonomists.