The Stem Sawflies of Florida

The Cephidae are called stem sawflies because of the habits of the larvae which bore and feed in berry canes, stems or twigs of various shrubs, or in grass stems. The North American species all belong to the subfamily Cephinae which contains two tribes, Cephini and Hartigiini (Ries 193 7). Species of the tribe Cephini can be serious pests of grains. There are three species of Cephini of European origin in the eastern United States: the wheat stem sawfly, Cephus cinctus Norton; the European wheat stem sawfly, Cephus pygmaeus (Linnaeus); and the black grain stem sawfly, Trachelus tabidus (Fabricius). These European species are not yet in Florida, but some species, such as the wheat stem sawfly, are actively dispersing. The wheat stem sawfly dispersed into northern Georgia about 1990. Apparently there is a critical time period when grasses or grains can be attacked and it is hypothesized that no economic species of grasses will be affected in the eastern United States since they are not suitable during the period of oviposition.

The Florida species of Cephidae all belong to the tribe Hartigiini. The only recorded species in Florida is Hartigia trimaculata (Say), a pest of blackberries and roses (Smith 1986). Two additional species are newly recorded here for Florida. These are Janus abbreviatus (Say), the willow shoot sawfly (first collected in 1977), and Janus integer (Norton), the currant stem girdler (first collected in 1995). None of the Florida species occurs in large enough numbers to cause any significant economic damage, but outbreaks of any one of these species could occur in the future.

The family Cephidae is easy to identify since it is morphologically intermediate between the Hymenoptera suborders Symphyta and Aculeata. The first abdominal segment is not fused with the thorax in Cephidae distinguishing them from the Aculeata which have the first abdominal segment incorporated into the thorax as the propodeum. The cephids lack the metanotal cencri (pair of hard, opaque, rough areas) found in all other families of Symphyta. The Florida members of this family range in size from about 8 to 20 mm and have the bodies laterally compressed (Figs. 1-3).