Family common name: stem sawflies
Genus: Phylloecus Newman 1838
The Cephidae are commonly known as “stem sawflies” because larvae feed and live within the stems of small herbaceous and woody plants. Many are considered pests since this feeding behavior can damage or kill the host plant (Shanower and Hoelmer 2004).
Stem sawflies of the genus Phylloecus are generally black and slender, with slightly laterally compressed cylindrical bodies. They are the largest Cephidae of North America and can be up to 20 mm in length (Smith 1986a). Sexes are best distinguished by the presence or absence of the ovipositor (Ries 1937).
A key to North American species of Phylloecus (as Hartigia) is included in Smith 1986a.
Species of Phylloecus are often confused with other Cephidae, especially with similar genus, Janus. It is distinguished from Caenocephus by the presence of the preapical hind-tibia spurs and presence of vein 3r-m in the hind wing. It can be distinguished from Janus by the lack of a basal lobe on the tarsal claws and the presence of only a single preapical spur on hind tibia (Smith 1986a).
Female Phylloecus oviposit into stems of shrubs (Middlekauff 1969). The larva feeds spirally on the cambium and pith just below the bark, moving upwards towards the growth tip (Alston et al. 2009). Larvae are creamy white and grub-like in appearance. They lack abdominal prolegs, and thoracic legs are vestigial. Cephidae larvae possess a tubular dorsal horn on the posterior end of the body (Middlekauff 1969). As the larva feeds, it uses this horn to pack frass in the gallery behind it. At the tip of the branch, the larvae turn around and burrow deeper into the now hollow cane (Alston et al. 2009). Some of the species are documented girdling the stem above the burrow, which can cause the cane to die and fall off (Smith 1986a).
Two North American species, P. fasciatus and P. trimaculatus, are pests of caneberry crops (Ries 1937).
North America: Phylloecus range throughout North America in southern Canada and the continental United States. Two species are restricted to the Pacific Northwest region of the United States. A single species occurs in Mexico, in the state of Chiapas (Smith 1986a).
Details about data used for maps can be found here.