Phylloecus

Taxonomy

Family: Cephidae
Family common name: stem sawflies
Subfamily: Cephinae
Genus: Phylloecus Newman 1838
Subgenera: none

Background

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).

Diversity

There are 32 described species worldwide, restricted to the Northern Hemisphere. Five species are present in North America (Liston and Prous 2014, Taeger et al. 2018).

A key to North American species of Phylloecus (as Hartigia) is included in Smith 1986a.

Diagnostic characteristics

May be confused with

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).

Exotic pest species of concern

none

Host associations

In North America, the known hosts are the Rosaceae genera Rosa (rose) and Rubus, including blackberry, raspberry, and boysenberry (Ries 1937, Smith 1986a).

Life history

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).

Larvae generally undergo a period of diapause, over winter, then pupate inside the hollow stem. The adult chews or pushes its way out of the stub and emerges. This genus is univoltine (Smith 1986a).

Two North American species, P. fasciatus and P. trimaculatus, are pests of caneberry crops (Ries 1937).

Distribution

World: Phylloecus is Holarctic, with species recorded from Europe to Japan and in North America (Taeger et al. 2010).

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).

Map data from: GBIF.org (26 June 2019) GBIF Occurrence Download Hartigia and GBIF.org (30 January 2020) GBIF Occurrence Download Phylloecus

Details about data used for maps can be found here.

Phylloecus fasciatus female lateral habitus; photo by J. Orr, WSDA

Phylloecus fasciatus female lateral habitus; photo by J. Orr, WSDA

Phylloecus fasciatus female dorsal habitus; photo by J. Orr, WSDA

Phylloecus fasciatus female dorsal habitus; photo by J. Orr, WSDA

Phylloecus fasciatus female face; photo by J. Orr, WSDA

Phylloecus fasciatus female face; photo by J. Orr, WSDA

Phylloecus fasciatus male lateral habitus; photo by J. Orr, WSDA

Phylloecus fasciatus male lateral habitus; photo by J. Orr, WSDA

Phylloecus fasciatus male dorsal habitus; photo by J. Orr, WSDA

Phylloecus fasciatus male dorsal habitus; photo by J. Orr, WSDA

Phylloecus fasciatus male face; photo by J. Orr, WSDA

Phylloecus fasciatus male face; photo by J. Orr, WSDA

Phylloecus fasciatus wings, photo by J. Orr, WSDA

Phylloecus fasciatus wings, photo by J. Orr, WSDA

Phylloecus fasciatus hind tibia; photo by J. Orr, WSDA

Phylloecus fasciatus hind tibia; photo by J. Orr, WSDA