Stem borer (Hymenoptera: Cephidae) in Salix

Record Details

Record no.:	0476
Feeding guild:	Stem borer
Taxonomy:	Hymenoptera: Cephidae: cf. Janus abbreviatus
Stages observed:	trace, larva, pupa
Hosts in Salix:	S. nigra (black willow)

The larva tunnels in the stem of a shoot of the hostplant, and the tunnel behind the larva fills with frass. The upper part of the shoot may wilt conspicuously. Winter is passed in a chamber in the shoot and pupation happens there in spring, with adults emerging soon thereafter. For more information on the life history of this species, see, e.g., Middlekauff (1969), Ries (1937), and Solomon (1995).

Featured Images

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Image #: 476-15 Inhabited shoot, girdled by the sawfly, causing the shoot tip to die. (Photo date: April 28, 2023)

Image #: 476-16 Inhabited shoot with necrotic tip.

Image #: 476-17 Area of stem girdled by the sawfly. The whitish discolored areas on the stem (right of center) have been mined shallowly by Marmara sp. (Lepidoptera: Gracillariidae); this feeding is unrelated to the sawfly damage.

Image #: 476-18 Stem girdled in a spiral pattern.

Image #: 476-01 Wilted willow shoot shown in winter, long after the damage occurred during the previous growing season. (Photo date: January 10, 2023)

Image #: 476-02 Necrotic upper end of inhabited stem.

Image #: 476-03 The upper part of this inhabited stem has been girdled by the borer in a spiral pattern. A similar example is shown in Fig. 235F of Solomon (1995).

Image #: 476-04 Accumulated frass in stem tunnel. (Photo date: Jaunary 11, 2023)

Image #: 476-05 Larva overwintering in lower stem. (Photo date: January 12, 2023)

Image #: 476-12 Prong (the "suranal process" described in Yuasa (1922)) on posterior end of larva, in lateral view.

Image #: 476-13 Suranal process on posterior end of larva, in dorsal view.

Image #: 476-14 Pupa, formed in the stem. (Photo date: April 28, 2023)

Specimen Data for Images

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Field photo on 01/10/23 (01); coll. 01/10/23 & 01/12/23, photos of stem damage on 01/11/23 (02-04), photos of larva on 01/12/23 (05-13), pupa formed by 04/28/23, photo of pupa same day (14); coll. 06/28/21, field photo same day (15), additional photos on 07/02/21 (16-18). All specimens above from Iowa, USA.

References

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Middlekauff, W.W. 1969. The cephid stem borers of California (Hymenoptera: Cephidae). Bulletin of the California Insect Survey 2:1-19.[return to in-text citation]
Ries, D.T. 1937. A revision of the Nearctic Cephidae. Trans. Amer. Ent. Soc. 63:259-324.[return to in-text citation]
Solomon, J.D. 1995. Guide to insect borers in North American broadleaf trees and shrubs. USDA Forest Service Agriculture Handbook AH-706.[Note: As of December 2023, fig. 235F from this publication is available online, as image number 3056050 on the Forestry Images website at https://www.forestryimages.org/browse/detail.cfm?imgnum=3056050.][return to in-text citation]
Yuasa, H. 1922. A classification of the larvae of the Tenthredinoidea. Illinois Biol. Monogr. 7(4):1-172.

Page created: March 10, 2026. Last update: none