Stem borer (Hymenoptera: Cephidae) in Ribes

Record Details

Record no.:	0444
Feeding guild:	Stem borer
Taxonomy:	Hymenoptera: Cephidae: Janus integer
Stages observed:	trace, egg, larva
Hosts in Ribes:	undetermined R. sp. (gooseberry)

The adult female sawfly lays an egg in the stem of a spring shoot of the host and then uses her ovipositor to make several cuts around the circumference of the shoot above the oviposition site, girdling the shoot. The top of the shoot then breaks off or wilts. The larva, which possesses a prong on the posterior end (the "suranal process" in Yuasa (1922)), tunnels downward through the remaining portion of the stem of the shoot, and spends the summer enlarging its gallery in the pith of the stem. It passes the winter as a mature larva in the stem, and adults emerge in spring. The life history of this species was described in detail by Slingerland (1897).

Featured Images

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Image #: 444-01 Ribes shoot with upper part broken off at the point where the stem was girdled by an adult sawfly. (Photo date: June 7, 2022)

Image #: 444-02 Another affected shoot. (Photo date: June 14, 2023)

Image #: 444-03 A third affected shoot, in this case with the upper portion having completely fallen off of the plant. (Photo date: June 14, 2023)

Image #: 444-04 A fourth affected shoot, playing host to an egg of Janus integer. (Photo date: June 17, 2022)

Image #: 444-05 Affected shoot, with arrow indicating the approximate location of an egg inside the stem.

Image #: 444-06 Affected shoot, with red dot indicating the approximate location of an egg inside the stem.

Image #: 444-07 Affected shoot, showing what appear to be cuts made by the adult female sawfly with her ovipositor.

Image #: 444-08 Affected shoot, showing what appear to be cuts made by the adult female sawfly with her ovipositor.

Image #: 444-09 Egg in dissected stem. (Photo date: June 17, 2022)

Image #: 444-10 Affected shoot, an estimated 10-15 days after being girdled by an adult female sawfly; the female's egg has hatched and the living portion of the shoot contains a young larva. (Photo date: June 21, 2023)

Image #: 444-11 Young larva inside stem of shoot from previous photo (0444-10). (Photo date: June 25, 2023)

Image #: 444-12 Young larva inside stem of shoot.

Image #: 444-13 Young larva. Length: 1.3mm.

Image #: 444-14 The larva spends the rest of its first growing season feeding and dwelling in the stem. Once full-grown, it overwinters in the stem, in preparation for pupating and emerging as an adult in the spring. This photo shows an overwintering stem inhabited by a mature larva. Note the truncated apical end of the stem, the result of the shoot tip having fallen off after being girdled by the adult female sawfly during the spring of the previous growing season. (Photo date: January 7, 2023)

Image #: 444-16 Top end of inhabited stem in winter. This stem contains a mature larva, dwelling in the lower portion of the stem that is not in view in this photo.

Image #: 444-17 Compacted frass in larval tunnel in dissected overwintering stem. (Photo date: January 7, 2023)

Image #: 444-18 Compacted frass in larval tunnel in dissected overwintering stem. (Photo date: January 7, 2023)

Image #: 444-19 Overwintering mature larva in dissected stem. (Photo date: January 7, 2023)

Image #: 444-20 Overwintering mature larva in dissected stem.

Image #: 444-22 Anterior end of larva in stem.

Image #: 444-23 Overwintering mature larva, lateral. (Photo date: January 7, 2023)

Image #: 444-26 Lateral view of abdominal segments of mature larva, showing texture of integument.

Image #: 444-27 Head of mature larva, ventral.

Image #: 444-28 Head of mature larva, front view.

Image #: 444-30 Mandible of mature larva.

Image #: 444-31 Rear view, posterior end of mature larva, showing "suranal process" (term from Yuasa (1922)).

Image #: 444-32 Lateral view, posterior end of mature larva, showing suranal process.

Image #: 444-33 Suranal process of mature larva in lateral view.

Image #: 444-34 Dorsal view, posterior end of mature larva, showing suranal process.

Image #: 444-35 Suranal process of mature larva in dorsal view.

Specimen Data for Images

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Field photos taken 06/07/22 (01), 06/14/23 (02-03), 06/21/23 (10), 01/07/23 (14-16); coll. 06/16/22, photos on 06/17/22 (04-09); coll. 06/21/23, photos on 06/25/23 (11-13); coll. 01/07/23, photos on 01/07/23-01/08/23 (14-35).

References

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Slingerland, M.V. 1897. The currant-stem girdler and the raspberry-cane maggot. Cornell University Agricultural Experiment Station, Bulletin 126 (February 1897), pp. 41-60.[return to in-text citation]
Yuasa, H. 1922. A classification of the larvae of the Tenthredinoidea. Illinois Biol. Monogr. 7(4):1-172.[return to in-text citation]

Page created: November 20, 2023. Last update: February 27, 2026