Stem stumps

Synopsis

This page collects images of stem stumps created by borer larvae that I encountered in the survey. At least seven different insect families are represented, spread across all four major orders. Click on "Images" in the page navigation menu (at left or above) to jump to the Images section, or use the list of links below for finer-grained navigation to the individual images. I have also summarized some other instances of stemp stump-forming larvae reported in the entomological literature ("Related Reports", below).

Images

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Image #: 1 *Hellinsia glenni* (Lepidoptera: Pterophoridae) in *Solidago* (0517). L-R: Stem stump; stump recently cut by larva, with upper portion of plant freshly lodged; cut end of stump, showing beveled edge and frass plug; top panel: larva from stump; bottom panel: reared adult. (Top)

Image #: 2 *Hellinsia glenni* (Lepidoptera: Pterophoridae) in *Symphyotrichum* (0559). L-R: Stem stump; frass inside stump; top panel: cut end of stump, during overwintering, showing frass plug; bottom panel: cut end of stump, after adult's emergence, showing open end; larva in stump; reared adult. (Top)

Image #: 3 Lepidoptera: cf. Tortricidae in *Rudbeckia hirta* (0702). L-R: Stem stump, with lodged upper portion of plant lying nearby; lodged upper portion of plant, showing slender lizard beetle larva (Coleoptera: Erotylidae: *Acropteroxys gracilis*, denoted by black arrow) resting in its tunnel above densely packed frass, and cut end of stem at bottom; Lepidoptera larva's frass; larva in stem stump; larva. (Top)

Image #: 4 *Thrypticus* (Diptera: Dolichopodidae) in *Elymus* (0207). L-R: culm stump; interior of uppermost portion of stump, showing plug made of very fine-grained material; larva in stump; developing pupa; reared adult. (Top)

Image #: 5 *Thrypticus* (Diptera: Dolichopodidae) in *Setaria pumila* (0640). L-R: culm stump; detail, stump, backlit, with frass plug (denoted by the red bracket) visible through the outer wall of the culm; frass plug; larva in stump; pupal exuviae protruding from stump after adult's successful emergence; reared adult. (Top)

Image #: 6 *Thrypticus* (Diptera: Dolichopodidae) in *Muhlenbergia* (0341). L-R: culm stump; detail, top of culm stump, showing frass plug and barely attached base of lodged upper portion of plant; larva in stump; section of stump interior, showing feeding debris and larva's posterior end; larva. (Top)

Image #: 7 *Oberea tripunctata* (Coleoptera: Cerambycidae) in *Ageratina altissima* (0019). L-R: Stem stump, very freshly cut and not yet plugged with frass; top of stump after larva has plugged it with frass (note both coarse shavings and fine-grained material); pupa from stump; reared adult, dorsal; same, lateral. (Top)

Image #: 8 Mordellidae (Coleoptera) in *Anemone cylindrica / virginiana* (thimbleweed) (0057). L-R: stem stump in winter, with lodged upper portion of plant lying nearby; top of stump, showing thin plug of frass and smooth-walled tunnel; larva; stump after adult's successful emergence, showing exit hole; reared adult. (Top)

Image #: 9 Mordellidae (Coleoptera) in *Symphyotrichum* (0540). L-R: stem stump; upper portion of stump, showing frass plug in cut end; ~10mm plug in top of stump, composed of extremely fine-grained frass; pupa in stump; reared adult. (Top)

Image #: 10 *Caulocampus* cf. *acericaulis* (Hymenoptera: Tenthredinidae) in *Acer saccharum* (0006). L-R: petiole stump; upper portion of stump, backlit, with frass plug and larva's tunnel partly filled with frass visible through outer wall of petiole; frass inside tunneled petiole; larva in stump; larva. (Top)

Related Reports

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The following table provides some additional examples of larvae from around the world that construct stem stumps in herbaceous tissue, drawn from the entomological literature. This list is not intended to be comprehensive.

Additional instances of larvae forming stumps in herbaceous stems and stemlike structures
Order	Family	Lower taxon	Host plant	Description	Reference
Coleoptera	Cerambycidae	Dectes sayi	Ambrosia artemisiifolia (Asteraceae)	Stem girdled "5.0-8.0 cm above ground level" and plugged with "2.5-7.5 cm...of tightly packed powdery frass" (p. 301); plant above girdled area lodges and larva overwinters in root at or below ground level	Piper (1978)
Coleoptera	Cerambycidae	Dectes texanus	Glycine max (Fabaceae)	As stem dries near season's end, "larvae tunnel down to the base of the plant, girdle the inside of the stem about 5 cm (2 in) above the soil line and plug the tunnel with frass" (p. 4); this is followed by "subsequent late season lodging" (p. 5) of some affected plants. "Lodged stems with a smooth concave break near soil level are an indicator of Dectes stem borer larval girdling (Campbell 1980)" (p. 7).	Rystrom (2015)
Coleoptera	Curculionidae	Lixus macer	Helianthus grosseserratus (Asteraceae)	"Late in October, pieces of these stems, from one and a half to three feet long, were found lying about on the ground, evidently having been gnawed off from within, excepting the thin, outer bark, which had apparently been broken by the wind. These pieces contained [an apparent L. macer] larva" (pp. 11-12). So "stem logs" are produced, rather than stem stumps? See discussion in entry for L. concavus, below.	Webster (1889)
Coleoptera	Curculionidae	Lixus concavus	Helianthus sp. (Asteraceae)	"When full grown, the larvae girdle the stems from within, at irregular intervals...only the thin outer bark is left intact, to be broken off by the winds...the larva [plugs the opening] with fibrous matter, taken from within the stem...[the girdled stem] sections are not to be found scattered about on the ground much before October." (pp 15-16). These accounts of "stem logs" made by L. macer (see previous entry in this table) and L. concavus do not specifically mention stumps still anchored to the ground. However, Webster writes, "we have taken thirteen full grown larvae from a section of Helianthus only about as many inches in length" (p. 13), and with so many larvae per stem, it seems likely some end up dwelling near ground level and girdling the plant above that point. These entries are listed tentatively.	Webster (1889)
Coleoptera	Mordellidae	Mordellistena ?nubila	Tridens flavus (as Triodia cuprea) (Poaceae)	"At from one to two inches above the ground the stem is almost cut through so that it is frequently broken off by the wind." (p. 321)	Riley (1892) (POWO 2026 for grass taxonomy)
Hymenoptera	Cephidae	Cephus spp., including C. cinctus, C. pygmaeus, and C. tabidus	Various cultivated grains, incl. wheat, barley, rye, oats; numerous wild grasses (Poaceae) (see Wallace & McNeal for full host list)	Larvae "girdle the stem at the base when preparing for hibernation. Girdled stems break off and lodge or fall to the ground (fig. 2)" (p. 5). Fig. 1 in this publication (see reproduction below this table) suggests the three Cephus species may be differentiated in part by the appearance of the tops of the stem stumps they produce.	Wallace and McNeal (1966)
Lepidoptera	Crambidae, Noctuidae	Busseola fusca (Noctuidae); Chilo (Crambidae) and Sesamia (Noctuidae) spp.	Zea mays; Sorghum (Poaceae)	Larval feeding of B. fusca may cause "lodging and breakage" in Z. mays (Haile, p. 55). Chilo and Sesamia spp. may cause similar damage to corn and/or sorghum, possibly in the same agricultural fields. Older larvae of B. fusca and C. zonellus tunnel "into the stem both vertically downwards and horizontally across. It is this latter activity which gives a characteristic line..." [Text goes to next page, which is unavailable to JvdL, but this seems to suggest the stem breakage is something more than an incidental result of vertical tunneling.] (Duerden, p. 105)	Chernoh (2014); Duerden (1953); Haile (2024)
Lepidoptera	Noctuidae	Ostrinia nubilalis	Zea mays (Poaceae)	"Boring damage may weaken the plant, causing stalk breakage"..."Second generation borer attack may result in stalk or tassel breakage". Is the stalk breakage deliberate or incidental on the part of the larva?	Purdue University College of Agriculture (2026)
Lepidoptera	Sesiidae	Chamaesphecia nigrifrons	Hypericum spp. (Hypericaceae), incl. H. perforatum, H. hirsutum, H. maculatum, and H. tetrapterum	Stem is cut "very close to the ground, or as high as 15 cm or more" above ground in autumn, and capped with a "dome-shaped plug made of small plant fragments and silk" (p. 76). Upper portion of plant breaks off btwn. autumn & early spring, often with help of winter storms and snow. Mature pupa breaks through plug and protrudes from top of stump upon adult's emergence.	Garrevoet et al. (2019)

a scene of wheat plants with some stems lodged, and a cutaway of a sawfly larva in a wheat culm — *Cephus* (Hymenoptera: Cephidae) in wheat. Left: several wheat plants, some with with lodged stems; note the very short stem stumps at the bases of certain broken stems. Right: a larva in a stem stump, with a plug of frass capping the stump. Adapted from Davis et al. (1950), a public domain work in accordance with 17 U.S.C. § 105.

C. pygmaeus stem stump top is rougher than the other two; pygmaeus and tabidus larvae have a shorter terminal process than cinctus and the tabidus process is upturned — Larvae and stem stump tops of *Cephus* spp. L-R: *C. cinctus*; *C. pygmaeus*; *C. tabidus*. Adapted from Wallace and McNeal (1966), a public domain work in accordance with 17 U.S.C. § 105.

References

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Chernoh, E. 2014. Maize stalk borers. Africa Soil Health Consortium and Plantwise factsheet. Retrieved September 14, 2026 from https://www.cabidigitallibrary.org/doi/pdf/10.5555/20203114212. [return to in-text citation]
Duerden, J.C. 1953. Stem borers of cereal crops at Kongwa, Tanganyika, 1950-52. The East African Agricultural Journal 19(2): 105-119.[return to in-text citation]
Davis, E.G., Callenbach, J.A., and J.A. Munro. 1950. The wheat stem sawfly and its control. United States Department of Agriculture Bureau of Entomology and Plant Quarantine. 10 pp.[return to in-text citation]
Garrevoet, T., Goossens, R., and R. Meert. 2019. Chamaesphecia nigrifrons (Lepidoptera: Sesiidae), een nieuwe wespvlindersoort voor België. Phegea 47(3): 74-79.[return to in-text citation]
Haile, A. 2024. Damage and insecticidal control of stem borer (Busseola fusca L; Lepidoptera: Noctuidae) on maize in Halhal Begoss. Journal of Agriculture and Ecology 19: 55-58.[return to in-text citation]
Piper, G.L. 1978. Biology and immature stages of Dectes sayi Dillon and Dillon (Coleoptera: Cerambycidae). The Coleopterists Bulletin 32(4): 299-306. http://www.biodiversitylibrary.org/page/58743305 [return to in-text citation]
POWO. 2026. Triodia cuprea J.Jacq. In Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet. Retrieved September 14, 2026 from https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:1026384-2.[return to in-text citation]
Purdue University College of Agriculture. 2026. European corn borers (corn). Field Crops IPM factsheet. Retrieved September 14, 2026 from https://ag.purdue.edu/department/entm/extension/field-crops-ipm/corn/european-corn-borers.html.[return to in-text citation]
Riley, C.V. 1892. Coleopterous larvae with so-called dorsal prolegs. Proceedings of the Entomological Society of Washington 2(3): 319-324.[return to in-text citation]
Rystrom, Z.D. 2015. Seasonal activity and sampling methods for the Dectes stem borer, Dectes texanus Leconte, in Nebraska soybeans. M.S. thesis, University of Nebraska.[return to in-text citation]
Wallace, L.E. and F.H. McNeal. 1966. Stem sawflies of economic importance in grain crops in the United States. U.S. Department of Agriculture Technical Bulletin 1350. 50 pp.[return to in-text citation][return to in-text citation]
Webster, F.M. 1889. Some studies of the development of Lixus concavus, Say, and L. macer, Leconte. Entomologica Americana 5(1): 11-16. Retrieved September 15, 2026 from http://www.biodiversitylibrary.org/page/11422296.[return to in-text citation][return to in-text citation]

Page created: September 7, 2026. Last update: September 12, 2026