Cladius pectinicornis

(Geoffroy, 1785)

bristly rose sawfly

Cladius pectinicornis is a Palearctic whose larvae are known as bristly rose slugs, significant pests of cultivated roses. The small -like exhibit striking in structure, with males bearing pectinate (comb-like) antennae. Larvae skeletonize rose leaves by feeding on tissue between vascular bundles, and can cause severe defoliation when abundant. The has been introduced to North America, where it occurs on both coasts and ranges from Nova Scotia to British Columbia.

2021 11 06 Cladius pectinicornis by Slimguy. Used under a CC BY 4.0 license.

2023 06 10 Cladius pectinicornis Oviposition by Ralf Huber. Used under a CC BY-SA 4.0 license.

Cladius pectinicornis (Tenthredinidae) - (male imago), Arnhem, the Netherlands - 2 by

This image is created by user B. Schoenmakers at Waarneming.nl, a source of nature observations in the Netherlands.
. Used under a CC BY 3.0 license.

Pronunciation

How to pronounce Cladius pectinicornis: //ˈkleɪ.di.əs ˌpɛkˈtɪn.ɪˌkɔːr.nɪs//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from caterpillars by having six or more pairs of rather than five or fewer, and by lacking on prolegs. Separated from other rose-feeding by the bristly (setae-covered) appearance of larvae. identified by pectinate male and association with damaged rose foliage. Distinguished from Cladius difformis by subtle morphological differences; some authorities treat these as separate while others synonymize them.

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Habitat

Associated with cultivated roses in gardens and ornamental plantings. Larvae feed on rose leaves, particularly in sunny locations. found on or near plants. Overwinters as immatures in soil beneath rose plants.

Distribution

Native to the Palearctic region. Introduced to North America where it occurs on both the Atlantic and Pacific coasts, ranging from Nova Scotia to British Columbia. In the United States, primarily found in the northern third of the country except along coastlines where it extends farther south.

Seasonality

Larvae active spring through early summer, primarily May and June. One per year in most regions, though some may produce a second generation. emerge in spring when rose foliage returns. Overwinter as stages in soil.

Diet

Larvae feed on rose leaves (Rosa spp.), skeletonizing tissue between leaf . Also reported to feed on raspberries (Rubus spp.) and strawberries (Fragaria spp.). do not feed; their mouthparts are not adapted for chewing plant material.

Life Cycle

Winter is spent as stages in soil beneath plants. Development completes in spring when emerge and fly to rose leaves. Females use saw-like ovipositor to cut pockets in leaf midribs, depositing single . Eggs hatch and larvae proceed through five instars, with appetites increasing at each . Larvae skeletonize leaves, creating holes that enlarge as they grow. Mature larvae pupate in papery cocoons, often in soil or concealed locations. Some complete one per year; others may have a partial second generation.

Behavior

Larvae feed voraciously on rose foliage, with feeding intensity increasing through successive instars. When not feeding, larvae may curl on undersides of leaves or buds, providing camouflage. are active in sunlight, with males seeking females for mating. Females exhibit precise oviposition , cutting specific pockets in leaf midribs with their saw-like ovipositors.

Ecological Role

Herbivore that can significantly impact rose plant health through defoliation. Serves as prey for ground beetles and lightning (firefly) larvae. Contributes to nutrient cycling when abundant damage plant material.

Human Relevance

Significant pest of cultivated roses in gardens and commercial plantings. Heavy can make rose bushes appear burned or flamed by end of June. Control through hand-picking larvae, strong water sprays to dislodge them, or OMRI-listed including insecticidal soap and spinosad. Bacillus thuringiensis (Bt) is not effective against larvae. Requires careful timing to protect visiting roses.

Similar Taxa

Cladius difformisExtremely similar bristly rose ; treated as separate by some authorities (including David R. Smith) but synonymized by others. Occurs in similar range and on same . Separated by subtle morphological differences.
Endelomyia aethiops (roseslug sawfly)Another rose-feeding causing skeletonization damage, but larvae are smooth rather than bristly, and lack pectinate . Has only one per year.
Allantus cinctus (curled rose sawfly)Rose-feeding with different larval —curls tightly on leaf undersides when not feeding, causing marginal defoliation rather than skeletonization. lack pectinate .
True caterpillars (Lepidoptera larvae)Larvae resemble larvae but have five or fewer pairs of with (hooked structures) for gripping leaves, whereas sawfly larvae have six or more prolegs without crochets.

Misconceptions

Often mistaken for caterpillars (Lepidoptera larvae) due to similar appearance and feeding damage. Frequently confused with Cladius difformis; the two were long treated as the same , and some sources still synonymize them. The '' leads some to assume these are flies (Diptera), but they are actually -relatives in Hymenoptera. The name 'slug' in 'rose slug' refers to the larval form, not to any relationship with mollusks.