Diprion similis

Identification

Diprion similis is very similar to the sympatric European species D. pini, in both sexes. These two species are distinguished from all others by the versicolored propleurae. Both are discriminated by bicoloredbicolored:
having two colors, with the change between these colors being abrupt.
protibiae from D. jingyuanensis, D. koreanus, D. liuwanensis, D. nipponicus, and D. wenshanicus.

Female Diprion similis are distinguished from D. pini by the regularity of annular serration on gonapophyses VIII, and from all other Diprion spp. by versicolored propleuraepropleuron:
a sclerite of the prothorax ( = front-most thoracic segment) to which the foreleg articulates. Visible in profile and ventral views.
. Contrary to Viitasaari and Varama (1987)Viitasaari and Varama (1987):
Viitasaari M. and Varama M. 1987. Sahapistiäiset 4. Havupistiäiset (Diprionidae). [In Finnish.] Helsingen yliopisto. Maatalous ja metsäeläintieteen laitos. Julkaisuja 10: 79 pp., coloration of the scape and pedicel is not useful for distinguishing females of these species.

The male is distinguished from that of D. pini by distaldistal:
remote from the body.
infumation in the hindwing being faint, or more often absent, and the proximoventral corner of the valvicepsvalviceps:
the distal end of the penial sclerite. There is no explicit anatomical boundary between the valviceps and the remainder of the penial sclerite.
projecting lower than the distoventral corner. Diprion similis and D. pini are together distinguishable from all other Diprion spp. in the presence of occipital maculae.

Discrimination between D. pini and D. similis is far easier for larval specimens, at least in the final feeding instarinstar:
the stages of the sawfly larva, delimited by moulting events in which the larva sheds its exoskeleton and thus grows larger. The appearance of the larva changes dramatically throughout its growth from hatching to prepupa. The number of instars may differ according to sex.
and prepupaprepupa:
The final larval instar, which does not feed. Its appearance can differ somewhat from preceding instars.
. In D. similis, these stages are ventrally pale whitish to yellow, with this color on the dorsal side being mottled with black, white, and bright yellow (Davis et al. 2023aDavis et al. 2023a:
Davis JS, Glover AN, Everson KM, Coyle DR, Linnen CR. 2023a. Identification, biology, and management of conifer sawflies (Hymenoptera: Diprioninae) in eastern North America. Journal of Integrated Pest Management 14(1): 13; 1–16.).

Plant associations

In its native range, the introduced pine sawfly primarily attacks Scots pine (Pinus sylvestris); in North America, its preferred host is eastern white pine (Pinus strobus).

View full screen host table here

Distribution

Native to the Western Palearctic (Smith 1974Smith 1974:
Smith DR. 1974. Conifer sawflies, Diprionidae: key to North American genera, checklist of world species, and new species from Mexico (Hymenoptera). Proceedings of the Entomological Society of Washington 76(4): 409–418.), from France (Chevin and Savina 2016Chevin and Savina 2016:
Chevin H and Savina H. 2016. Contribution à l’inventaire des Hyménoptères Symphytes du département de Seine-et-Marne. Bulletin de la Société entomologique de France 121(2): 149-166.) and the Balkan Peninsula (Žikić et al. 2019Žikić et al. 2019:
Žikić V, Milošević MI, Stanković SS, Lazarević M, Lotfalizadeh H. 2019. 2019. Two new hymenopteran findings in Serbia: Diprion similis (Diprionidae) as host and its parasitoid, Monodontomerus dentipes (Torymidae). Acta Entomologica Serbica 24(2): 57–61.) eastward to Kurgan Oblast, Russian Federation (de Jong 2021de Jong 2021:
de Jong Y. 2021. Fauna Europaea Consortium. Accessed June 2, 2025.). Established in eastern North America and in the Pacific Northwest of the United States (Davis et al. 2023aDavis et al. 2023a:
Davis JS, Glover AN, Everson KM, Coyle DR, Linnen CR. 2023a. Identification, biology, and management of conifer sawflies (Hymenoptera: Diprioninae) in eastern North America. Journal of Integrated Pest Management 14(1): 13; 1–16.).

Natural enemies

The wasp Exenterus amictorius (Hymenoptera: Ichneumonoidea: Ichneumonidae: Tryphoninae) is a common parasitoid of the larva of the introduced pine sawfly (Weber 1977Weber 1977:
Weber BC. 1977. Parasitoids of the introduced pine sawfly, Diprion similis (Hymenoptera: Diprionidae), in Minnesota. The Canadian Entomologist 109(3): 359–364.). As in the common pine sawfly (Diprion pini), the larval stage of the introduced pine sawfly is also attacked by the true fly Drino inconspicuoides (Diptera: Oestroidea: Tachinidae) (Hardy 1936Hardy 1936:
Hardy JE. 1936. Natural control of Diprion similis, Htg., in Poland during 1936. Bulletin of Entomological Research 30(2): 237–246.).

Meanwhile, the wasp Monodontomerus dentipes (Chalcidoidea: Torymidae) and various wasps in the Cryptinae (Ichneumonoidea: Ichneumonidae) are parasitoids of the prepupaprepupa:
The final larval instar, which does not feed. Its appearance can differ somewhat from preceding instars.
of the introduced pine sawfly, attacking this stage within the cocoon (Hardy 1936Hardy 1936:
Hardy JE. 1936. Natural control of Diprion similis, Htg., in Poland during 1936. Bulletin of Entomological Research 30(2): 237–246., Žikić et al. 2019Žikić et al. 2019:
Žikić V, Milošević MI, Stanković SS, Lazarević M, Lotfalizadeh H. 2019. 2019. Two new hymenopteran findings in Serbia: Diprion similis (Diprionidae) as host and its parasitoid, Monodontomerus dentipes (Torymidae). Acta Entomologica Serbica 24(2): 57–61.). 

Taxonomy

Basionymbasionym:
the original combination of a species name, consisting of the genus name and a specific epithet.
: Lophyrus simile Hartig, 1836

Junior synonyms: Diprion eremita (Thomson, 1871); Diprion simile var. atroscutellatum Enslin, 1916; Diprion simile var. claristernis Enslin, 1916

Obsolete or incorrect combinations: Diprion simile, Lophyrus similis, Neodiprion simile, Neodiprion similis, Tenthredo (Lophyrus) similis

The introduced pine sawfly has sometimes been treated as a synonym of D. pini (Reh 1913Reh 1913:
Reh L. 1913. Die tierischen Feinde (Vol. 3). Paul Parey Zeitschriftenverlag: Singhofen.), but most authors from Baer (1906)Baer (1906):
Baer W. 1906. Lophyrus similis Hart. Naturwissenschaftliche Zeitschrift für Land- und Forstwissenschaft 4(2): 84–92. onwards consider them to be separate. As Hardy (1936, p. 237) put it, their synonymy is "hardly tenable" given the consistent and pronounced phenotypic differences seen in the larvae.