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Adults of Larinus obtusus Gyllenhal and Larinus minutus Gyllenhal in dorsal view. A, L. obtusus, male; B, L. obtusus, female; C, L. minutus, male; D, L. minutus, female.
Source publication
The morphology of two introduced knapweed feeders Larinus obtusus Gyllenhal, 1835 and Larinus minutus Gyllenhal, 1835 is investigated. The external and internal morphological characters are described for both sexes. The most promising discriminative characters including male and female terminal segments and genitalia structure are illustrated.
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... terminal segments and genitalia. Tergite 8 (Fig. 8C) subtrapeziodal, central part membranous. Sternite 8 nearly Y-shaped with short apodeme (Fig. 10A), lateral arms three times longer than apodeme, vertical arm short, narrow angularly and abruptly bent inward, posterior margin bearing a series of short hairs. Gonocoxites moderately sclerotized (Fig. 10B), hemisternite 1.50-1.65× as long as wide at widest part, base of stylus short, conical and slanted inward posteriorly, outer ...
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... terminal segments and genitalia. Tergite 8 (Fig. 8C) subtrapeziodal, central part membranous. Sternite 8 nearly Y-shaped with short apodeme (Fig. 10A), lateral arms three times longer than apodeme, vertical arm short, narrow angularly and abruptly bent inward, posterior margin bearing a series of short hairs. Gonocoxites moderately sclerotized (Fig. 10B), hemisternite 1.50-1.65× as long as wide at widest part, base of stylus short, conical and slanted inward posteriorly, outer margins bearing 2-3 short hairs; stylus subconical, slightly longer than base of stylus, slightly bent inward, bearing 3-4 very short hairs on tip. Spermatheca C-shaped, ramus slightly wider than nodulus, apex of ...
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... 1.50-1.65× as long as wide at widest part, base of stylus short, conical and slanted inward posteriorly, outer margins bearing 2-3 short hairs; stylus subconical, slightly longer than base of stylus, slightly bent inward, bearing 3-4 very short hairs on tip. Spermatheca C-shaped, ramus slightly wider than nodulus, apex of cornu obtuse (Fig. 10C). ...
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... subovate (Figs 1C-D), piceous; tibiae, tarsi, antenna and dorso-apical margin of prothorax always reddish brown. Body length 3.50-6.50 ...
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... terminal segments and genitalia. Tergite 8 trapeziodal (Fig. 8D), basal half membranous. Sternite 8 (Fig. 10D) Y-shaped, apodeme long, subequal in length to lateral arm, vertical arm wide, angularly and slightly bent inward, posterior margin bearing a few very short hairs. Gonocoxites (Fig. 10E) moderately sclerotized, elongate, hemisternite 2.50- 3.10× as long as wide at widest part, base of stylus very short, conical and strongly slanted ...
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... terminal segments and genitalia. Tergite 8 trapeziodal (Fig. 8D), basal half membranous. Sternite 8 (Fig. 10D) Y-shaped, apodeme long, subequal in length to lateral arm, vertical arm wide, angularly and slightly bent inward, posterior margin bearing a few very short hairs. Gonocoxites (Fig. 10E) moderately sclerotized, elongate, hemisternite 2.50- 3.10× as long as wide at widest part, base of stylus very short, conical and strongly slanted outward posteriorly, stylus conical, very short and slanted outward. Spermatheca C-shaped, ramus distinctly wider than nodulus, apex of cornu obtuse (Fig. 10F). premucro moderately developed ...
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... a few very short hairs. Gonocoxites (Fig. 10E) moderately sclerotized, elongate, hemisternite 2.50- 3.10× as long as wide at widest part, base of stylus very short, conical and strongly slanted outward posteriorly, stylus conical, very short and slanted outward. Spermatheca C-shaped, ramus distinctly wider than nodulus, apex of cornu obtuse (Fig. 10F). premucro moderately developed with a sharp denticle on female protibiae (Fig. 6D) tarsomere 3 1.30-1.40× as wide as tarsomere 2 in widest part, claws slightly unequal in length (Fig. 7C) tarsomere 3 1.20-1.33× as wide as tarsomere 2 in widest part; claws distinctly unequal in length (Fig. 7D) penis nearly parallel-sided, slightly ...
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... and angularly narrowed, with obtuse apex (Figs 9A-C) penis gradually narrowing from base to the upper corner of median orifice, from this part apex of ventral plate strongly and triangularly narrowed, with sharp apex, dorsal surface membranous (Figs 9E-G) female tergite 8 subtrapeziodal (Fig. 8C), sternite 8 nearly Y-shaped with short apodeme (Fig. 10A) female tergite 8 trapeziodal, sternite 8 Y-shaped with long apodeme (Fig. 10D) gonocoxite 1.50-1.65× longer than wide, base of gonocoxite 2.50-3.10× longer than wide, base of stylus slanted inward posteriorly, stylus subconical and slanted inward (Fig. 10B) stylus strongly slanted outward posteriorly, stylus conical and slanted outward ...
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... from base to the upper corner of median orifice, from this part apex of ventral plate strongly and triangularly narrowed, with sharp apex, dorsal surface membranous (Figs 9E-G) female tergite 8 subtrapeziodal (Fig. 8C), sternite 8 nearly Y-shaped with short apodeme (Fig. 10A) female tergite 8 trapeziodal, sternite 8 Y-shaped with long apodeme (Fig. 10D) gonocoxite 1.50-1.65× longer than wide, base of gonocoxite 2.50-3.10× longer than wide, base of stylus slanted inward posteriorly, stylus subconical and slanted inward (Fig. 10B) stylus strongly slanted outward posteriorly, stylus conical and slanted outward (Fig. 10E) ramus of spermatheca slightly wider than nodulus (Fig. 10C) ramus ...
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... female tergite 8 subtrapeziodal (Fig. 8C), sternite 8 nearly Y-shaped with short apodeme (Fig. 10A) female tergite 8 trapeziodal, sternite 8 Y-shaped with long apodeme (Fig. 10D) gonocoxite 1.50-1.65× longer than wide, base of gonocoxite 2.50-3.10× longer than wide, base of stylus slanted inward posteriorly, stylus subconical and slanted inward (Fig. 10B) stylus strongly slanted outward posteriorly, stylus conical and slanted outward (Fig. 10E) ramus of spermatheca slightly wider than nodulus (Fig. 10C) ramus of spermatheca distinctly wider than nodulus ( ...
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... (Fig. 10A) female tergite 8 trapeziodal, sternite 8 Y-shaped with long apodeme (Fig. 10D) gonocoxite 1.50-1.65× longer than wide, base of gonocoxite 2.50-3.10× longer than wide, base of stylus slanted inward posteriorly, stylus subconical and slanted inward (Fig. 10B) stylus strongly slanted outward posteriorly, stylus conical and slanted outward (Fig. 10E) ramus of spermatheca slightly wider than nodulus (Fig. 10C) ramus of spermatheca distinctly wider than nodulus ( ...
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... with long apodeme (Fig. 10D) gonocoxite 1.50-1.65× longer than wide, base of gonocoxite 2.50-3.10× longer than wide, base of stylus slanted inward posteriorly, stylus subconical and slanted inward (Fig. 10B) stylus strongly slanted outward posteriorly, stylus conical and slanted outward (Fig. 10E) ramus of spermatheca slightly wider than nodulus (Fig. 10C) ramus of spermatheca distinctly wider than nodulus ( ...
Citations
... In fact, Harris (2011) suggested that after the introduction of the two Larinus species "the populations coalesced with a blended morphology, so the priority name L. obtusus should be used". Recent taxonomic studies suggest that the most promising features by which the two species could be discriminated are subtle differences in the genitalia and (dissected) terminal segments (Gültekin and Anderson, 2017). Thus, it has not been possible to say whether both species were successful or necessary for biological control, nor whether there has been post-release evolution. ...
... Taxonomic identification of a sub-sample of 32 Larinus specimens from four sites in BC and Hanu Conachi, Romania based on morphological characteristics was carried out by one of the authors, Levent Gültekin (Gültekin and Anderson, 2017;Gültekin and Perrin, 2006). Most of these were subsequently compared with mitochondrial sequence CO1 lineage and/or microsatellite genotypes. ...
... Thirty-two individuals were scored to species based on morphological characteristics (Gültekin and Anderson, 2017;Gültekin and Perrin, 2006). All the individuals from White Lake (1) and Spences Bridge (4) were identified as L. minutus. ...
Introductions of biological control agents are unique field experiments to examine the response of novel organisms to new environments. Post-release monitoring is particularly challenging where closely related and morphologically similar biological control agents have been released. Two closely-related phytophagous weevils, Larinus minutus and L. obtusus, were introduced as biological control agents for two major rangeland weeds, diffuse knapweed, Centaurea diffusa and spotted knapweed, C. stoebe subsp. micranthos in North America. The release of the Larinus species coincided with a decline in C. diffusa abundance in many areas. However, it was not clear whether both species of Larinus had become established as they are morphologically very similar. We asked: (1) Could genetic markers be used to identify both the weevil species? (2) Do both weevil species attack both knapweed species in Canada? (3) Are the levels of genetic diversity of the introduced populations of the weevils similar to those of a European source population? (4) Is genetic mixing between the weevil species occurring? Both microsatellite and CO1 mtDNA markers distinguish between the two weevil species. Larinus obtusus was only found on spotted knapweed, while L. minutus was more widely distributed and attacked both weed species. The relatively large initial introductions of weevils to British Columbia (4,300 L. minutus and 5,500 L. obtusus) together with rapid population growth and frequent redistribution among sites has been sufficient to maintain levels of genetic diversity. Results from small samples showed that haplotype, nucleotide diversity and allelic richness of the introduced populations were comparable to those of a European population. We found no evidence for hybridization in the introduced populations.
... It has the smallest body size in the subgenus Phyllonomeus as well as in the genus Larinus. Another species of small body size is Larinus minutus Gyllenhal, 1835 in the subgenus Larinomesius Reitter, 1924 but it is easy to distinguish the species based on differences in the rostrum shape, which is subrectangular in L. minutus, this species also characterised by the epifrons bearing three carinae, underside of head with bi-or trifurcate scales, claws unequal in length, spiculum ventrale Yshaped with long apodeme, gonocoxite elongate, stylus slanted outwardly and other characters (see Gültekin and Anderson, 2017 for full description of this species). However, the new species is similar to both L. minutus and L. obtusus Gyllenhal, 1835 in having the procoxae separate. ...
Two new Larinus Dejean (Curculionidae: Lixinae) species are described, based on specimens in the collection of the Natural History Museum, London. Larinus mumbaicus sp. nov. and Larinus nilgiricus sp. nov. from India, are assigned to the subgenus Phyllonomeus Gistel, 1856. Figures for each species are presented, illustrating morphological characters and differential diagnosis characters. Lectotypes are designated for Larinus saussureae Marshall, 1924 and Larinus assamensis Marshall, 1924. A key to the Indian Larinus is presented. Key words: Larinus, Lixini, Curculionidae, taxonomy, new species, Oriental region
The weevil Larinus sibiricus Gyllenhal and a rich complex of associated hymenopteran parasitoids were reared from flower heads of Xeranthemum annuum L. (Asteraceae) in Bulgaria. As a result, the following taxa were established: Bracon urinator (Fabricius) (Braconidae), Exeristes roborator (Fabricius) (Ichneu-monidae), Cyrtoptyx sp., Norbanus cerasiops (Masi), Pteromalus vibulenus (Walker), Stenoselma nigrum Delucchi (Pteromalidae), Exopristus trigonomerus (Masi) (Torymidae), Leptomastix ephyra Noyes & Hayat (Encyrtidae), Aprostocetus venustus (Gahan), Baryscapus sp. near carthami Graham (Eulophidae), Eupelmus microzonus Förster (Eupelmidae) and Eurytoma curculionum Mayr (Eurytomidae). Three of them (E. curculionum, L. ephyra and N. cerasiops) are recorded for the first time from Bulgaria and L. ephyra is a newly recorded species for the Balkan Peninsula and Europe. New associations with L. sibiri-cus and X. annuum were established for all reared parasitoids except B. urinator.
