Trogus is a genus of
parasitoid wasp found in the
Holarctic and
Neotropic regions. It is placed in the subfamily
Ichneumoninae and the tribe
Ichneumonini.[4]Trogus species are parasites of larvae and pupae of the swallowtail butterfly family,
Papilionidae.[2] The genus consists of twelve extant and one extinct species.
Etymology
The
generic nameTrogus comes from the ancient Greek word τρώγω (trṓgō) meaning "to gnaw" or "to nibble".[5][6][7]
Taxonomy and phylogeny
German entomologist
Georg Wolfgang Franz Panzer created the genus Trogus in 1806. He included one species in his circumscription: Trogus coeruleator,[a] first named in 1804 by
Johan Christian Fabricius as Ichneumon coeruleator.[8][1] In 1829,
Johann Ludwig Christian Gravenhorst included eight species in his taxonomy of Trogus.[9] Some subsequent researchers, for instance
Arnold Förster[3] and
William Harris Ashmead,[10] have referred to a Trogus whose authority is Gravenhorst, but Panzer's sole species in his circumscription of Trogus is included in Gravenhorst's treatment of Trogus and the two of them had the same concept for the genus.[11] In 1840,
John O. Westwood designated Gravenhorst's Trogus alboguttatus to be the type species of Trogus.[12][13] However, this species was later transferred to the genus Goedartia and made its type species.[13] Fabricius's Ichneumon lutorius, included in Gravenhorst's 1829 taxonomy, was also historically considered to be the type species of Trogus; this species is now known as Callajoppa cirrogaster.[2] In 1914, Viereck designated Fabricius's I. coeruleator—the only species Panzer initially included—as the type species for Trogus; this has subsequently been accepted by following taxonomists.[13][14][2]
In 1869, Förster created the genus Dinotomus,[3] but did not designate a type species[2] or include any species.[13] In 1900, Ashmead designated Fabricius's Ichneumon lapidator to be the type species;[10] this was one of three species included in V. Berthoumieu's 1896 taxonomy of Dinotomus.[5][15][2] In 1910,
Per Abraham Roman found Fabricius's I. coeruleator and I. lapidator to be cospecific.[16][2] This led to
Henry Lorenz Viereck synonymizing Dinotomus and Trogus in 1914.[13][2] The generic name Dinotomus comes from the ancient Greek words δεινός (deinós; "strange") and τομή (tomḗ; "segment").[5] The genus Psilomastax, named in 1868 by
Peter Friedrich Ludwig Tischbein, was once considered to be cogeneric with Dinotomus[17][16] hence later with Trogus, until it was reinstated as its own genus in 1961 by Henry Townes and colleagues.[18][2] Ashmead also considered the genus Tricyphus, named by
Joseph Kriechbaumer in 1898, to be a synonym of Trogus,[10][19] but it has since been accepted as its own genus.[20]
Förster placed Trogus in a new family Trogoidae in 1869 alongside Dinotomus and Automalus.[3][19][20] In 1895, Ashmead created the tribe Trogini within Ichneumoninae.[21][20] In 1962,
Gerd Heinrich placed Trogus in a new subtribe within Trogini, namely Trogina.[14] In 1979, Robert W. Carlson illegally
emended the subtribe name to Trogusina.[15][11] In 2002, Sime and Wahl synonymized Trogini with Heresiarchini because they found Heresiarchini to be
paraphyletic with respect to Trogini; they renamed the clade historically known as Trogini as the Callajoppa genus-group and the clade historically known as Trogina as the Trogus subgroup.[20] In 2021, Santos and colleagues synonymized the tribe Heresiarchini under Ichneumonini and demonstrated that the Trogus subgroup did not nest within the Callajoppa group. Further, the Trogus subgroup of earlier authors did not represent a
monophyletic lineage.[4]
Description and identification
Trogus species have a body length of 14–18 mm (0.55–0.71 in). Their abdomens resemble a row of rectangular blocks due to each abdominal segment having thick edges and deep cuts.[22] An
autapomorphy of Trogus is a concave
apical edge of the
clypeus.[20]
Distribution
Trogus species are found in the
Holarctic and
Neotropics.[2]: 584 Sime and Wahl, in part following
Gerd Heinrich, proposed Trogus originated in the
Palaearctic and crossed into North America following ancestors of the Papilio machaon clade over
Beringia.[2]: 588–589 Most Trogus species are found in North America.[2]: 588
Trogus select the pupae and larvae of
swallowtail butterflies as hosts. The hosts are specifically limited to the tribes
Graphiini and
Papilionini within the subfamily
Papilioninae. However, many species within these tribes are not parasitized by Trogus species; systematic gaps are thought to be a result of plant chemistry in the preferred food for various swallowtail larvae.[2] The butterfly genera with the most reliable host records for Trogus are Papilio and Eurytides. Trogus species vary in how specialized they are, ranging from having one to ten possible swallowtail hosts.[20] The host caterpillars are commonly collected by lepidopterists, amateur and professional, leading to confidence in host range delineation.[2]
All Trogus species are thought to have a similar biology.[26] One egg is laid per larva;[22] some species like T. pennator or T. lapidator can lay their eggs in caterpillars as early as the first
instar.[20][27]Trogus species make their emergence hole by secreting a fluid which softens the pupa cuticle.[26][27] They emerge as adults through the wing pad creating a distinctive lateral hole; this emergence location is
apomorphic for the Trogus subgroup.[20]Diapause, extended diapause, and lack of diapause have all been observed.[27]
Species
David B. Wahl and Karen R. Sime's 2006 revision of the genus recognized the following twelve extant species:[2]
^
abcdFoerster, [Arnold] (1869). "Synopsis der Familien und Gattungen der Ichneumonen". Verhandlungen des Naturhistorischen Vereins der Preussischen Rheinlande und Westfalens. 25: 188.
hdl:2027/coo.31924018319255.
^
ab
Santos, Bernardo F.; Wahl, David B.; Rousse, Pascal; Bennett, Andrew M. R.; Kula, Robert; Brady, Seán G. (2021). "Phylogenomics of Ichneumoninae (Hymenoptera, Ichneumonidae) reveals pervasive morphological convergence and the shortcomings of previous classifications". Systematic Entomology. 46 (3). Royal Entomological Society: 704–724.
doi:
10.1111/syen.12484.
S2CID235363032.
^
abFabricius, Ioh. Christ. (1804). "Ichneumon".
Systema Piezatorum. Brunsvigia: Carolus Reichard. p. 68.
^Gravenhorst, I. L. C. (1829).
"Genus III. Trogus". Continens Tryphones, Trogos, Alomyas et Cryptos. Ichneumonologia Europaea. Vol. 2. Vratislavia: Sumtibus Auctoris. pp. 369–393.
^Westwood, J. O. (1840).
"Synopsis of the Genera of British Insects". An Introduction to the Modern Classification of Insects. Vol. 2. London: Longman, Orme, Brown, Green, and Longmans. p. 58.
^
abHeinrich, Gerd H. (1962). "Synopsis of Nearctic Ichneumoninae Stenopneusticae with Particular Reference to the Northeastern Region (Hymenoptera): Part VII Synopsis of the Trogini Addenda and Corrigenda". Memoirs of the Entomological Society of Canada. 94 (S29): 807–886.
doi:
10.4039/entm9429fv.
^
abCarlson, Robert W. (1979).
"Family Ichneumonidae". In Krombein, Karl V.; Hurd, Paul D. Jr.; Smith, David R.; Burks, B. D. (eds.). Symphyta and Apocrita (Parasitica). Catalog of Hymenoptera in America North of Mexico. Vol. 1. Washington, DC: Smithsonian Institution. pp. 538–539.
^Townes, Henry; Townes, Marjorie; Gupta, Virendra K. (1961). A Catalogue and Reclassification of the Indo-Australian Ichneumonidae. Memoirs, American Entomological Institute. Vol. 1. Ann Arbor, MI: American Entomological Institute. pp. 387–399.
^
abHopper, H. Pearson (1939). "A Synoptical Revision of the Tribe Trogini Ashmead of the United States and Canada (Hymenoptera: Ichneumonidae)". Transactions of the American Entomological Society. 65 (4): 307–346.
JSTOR25077444.
Sime, Karen R. (2002). "Experimental Studies of the Host-Finding Behavior of Trogus pennator, a Parasitoid of Swallowtail Butterflies". Journal of Chemical Ecology. 28 (7): 1377–1392.
doi:
10.1023/A:1016296418857.
PMID12199502.
S2CID20183366.