Onichodon rugicollis (Fall, 1928)

Otto, Robert L., 2013, Eucnemid Larvae of the Nearctic Region. Part III: Mature Larval Descriptions for Three Species ofOnichodonNewman, 1838 (Coleoptera: Eucnemidae: Macraulacinae: Macraulacini), with Notes on Their Biology, The Coleopterists Bulletin 67 (2), pp. 97-106 : 97-106

Onichodon rugicollis (Fall, 1928) fifth instar ( Figs. 11–15 )

Diagnosis. The shape of the dorsal prothoracic scleromes, along with a widely bifurcate first lateral projection of the head capsule, and sclerotized caudal end of the ninth abdominal segment should distinguish this species from its close relatives, O. canadensis and O. orchesides .

Specimens Examined. Five mature larvae and three larval exuviae collected at USA: Kentucky: Woodford County, 40 km NW Lexington, Clyde E. Buckley Wildlife Sanctuary, 24–25 March, 1995, Robert L. Otto, reared on 27 April, 1995, in rotten wood (3 exuviae) ; Michigan: Ingham County, M.S.U. – Sanford Woodlot, May 3, 1960, C.F. Gibbons, in rotten wood (3 larvae) ; Wisconsin: Sauk County, Pine Hollow, 43°22′26″N / 89°54′20″W, 7 May, 2007, Kelly M. Zivicki, in dead log (2 larvae) .

Description. Length 30.0–34.0 mm, width 3.0–4.0 mm. Orthosomatic. Body ( Fig. 11 ): Subcylindrical, sides parallel, yellow with head, prothoracic sclerome patches, and caudal end of 9 th abdominal segment dark brown. Setae reduced or absent. Pair of small legs reduced to dome-like structures present near posterolateral areas of each thoracic segment. Dorsal and ventral microtrichial patches slightly darker than their surrounding areas. Head ( Fig. 12 ): Strongly flattened, prognathous, and inserted into prothorax. Dorsal and ventral cephalic discs oblonged, subtrapezoidal and simple. Anterior portion of the head capsule heavily sclerotized. Posterior areas of head capsule unsclerotized. Each lateral side of head capsule with 6 projections. First lateral projections slightly elongate, very widely bifurcate, directed anteriorally. Second through 6 th lateral projections directed anterolaterally. Second lateral projection short and narrowly separated from 3 rd. Antennae minute, arising between 5 th and 6 th lateral projections. Scape not

14) Head and thoracic region, ventral view; 15) Abdominal segments VII-IX, ventral view.

visible. Pedicel elongate. Sensorum and flagellum subequal in length. Sensory papillae indistinct. Mandibles minute, resting in the mesal acumination of the head capsule between 6 th lateral projections. Each mandible heavily sclerotized, distinct, oval, longer than wide with 2 outwardly projecting teeth. Maxillary palpi extremely small, 3-segmented. Ligula, mala, lacinia, and galea not visible. Hypostomal rods absent. Prothorax ( Figs. 13, 14 ): Subequal to subsequent 2 thoracic segments. Tergum with pair of square scleromes, caudally scalloped, irregularly shaped. Subtriangular microtrichial patch between scleromes. Tergum and sternum without areoles. Sternum with triangular scleromes and more rounded, slightly oblonged and smaller microthrichial patch. Meso- and metathorax: Each terga and sterna with kidney-shaped microtrichial patch of short triangular extension coming from mediocaudal region directed towards the posterior end. Surfaces of terga and sterna with longitudinal plicae and carinae just caudad of each microtrichial patch and extending towards posterior end. Each terga with pair of elongate oval-shaped areoles near posterior end. Oblong areole present near posterior end of metathoracic sterna. Mesothorax without spiracles. Abdomen: Segments I-IX subequal in length and width. Terga and sterna I-VIII with microtrichial patches that successively change from oval on segment I to subtriangular on segment VIII. Terga and sterna I-VIII with oval areole near posterior end, each successively narrower. Tergum IX without microtrichial patch, sparsely punctate near the caudal end; sternum ( Fig. 15 ) heavily sclerotized at caudal half with prominent, circular ring of asperities around anal region. Urogomphi absent on segment IX. Spiracles annular-biforous.

Distribution. Onichodon rugicollis is known from USA: Alabama, Florida, Illinois, Kentucky, Louisiana, Mississippi, North Carolina, Pennsylvania, Texas, and Wisconsin ( Muona 2000; Otto 2010). It is recorded here as a new state record for Michigan. All specimens used in this study came from Kentucky, Michigan, and Wisconsin.

Biology. Onichodon rugicollis is an uncommon and widespread species, largely distributed in the southern United States. In Wisconsin, O. rugicollis was found in a variety of forest systems. Adults and larvae were taken in northern hardwood swamp, northern mesic forest, oak barrens, oak opening, southern dry forest, and southern mesic forest. Two adults were reared from damp oak wood collected in oak opening woodland in southwestern Wisconsin. One adult was observed emerging from a dead, standing tree trunk. Based on label information, many adults were taken in a flight intercept trap, Lindgren funnel traps, and purple prism traps deployed throughout the southeastern two-thirds of Wisconsin. Muona (2000) wrote that the species was taken at blacklight traps. Otto (2010) wrote that several adults were reared from larvae in a rotten log in Kentucky and adults were taken on dead trees and fungus in northwestern Pennsylvania.

Figures

Fig. 11. Onichodon rugicollis, fifth instar, dorsal habitus.

Figs. 12–15. Onichodon rugicollis, fifth instar. 12) Head, dorsal view; 13) Head and thoracic region, dorsal view;