Onichodon canadensis (Brown, 1940)

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 canadensis (Brown, 1940) fifth instar ( Figs. 1–5 )

Diagnosis. The shape of the dorsal prothoracic scleromes, along with a short, narrowly bifurcate first lateral projection of the head capsule, weakly sclerotized caudal end of the ninth abdominal segment, and oblong circular ring of asperities around the anal region should distinguish this species from its close relatives, O. orchesides and O. rugicollis .

Specimens Examined. Eight mature larvae collected at USA: Wisconsin: Marquette County, T17 N R10 E sec 8, 5 May 1997, Daniel K. Young, in paper birch (1 larva) ; Oconto County, T29 N R17 E sec 19, 10 May 1997, Robert L. Otto, in paper birch (3 larvae) ; along Bear Paw Road , 45°11.716′N, 88°24.842′W, 16 April 2010, Robert L. Otto, in paper birch stump (4 larvae) .

Description. Length 27.0–35.0 mm, width 3.0–4.0 mm. Orthosomatic. Body ( Fig. 1 ): Subcylindrical, sides parallel, yellow with head and prothoracic sclerome patches 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. 2 ): Strongly flattened, prognathous, and inserted into prothorax. Dorsal cephalic disc oblong, subtrapezoidal; median ridge shallow, distinct. Ventral cephalic disc similar to dorsal side, except surface unmodified, simple. Anterior portion of the head capsule heavily sclerotized. Posterior areas of the head capsule unsclerotized. Each lateral side of head capsule with 6 projections. First lateral projections short, narrowly bifurcate, directed anterolaterally. Second through 6 th lateral projections directed anterolaterally. Antennae minute, arising between 5 th and 6 th lateral projections. Scape not visible. Pedicel elongate. Sensorum and flagellum subequal in length. Sensory papillae indistinct. Mandibles minute, resting in the mesal acumination of the head capsule between the 6 th lateral projections. Each mandible heavily sclerotized, distinct, oval, longer than wide with 2 outwardly projecting teeth. Maxillary palpi extremely small,

4) Head and thoracic region, ventral view; 5) Abdominal segments VIII-IX, ventral view.

3-segmented. Ligula, mala, lacinia, and galea not visible. Hypostomal rods absent. Prothorax ( Figs. 3, 4 ): Subequal to subsequent 2 thoracic segments. Tergum with pair of subtriangular scleromes, caudally rounded with a small projection. Trapezoidal microtrichial patch between scleromes. Tergum and sternum without areoles. Sternum with triangular scleromes and more rounded microtrichial patch. Meso- and metathorax: Each tergum with kidney-shaped microtrichial patch consisting of narrow triangular extension coming from mediocaudal region directed towards posterior end. Sterna similar to terga, except microtrichial patches more oblong, oval. Anterior 3/4 of each tergum with longitudinal plicae and carinae surrounding each microtrichial patch and extending towards posterior end. Mesothorax without spiracles. Metathorax with pair of small, oval areoles near posterior end. Triangular extension near mediocaudal area of microtrichial patch shorter. Metathoracic sternum with oblong areole near posterior end. 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 triangular on segment VIII. Terga and sterna I-VIII with oblong, oval areole near posterior end. Tergum IX without microtrichial patch and scleromes, sparsely punctate near caudal end; sternum ( Fig. 5 ) with prominent, oblong ring of asperities around anal region. Urogomphi absent on segment IX. Spiracles annular-biforous.

Distribution. Onichodon canadensis is known from CANADA: New Brunswick, Nova Scotia, Ontario, Prince Edward Island, and Québec; USA: Maine, Massachusetts, Michigan, Minnesota, New Hampshire, New York, Pennsylvania, and Wisconsin ( Muona 2000; Majka 2007). All specimens used in this study came from Wisconsin.

Biology. Onichodon canadensis is an infrequently collected species found largely in the northeastern United States and eastern Canada with limited distribution. The species thrives in a variety of forest systems. In Wisconsin, I collected adults and larvae in bedrock glade, northern dry-mesic forest, northern hardwood swamp, northern mesic forest, northern wet-mesic forest, oak barrens, and southern mesic forest. I found one adult cadaver inside its pupal chamber within a rotten paper birch ( Betula papyrifera Marshall ; Betulaceae ) log. Two adults were also taken in a hole excavated by a woodpecker near Fanny Lake in northern Oconto County. Based on specimen labels, collectors in Wisconsin have found the species in a flight intercept trap, at light traps, at blacklight traps, on a glueboard, in purple prism traps (Synergy Semiochemicals, British Columbia), and on a girdled ash tree. Muona (2000) wrote that O. canadensis was reared from yellow birch ( Betula alleghaniensis Britton ) in New Hampshire, reared from beech ( Fagus grandifolia Ehrhart ; Fagaceae ) in Québec, collected at blacklight in New Hampshire, and taken on red spruce ( Picea rubens Sargent ; Pinaceae ) in Maine.

Majka (2007) recorded the species in red spruce, deciduous and mixed hemlock, balsam fir ( Abies balsamea (L.) Miller; Pinaceae ), and black spruce ( Picea mariana (Miller) Britton, Sterns, and Poggenburg ) forest systems in several Canadian Maritime provinces. Webster et al. (2012) obtained 40 adults in various forest systems in New Brunswick during the months of July and August. Thirty-seven specimens were collected from Lindgren funnel traps, while one was obtained with window traps and two others from black light traps. These 40 beetles were taken in mature hardwood forests with beech, an old red oak ( Quercus rubra L.) forest, an old silver maple ( Acer saccharinum L.; Aceraceae ) swamp, an old mixed forest with red spruce, white spruce ( Picea glauca (Moench) Voss ), white pine ( Pinus strobus L.; Pinaceae ), red pine ( Pinus resinosa Aiton ), balsam fir, eastern white cedar ( Thuja occindentalis L.; Cupressaceae ), red maple ( Acer rubrum L.) and Populus sp. (Salicaceae) , a red spruce forest with red maple and balsam fir, and an old-growth eastern white cedar forest system.

During my collections, all O. canadensis larvae were extracted exclusively from rotten paper birch in Wisconsin on separate occasions in 1997 and 2010. All extracted larvae were found in moist, firm, hard sections of the log or stump. Larvae were positioned parallel with the grain of the sapwood and burrowing between layers of wood fibers, leaving no galleries behind them. Their unique head capsule is useful as a wedge, allowing the larva to move through the sapwood. Mature larvae were observed constructing pupal chambers at about 2.5 cm beneath the bark layer. Larvae assumed a U-shaped position as they molted to the pupa in the chamber. Only four adults emerged from the wood pieces in 1997 and 2010. None of their behavior was recorded nor were there attempts to breed these specimens to obtain further information on the species’ life history.

Figures

Fig. 1. Onichodon canadensis, fifth instar, dorsal habitus.

Figs. 2–5. Onichodon canadensis, fifth instar. 2) Head, dorsal view; 3) Head and thoracic region, dorsal view;