Nemobius sylvestris (Bosc, 1792)

Woo, Brandon, 2022, Nemobius sylvestris (Orthoptera, Trigonidiidae, Nemobiinae) in North America, Journal of Orthoptera Research 31 (1), pp. 47-53 : 47

Nemobius sylvestris (Bosc, 1792)

Material examined. -

USA • 4♂, 3♀; New York, Monroe Co, Channing H. Philbrick Park ; 43.127598, -77.482463; 24 May 2021; B. Woo leg ;. 1♂, CUIC; 3♂, 3♀, TAMUIC • 1 nymph; same locality; 08 May 2021; https://www.inaturalist.org/observations/78163683 • 1 nymph; same locality; 26 May 2021; https://www.inaturalist.org/observations/80436300 • 1 nymph; same locality; 03 June 2021; https://www.inaturalist.org/observations/82337154 • 1 nymph; same locality; 25 June 2021; https://www.inaturalist.org/observations/84491906 • 1♀; Univ. of Rochester River Campus ; 43.131557, -77.631649; 11 September 2020; https://www.inaturalist.org/observations/65836637 • 1♂; MLK Jr. Memorial Park ; 43.154131, -77.6023841; 16 July 2021; https://www.inaturalist.org/observations/87327902 • 1 nymph; Washington; King Co.; Renton ; 47.4827, -122.225945; 12 May 2021; https://www.inaturalist.org/observations/78524305 • 1 nymph; SeaTac Park ; 47.481667, -122.313611; 07 May 2021; https://www.inaturalist.org/observations/82370524 • 1♀; Renton ; 07 November 2020; https://www.inaturalist.org/observations/64390177 • 1 nymph; 106th Ave NE; 47.701607, -122.198671; 23 October 2020; https://www.inaturalist.org/observations/63410553 • 1 nymph; Renton ; 47.492725, -122.180177; 08 July 2020 https://www.inaturalist.org/observations/52450292 • 1 nymph; Codiga Park ; 47.489145, -122.26908; 26 April 2020; https://www.inaturalist.org/observations/43798862 • 1♀; McAuliffe Park ; 47.704563, -122.197816; 06 October 2019; https://www.inaturalist.org/observations/34487275 • 1♀; Bothell Landing Park ; 47.756939, -122.210152; 07 October 2018; https://www.inaturalist.org/observations/17427199 • 1 nymph; Hitt's Hill Park ; 47.55413, -122.285381; 28 April 2018; https://www.inaturalist.org/observations/11708950 • 1 nymph; same locality and date; https://www.inaturalist.org/observations/11708950 • 1 nymph; Lewis Creek Park; 47.550518, -122.124166; 25 May 2017; https://www.inaturalist.org/observations/29595726 • 1♂; White Center ; 01 November 2014;https://www.inaturalist.org/observations/1082123 • 1♀; Westcrest Park ; 01 November 2014; https://www.inaturalist.org/observations/1054939 • 1 nymph, Pierce Co.; 3rd St. E; 47.257305, -122.180313; 20 June 2020; https://www.inaturalist.org/observations/50369172 .

Characters to separate from native North American crickets. -

The genus Nemobius currently includes six species distributed in the Old World and in the Neotropics, although Barranco et al. (2013) reviewed these six species and concluded that only N. sylvestris (the type species of the genus) and their newly described N. interstitialis Barranco, Gilgado & Ortuño, 2013, are likely to belong in the genus. N. interstitialis can be ruled out since it lacks tympana, possesses differently shaped tegmina, and occurs in a restricted, partially subterranean, rocky habitat ( Barranco et al. 2013). Historically, the entire Nemobiine fauna of the USA was included in Nemobius ( Hebard 1913) before being split into five different genera by Vickery and Johnstone (1970): Allonemobius , Eunemobius , Neonemobius , Pictonemobius , and Hygronemobius . Nemobius sylvestris can be separated from all other members of the subfamily present in North America by several morphological characters, most notably the absence of glandular hind tibial spines in the male (present in males of all North American genera) and female ovipositor shape and tooth dentation (Fig. 1 ). The ovipositor is straight,about as long as the hind femur, and without teeth. Straight ovipositors are also found in Allonemobius and Pictonemobius , but these genera possess large teeth on the upper valves ( Vickery and Johnstone 1970). The distoventral spurs of the hind tibiae of Nemobius are unequal in length, with the inner spur slightly shorter than the outer. In the North American genera, these spurs are either equal in length or the inner spur is much longer than the outer. In the field, both adults and nymphs of N. sylvestris may be recognized by their unique color pattern, which is unlike any other North American nemobiine: head black with pale Y-shaped marking, and pronotum very pale with dark speckles (Figs 2 , 3 ).

In Washington (WA), the only other nemobiine species present is Allonemobius fasciatus (De Geer, 1773), which has the distoventral spurs more robust, with the inner spur longer than the outer. It also has a toothed ovipositor as described above, as well as longitudinal stripes on the head that are absent in Nemobius . A. Allonemobius fasciatus occurs in open grassy meadows as opposed to the woodland leaf litter habitat of N. sylvestris .

In New York (NY), there are five species of Allonemobius , two of Neonemobius , and one of Eunemobius . These are all readily distinguishable from Nemobius by the hind tibial spur armature, ovipositor shape, and color patterns. All of these species are also univoltine, with only eggs overwintering. Habitat is another useful clue-of the eight native NY species, only three habitually inhabit woodland leaf litter.

Habitat and phenology in New York State. -

At Channing H. Philbrick Park, nymphs (Fig. 2 ) were collected in leaf litter of a small patch of forest surrounded by suburbs. Although the major forest trees were native species, such as Platanus occidentalis L., most of the lower vegetation in the area consisted of introduced invasive European plants, including Chelidonium majus L., Vincetoxicum rossicum (Kleopow) Barbar., Artemisia vulgaris Burm.f., Alliaria petiolata (M.Bieb.) Cavara & Grande, Vinca minor L., and Hedera helix L.. Nymphs of Nemobius sylvestris were easy to collect as they were far less active than native NY ground crickets (pers. obs.). Individuals cohabitated well and were never seen to cannibalize. In captivity under similar temperature conditions to outdoors, the first male matured on June 20th and the first female on June 28th.

Figures

Figure 1. Morphological characters of Nemobius sylvestris compared to Allonemobius socius. A. N. sylvestris male right hind tibia, dorsal view; B. A. socius male right hind tibia, dorsal view. Arrow points to glandular tibial spine; C. N. sylvestris ovipositor. Inset shows detail; D. A. socius ovipositor. Inset shows detail.

Figure 2. Nemobius sylvestris female (A) and male (B) nymphs from Channing H. Philbrick Park.

Figure 3. Nemobius sylvestris female (A) and male (B) adults from Channing H. Philbrick Park.