Scolopostethus affinis, a species native to the Palearctic region, is reported from two localities in Montreal, Quebec. The species appears established and breeding in Quebec and is a new alien species in North America. A description of S. affinis is given, with illustrations, and details of the life cycle and diagnostic characters.

Canada, Hemiptera, Rhyparochromidae, Scolopostethus affinis

The genus Scolopostethus Fieber (Rhyparochromidae: Rhyparochrominae: Drymini) comprises a group of 34 relatively small species that occur within the Holarctic and northern Ethiopian biogeographic regions (Slater 1964, Dellapé and Henry 2019). One species, S. thomsoni Reuter, is Holarctic occurring across Northern North America, four are Nearctic (Henry and Froeschner 1988) and 29 are Palearctic.

Scolopostethus affinis (Schilling) is an Old-World species, a Euro-Siberian element in the fauna, known from all of Europe, including Russia, with recorded occurrence in Asia (Péricart 1998). In the British Isles, it is quite common, and occurs on a wide variety of soils where it is often associated with nettles (Urtica dioica L.) (Southwood and Leston 1959). It is usually brachypterous, but macropters are sometimes present (Southwood and Leston 1959).

There is an extensive literature on S. affinis, as documented by Slater (1964) and Dellapé and Henry (2019). Slater (1964) lists the references that give illustrations. In the recent literature, a colour illustration is included in Southwood and Leston (1959), and Péricart (1998) provides illustrations relevant for accurate identification. The latter two authors provide keys to European species. Larson and Scudder (2018) describe and illustrate the two species then recognised on the prairies and in eastern Canada and discuss previously reported species.

Eyles (1963a) described the life cycle of S. affinis in England and concluded that it has a single generation a year, but Southwood and Leston (1959) state that it is either single-brooded, with a long oviposition season, or double-brooded. Eyles (1963b) describes the egg and the five immature stages, although these immature stages cannot be separated from those of S. thomsoni and have a similarly timed life cycle. However, Eyles and Blackith (1965) found that S. affinis did not successfully hybridise with other species of Scolopostethus.

Eyles (1964) showed that seeds are the principal item of food in the diet of S. affinis. When larvae were reared on different seeds, seeds of the stinging nettle (Urtica dioica L.) produced the most productive growth curve. Eyles (1963a) found that S. affinis in England overwinters in nettle litter or in leaf litter near nettles, and was most readily collected in nettles. Eyles (1964) showed that although S. affinis survived to the third instar on a diet of beetle larvae, it scarcely showed any growth.

Quebec specimens have been compared with material collected in England and Germany. Measurements were obtained from this European material, but total length of Quebec specimens is also given.

Quebec specimens are deposited in the following collections:

CNC Canadian National Collection, Agriculture and Agri-Food Canada, Ottawa;

DJL D.J. Larson collection;

GGES G.G.E. Scudder collection.

All European specimens studied are in the latter collection.

This species was collected in Outremont, Quebec, in a ruderal area around a newly constructed building, with many weeds, including dandelion (Asteraceae: Taraxacum sp.), knapweed (Asteraceae: Centaurea sp.), nettles (Urticaceae: Urtica dioica L.), burdock (Asteraceae: Arctium sp.), and lamb’s quarters (Amaranthaceae: Chenopodium album L.). Although late-instar nymphs were abundant, proving the species was present as a reproducing colony, no specimens were retained.

The true bug fauna of Quebec is well known. If this apparently synanthropic species had been present in Quebec for any length of time, it is highly probable it would have been discovered before now. Thus, S. affinis is likely a recent introduction into the fauna. As the species has a wide range in the Palearctic, indicating it can survive in diverse environments, and is clearly adapted to some types of human-modified environments, it is likely to persist and spread in North America. The North American population contains both brachypters and macropters so rapid dispersal by flight is a possibility but also synanthropic species have the advantage of human assisted dispersal so that rapid spread is possible. Fortunately, this species is not known to have any deleterious effects on crops and its propensity of feeding on seeds of plants we regard as weeds may make it a welcome addition to our environments. It is not known how it might interact with North American species although it does coexist with a diverse fauna of Palearctic Scolopostethus, which includes the Holarctic S. thomsoni, so it may occupy an uncontested niche.

Launi Lucas kindly prepared the manuscript. We thank Thomas Henry, Laurence Livermore and an anonymous reviewer for their very helpful and constructive reviews.