ISSN 1911-2173

A beginner-friendly key to the spider families (Arachnida: Araneae) known from the Canadian Prairie Provinces (Alberta, Saskatchewan, and Manitoba)

Kirra Kent1,2*

Jaime Pinzon2

Heather Proctor1

1Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9

2Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre, Edmonton, Alberta, Canada T6H 3S5

* Corresponding author: Kirra Kent, email: [email protected]

[Date]: A [addendum/corrigendum] has been published for this paper — doi:10.3752/cjai.[YYYY.##]

A beginner-friendly key to the spider families (Arachnida: Araneae) known from the Canadian Prairie Provinces (Alberta, Saskatchewan, and Manitoba)

A beginner-friendly key to the spider families (Arachnida: Araneae) known from the Canadian Prairie Provinces (Alberta, Saskatchewan, and Manitoba)

Kirra Kent1,2*

Jaime Pinzon2

Heather Proctor1

1Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9

2Natural Resources Canada, Canadian Forest Service, Northern Forestry Centre, Edmonton, Alberta, Canada T6H 3S5

* Corresponding author: Kirra Kent, email: [email protected]

[Date]: A [addendum/corrigendum] has been published for this paper — doi:10.3752/cjai.[YYYY.##]

Abstract

The Canadian Prairie Provinces (Alberta, Saskatchewan and Manitoba) are home to species from 29 of the 45 spider families currently found in Canada. Here we provide a beginner-friendly dichotomous key to the spider families of the Canadian Prairies. The key includes numerous photos, line drawings, and simplified definitions of anatomical characters necessary for family-level identification. For each family we include an illustrated summary of important character states, a whole-body photo of an exemplar of the family, and number of species of the family currently reported from the Prairie Provinces

Habronattus sp. by Heather Proctor

Habronattus sp. by Heather Proctor

Introduction

Dichotomous taxonomic keys are used to aid identification of specimens to predefined levels of taxonomic specificity and predate the Linnaean naming system by 60 years (Griffing 2011). However, despite over 300 years of use, keys still have design and implementation issues. For example, they are often challenging for individuals unfamiliar with taxon-specific technical jargon (Walter and Winterton 2007) or morphological characters. Conversely, keys are not always useful to specialists on the focal group. Experts often proceed through keys in a non-linear fashion or can identify species by sight without using a key at all. This can result in experts not recognizing when keys include errors. Keys often also use ambiguous wording or refer to relative and dependent character states. For example, “very feebly sinuate” in the Lindroth (1961-1969) key to Carabidae (Coleoptera; pg. 65) is dependent on an a priori understanding of the “strongly sinuate” state of this trait.

For spider identification in North America, keys to families and genera are available for taxa found north of Mexico (Ubick et al. 2017). For Canada, Dondale & Redner (1978) produced a national key to families, and national keys to genera and species for several families are also available (Dondale & Redner, 1978, 1982, 1990, Platnick & Dondale, 1992, Dondale et al., 2003). Although such geographically broad keys are more comprehensive than regional keys, they normally contain more couplets, and the complexity of such keys can be daunting to new users. In Canada, regional (provincial or territorial) spider identification keys are lacking with the exception of Guide d’identification des araignées (Araneae) du Québec (Paquin & Dupérré 2003), which provides a comprehensive guide for Quebec. Provided that the user is aware of changes to family-level taxonomy that have occurred since 2003 (e.g., splitting of the Corinnidae into three families), this key is currently also useful for most other provinces in Eastern Canada. Paquin & Dupérré (2003) includes a family-level key, genus-level keys for some families, and detailed illustrations that allow users to make species-level determinations of spiders in Quebec.

Currently, no family-level key specific to the spiders of the Prairie Provinces of Canada (Alberta, Saskatchewan and Manitoba) is available. As stated above, the use of regionally-specific keys can increase efficiency and reduce error. The key in Paquin & Dupérré (2003) includes five more families than the 29 currently recorded across the Prairie Provinces (Cárcamo et al. 2014): Atypidae, Dysderidae, Nesticidae, Oecobiidae and Theridiosomatidae. Although this is not a large number relative to the number of spider families globally (131 families: World Spider Catalog 2022) or reported for Canada (45 families: Canadian Endangered Species Conservation Council 2016; Bennett et al. 2019), having to navigate and interpret additional couplets leads to more processing time per spider and an increased potential for identification errors.

Most published spider keys for Canadian fauna use text and line illustrations (e.g., Dondale and Redner 1990; Paquin & Dupérré 2003). Although line illustrations can effectively convey the size, shape and position of structures, they may leave out potentially useful details and are subject to the illustrator’s biases and interpretations. We aimed to produce a key that uses photographic images as well as line illustrations to provide as much relevant visual information as possible to aid in family-level identification of spiders of the Prairie Provinces without being overwhelming. Also, keys for the identification of spiders and many other taxa include morphological terminology that is often novel to users not already familiar with the taxon. Separate glossaries for such terms are sometimes associated with keys but using them typically requires moving from the couplet to another page to find the definition (which may or may not provide clarity). We aimed to reduce the need to look up terminology by providing clear, often illustrated, descriptions of potentially unfamiliar morphological terms within the couplets.

Because of their ubiquity and diversity, spiders are frequently used in ecological studies as indicators of disturbance or for general estimation of local biodiversity (Bowden and Buddle 2010; Lowe et al. 2018; Pinzon et al. 2016; Wayland and Crosley 2006). Spider families generally align with ecological guild divisions, meaning family-level identification can offer insight into the ecological structure of a site of interest, such as plant composition or ground surface cover (Cardoso et al. 2011), and can provide information of general natural history (Bradley 2012). Although less informative than species-level data, family-level data are more achievable for those who are new to spider identification and desire to include spiders as part of their research data. The intended audience of this key includes amateur naturalists and other “citizen scientists” as well as professional ecologists who require only family-level identification or need to sort samples to family-level prior to using more specialized literature such as Dondale & Redner (1990) to identify to genus or species.

Methods

Taxa Included

We followed the family concepts of the World Spider Catalog (2022). The 29 families included in this key (Table 1) have representatives in one or more of the Prairie Provinces (Alberta, Saskatchewan and Manitoba) in the current checklists for Canada (Canadian Endangered Species Conservation Council 2016; Bennett et al. 2019). Users who are identifying spiders collected in Alberta near the border with British Columbia, or within BC, should be aware that 13 additional families occur in BC that have not yet been recorded from the Prairie Provinces: Antrodiaetidae, Dipluridae, Mecicobothriidae (all from the Mygalomorphae), Anapidae, Dysderidae, Miturgidae, Nesticidae, Oecobiidae, Oonopidae, Pimoidae, Segestriidae, Trachelidae and Zodariidae (Canadian Endangered Species Conservation Council 2016; Bennett et al. 2019). Likewise, users in eastern Manitoba should be aware that there are seven families that occur in Ontario that have not yet been recorded from the Prairie Provinces: Atypidae (Mygalomorphae), Dysderidae, Nesticidae, Oonopidae, Scytodidae, Theridiosomatidae and Trachelidae (Canadian Endangered Species Conservation Council 2016). Conversely, all families reported in Northwest Territories and Nunavut also occur in the Prairie Provinces.

Table 1: Checklist of the 29 spider families reported from the Canadian Prairie Provinces (AB; Alberta, SK: Saskatchewan, MB: Manitoba). Users identifying spiders collected near the border of Alberta and British Columbia or the border of Manitoba and Ontario should be aware that there are 16 additional families found in these two provinces that have not yet been recorded in the Prairie Provinces (see Methods for a list of these families).

Family Province Guild* Classical capture methods
AB SK MB
Agelenidae x x x Sheet web Pitfall
Amaurobiidae x x x Sheet web Pitfall
Anyphaenidae x x x Other hunters Uncommon with classical methods
Araneidae x x x Orb web Beating/Sweeping
Cheiracanthiidae x - - Other hunters Pitfall/Sweeping
Clubionidae x x x Other hunters Beating/Pitfall/Sweeping
Corinnidae x x x Ground hunters Pitfall
Cybaeidae x x x Sheet web Pitfall
Desidae x** - - Ground hunters/Sheet web Uncommon with classical methods
Dictynidae x x x Ground hunters/Sheet web Beating/Pitfall
Gnaphosidae x x x Ground hunters Pitfall
Hahniidae x x x Ground hunters/Sheet web Pitfall
Linyphiidae x x x Other hunters/Sheet web Beating/Pitfall/Sweeping
Liocranidae x x x Ground hunters Pitfall
Lycosidae x x x Ground hunters Pitfall
Mimetidae x - x Specialists Beating/Pitfall/Sweeping
Mysmenidae x - - Space web Uncommon with classical methods
Oxyopidae - x x Other hunters Beating/Sweeping
Philodromidae x x x Other hunters Pitfall
Pholcidae x x x Space web Uncommon with classical methods
Phrurolithidae x x x Ground hunters Pitfall
Pisauridae x x x Sheet web Pitfall
Salticidae x x x Other hunters Beating/Sweeping
Telemidae x x - Sheet web Uncommon with classical methods
Tetragnathidae x x x Orb web Beating/Sweeping
Theridiidae x x x Space web Beating/Pitfall/Sweeping
Thomisidae x x x Ambush hunters Beating/Pitfall/Sweeping
Titanoecidae x x x Space web Pitfall
Uloboridae x x x Orb web Beating/Pitfall/Sweeping

* Guilds following Cardoso et al. (2011)

** Recorded only from one greenhouse (Leech, 1991)

 

Character Selection

The majority of characters and terminology used in this key were sourced from Ubick et al. (2017). For some couplets, several species (from multiple genera when possible) were examined by the authors to confirm trait consistency before using them to distinguish families. Some families include taxa that are exceptions to the typical family-level array of character states and were handled through additional couplets for those specific taxa. For Cheiracanthiidae and Desidae, characters were selected based on the single species in each family that has been recorded from the Prairie Provinces.

Photography & Line Illustrations

The majority of the photographed specimens are from the Arthropod Collection at the Northern Forestry Centre (Natural Resources Canada-Canadian Forest Service; NFRC). A few specimens were sourced from the E.H. Strickland Entomological Museum at the University of Alberta (UASM), the Royal British Columbia Museum, Victoria, BC (RBCM), and the Canadian National Collection in Ottawa, Ontario (CNC). All illustrations (photographs and line drawings) were made by the first author. All specimens were stored in ethanol and photographed in a dish filled with 75% ethanol. Spiders were photographed using a Dino-Eye AM7025X eyepiece digital camera (Dunwell Tech, Inc, United States of America, California) mounted onto the trinocular scope attachment of a Leica M205 C dissecting microscope. Spider specimens were positioned using a combination of glass beads and rolled up pieces of paper towel. In some cases, appendages were removed for ease of photography, but removal should not be necessary for the user to observe the majority of the illustrated features. Line illustrations were created using Affinity Designer (https://affinity.serif.com/en-gb/designer/) with the vector pen tool.

Post-Processing of Photographs

Images were stacked in Helicon Focus (http://www.heliconsoft.com/heliconsoft-products/helicon-focus/), using the depth map method. Photo stacks ranged from 15 to 300 individual images. Stacked images were then cropped and contrast-adjusted using Affinity Photo (https://affinity.serif.com/en-gb/photo/). In some cases, photos were edited using the ‘in-painting’ tool to remove glare from ethanol or floating material.

Anatomical Features and ‘Endpoint’ Pages

In addition to the key, illustrations of all anatomical features referenced within the key are provided (Plates 1-2). Whenever a new term is introduced in the key, a definition is provided again on the same slide, along with a corresponding illustration. The endpoint for any series of couplets terminating in a family identification is a ‘collage’ of photos for that family that includes a whole body photo of an exemplar from the family, a summary of important anatomical features, a list of internally hyperlinked characters that allow one to return to important couplets used in the determination, and numbers of species of that family recorded from each of the three Prairie Provinces as reported in Canadian Endangered Species Conservation Council (2016).

 

Plate 1

Plate 1. Key anatomical features (drawings).

 

Plate 2

Plate 2. Key anatomical features (photos).

Beta-testing

Beta versions of the key were tested by eleven individuals with varying levels of expertise. Three were trained in spider identification, two had some entomological training but little spider-specific knowledge, four were specialists of other invertebrate taxa, and three had no background in invertebrate taxonomy. Feedback from the testers was used to revise the key to improve clarity and ease of use.

Results

Outcomes of Beta-testing

The final key presented here was revised after multiple rounds of tester feedback. Individuals with no arachnological or entomological knowledge initially struggled with the key but were able to make correct determinations after reviewing the diagrams and restarting the key. Beta-testers had access to dissecting microscopes of variable quality. Only one tester experienced difficulties discerning character states on extremely small spiders, such as trichobothria (long, fine specialized setae) on members of Linyphiidae, a family of generally small spiders. Although insufficient magnification or poor resolution caused by inferior lenses can make identifications challenging, we expect that adults and juveniles in later stages of development from most families can be identified using the key in conjunction with the family-level collage pages.

Characters such as the number of tarsal claws (two vs. three) or the presence of specialized setae (e.g., the serrated comb on tarsus 4 in Theridiidae) are commonly used in traditional spider keys; to the novice, however, these are often challenging to see. In fact, one of the testers expressed difficulties in counting the number of tarsal claws, particularly when the specimen had very setose tarsi. In such cases, a leg can be removed from the spider, mounted on a slide using a temporary mounting medium such as clear corn-syrup or disinfectant gel, and examined with a compound microscope. If voucher specimens are needed, the appendage can be returned to an appropriately labeled vial with the rest of the spider afterwards. It is also helpful to know that in the Prairie Provinces, spiders with dense tufts of tarsal setae/scopulae are two-clawed (though not all two-clawed spiders have tufts/scopulae), while three-clawed spiders lack the tuft/scopula. The third claw is normally used for silk manipulation in weavers, while those that are two-clawed normally do not spin webs. There are 10 families of two-clawed spiders in the Prairie Provinces: Anyphaenidae, Cheiracanthiidae, Clubionidae, Corinnidae, Gnaphosidae, Liocranidae, Philodromidae, Phrurolithidae, Salticidae and Thomisidae.

Structure of the Current Key

To improve likelihood of a successful identification, some families key out in more than one couplet. For example, the family Tetragnathidae can be reached either by the exceptional length of their chelicerae (a state shown by most tetragnathid genera) or by endite characters in the case of Pachygnatha, which have shorter chelicerae than other Prairie Province tetragnathids (Álvarez-Padilla and Hormiga 2011). Early-instar juvenile tetragnathids can also have short cheliceral bases but will still key out as tetragnathids via the Pachygnatha couplet.

Whenever a new technical term is introduced in the key, a definition is provided on the same page. This should reduce the need to flip to the anatomical plates during the identification process. Another design choice was the avoidance of ambiguous wording (e.g., “relatively small”). When a feature is described in a relative context, it is described relative to another feature on the specimen itself using measurable parameters, such as “two times longer”. Characters were selected with the robustness of anatomical structures in mind. Delicate structures are not used early in the key. For example, the character “presence of trichobothria (fragile sensory hairs)” only appears towards the end of a series of couplets, and in most cases is the last character in the series. Like all CJAI keys, ours has the advantage of having an internally hyperlinked online version in addition to a printable version, which increases efficiency through link-clicking instead of page-flipping. Finally, the typical end-of-path pages containing a written diagnosis were replaced with pages containing habitus photos and ‘collages’ of the couplet photos that were required to reach the family-level endpoints, with couplet wording condensed to fit available space. These collages include links to source pages of the couplets in the key where the full wording can be checked. These family collage pages will allow users to confirm their identifications, or in the case of mistakes, significantly streamline backtracking. Characters considered vital to the characterization of the family are in bold font on the collage pages. The combination of the character-selection process employed and presence of the collage pages in this key should allow identification of juvenile specimens in later stages of development to family, with the exception of the family Mysmenidae and spiders in the genus Cicurina (Hahniidae), which require adult specimens. Identification of extremely young juveniles may not always be possible due to lack of sclerotization of relevant tissues, or very small size.

We hope our simple-to-use key will encourage more naturalists and ecologists based in the Canadian Prairie Provinces to use spiders in their studies.

Key to Families

Acknowledgements

We are grateful to the following curators and curatorial assistants for lending us specimens necessary for the completion of this key: Victor Shegelski UASM, Claudia Copley RBCM, and Owen Lonsdale CNC. We also acknowledge the contributions of beta-testers of the key (Shawn Abraham, John Acorn, Georgiana Antochi-Crihan, Philip Hoffman, Leah Jackson, Carina Lopez, Alessia Marchesan, Hannah Stormer, Aldo Rios Martinez, Cheryl Tebby, Hannah Whittal), who donated their time and provided relevant feedback that ultimately improved the usability of the key. Comments from Robb Bennet, Michael Draney and one anonymous referee greatly improved the clarity and consistency of our key.

References

Álvarez-Padilla, F. and Hormiga, G. 2011. Morphological and phylogenetic atlas of the orb-weaving spider family Tetragnathidae (Araneae: Araneoidea). Zoological Journal of the Linnean Society, 162: 713–879.

Bennett, R., Blagoev, G. and Copley, C. 2019. Araneae of Canada. Zookeys, 819: 41–56.

Bowden, J.J. and Buddle, C.M. 2010. Determinants of ground-dwelling spider assemblages at a regional scale in the Yukon Territory, Canada. Écoscience, 17(3): 287–297.

Bradley, R. 2012. Common Spiders of North America. University of California Press, Berkely, 288 pp.

Canadian Endangered Species Conservation Council (CESCC). 2016. Wild Species 2015: The general status of species in Canada [online]. National General Status Working Group. Available from http://wildspecies.ca/reports [accessed 20 March 2020]

Cárcamo, H., Pinzon, J., Leech, R., & Spence. J.R. 2014. Spiders (Arachnida: Araneae) of the Canadian Prairies. In: H.A. Cárcamo & D.J. Giberson (Eds.), Arthropods of Canadian Grasslands (Volume 3): Biodiversity and Systematics Part I. Biological Survey of Canada Monograph Series No. 5, Ottawa, pp. 75-137.

Cardoso, P., Pekár, S., Jocqué, R. and Coddington, J.A. 2011. Global patterns of guild composition and functional diversity of spiders. PLoS One, 6: e21710.

Dondale, C.D. and Redner, J.H. 1978. The insects and arachnids of Canada. Part 5. The Crab Spiders of Canada and Alaska (Araneae: Philodromidae and Thomisidae). Agriculture Canada Publication No. 1663, Ottawa, 255 pp.

Dondale, C.D. and Redner, J.H. 1982. The insects and arachnids of Canada. Part 9. The Sac Spiders of Canada and Alaska (Araneae: Clubionidae and Anyphaenidae). Agriculture Canada Publication No. 1724, Ottawa, 194 pp.

Dondale, C.D. & and Redner, J.H. 1990. The insects and arachnids of Canada. Part 17. The wolf spiders, nursery web spiders, and lynx spiders of Canada and Alaska. Araneae: Lycosidae, Pisauridae, and Oxyopidae. Agriculture Canada Publication No. 1856, Ottawa, 383 pp.

Dondale, C.D., Redner, J.H., Paquin, P. and Levi, H.W. 2003. The insects and arachnids of Canada. Part 23. The Orb-Weaving Spiders of Canada and Alaska : Araneae: Uloboridae, Tetragnathidae, Araneidae, Theridiosomatidae. Agriculture Canada Publication, Ottawa, 371 pp

Griffing, L. 2011. Who invented the dichotomous key? Richard Waller’s watercolors of the herbs of Britain. American Journal of Botany, 98: 1911–1923.

Lindroth, C.H. 1961-1969. The ground beetles (Carabidae, excl. Cicindelinae) of Canada and Alaska (Parts 2-6). Opuscula Entomologica, Supplement 20: 1-200; 24: 201-408; 29: 409-648; 33: 649-944; 34: 945-1192.

Leech, R. and Steiner, M. 1992. Metaltella simoni (Keyserling, 1878) (Amaurobiidae) new to Canada, and records for Tegenaria gigantea Chamberlin and Ivie, 1935, (Agelenidae) in Alberta and British Columbia (Arachnida: Araneida). The Canadian Entomologist, 124(2): 419-420.

Lowe, E.C., Threlfall, C.G., Wilder, S.M. and Hochuli, D.F. 2018. Environmental drivers of spider community composition at multiple scales along an urban gradient. Biodiversity and Conservation, 27: 829–852.

Paquin, P. and Dupérré, N. 2003. Guide d’identification des araignées (Araneae) du Québec. Fabreries, Supplément 11, 251 pp.

Pinzon, J., Spence, J.R., Langor, D.W. and Shorthouse, D.P. 2016. Ten-year responses of ground-dwelling spiders to retention harvest in the boreal forest. Ecological Applications, 26: 2581–2599.

Platnick, N. I. and Dondale, C. D. 1992. The insects and arachnids of Canada, Part 19. The ground spiders of Canada and Alaska (Araneae: Gnaphosidae). Agriculture Canada Publication No.1875, Ottawa, 297pp

Ubick, D., Paquin, P., Cushing, P.E. & Roth, V.D., eds. 2017. Spiders of North America: An Identification Manual. Second Edition. American Arachnological Society, Keene, New Hampshire, 425 pp.

Walter, D.E. and Winterton, S. 2007. Keys and the crisis in taxonomy: extinction or reinvention? Annual Review of Entomology, 52: 193–208

Wayland, M. and Crosley, R. 2006. Selenium and other trace elements in aquatic insects in coal mine-affected streams in the Rocky Mountains of Alberta, Canada. Archives of Environmental Contamination and Toxicology, 50(4):511-22.

World Spider Catalog (2022). World Spider Catalog. Version 23.0. Natural History Museum Bern, online at http://wsc.nmbe.ch, accessed on March 20, 2021. doi: 10.24436/2