Spiders of North America Cover

Biological recording & species identification Other arthropods

Sarah Rose

Princeton University Press


ISBN: 9780691175614

Reviewed by Geoff Oxford

This very attractive and ambitious photographic guide covers some 500 of the more than 4,000 spiders known from North America. The layout of the book follows a standard pattern – indeed, I am not sure how one could structure it otherwise. A dichotomous key to the 12 extant arachnid orders found in the region (including horseshoe crabs) leads on to the separation of mygalomorphs from araneomorphs and then to anatomy and various aspects of spider biology. Under observation and field techniques it was good to see the inclusion of the late Mike Roberts’ spi-pot, the sonic toothbrush and a pooter (actually called a ‘pooter’, rather than the usual term in North America, ‘aspirator’). One trick we tend not to use over here is night collecting using a head torch. The beam reflects off the tapetum of spider eyes and the best angle for viewing is when the torch is secured below the nose; the technique is called ‘sniffing’! The introduction also includes several pages illustrating examples of different egg-sac morphologies and various spider enemies.

The main part of the book comprises species accounts, organised into eight sections, each covering a different guild of web-types or hunting techniques. For example, section 2 ‘The sensing web weaver guild’ includes spiders that use silk merely as a way of detecting that prey is nearby, rather than for actually detaining it. The families Atypidae and Segestriidae (both with British representatives) fall under this heading. Given that 71 families are included in the book, this makes an excellent and efficient way of ordering them into digestible segments and provides spider identifiers with a good framework from which to start homing in. However, it does rely for some guilds on observing web architecture, which will be missing if, for example, sweep-netting is used as a capture technique.

Each section begins with a dichotomous key to families. Unfortunately, photographs interspersed with the keys are often so small, despite enlargement of critical features, that differences may be difficult to discern. To some extent, this applies elsewhere in the book – a consequence of trying to squeeze so many species into one volume. Families follow the keys, with the nice idea of illustrating eye pattern configurations with different colours for the four eye pairings (anterior medians, posterior medians etc.), Genera within the family are given and the number of species in each provided. I was not convinced that the range of total body lengths, e.g., for the Theridiidae 0.8 – 12.0 mm, was especially helpful. A list of similar families, and how they differ from the one being considered, end the family overview.

Species accounts cover common names (if any), description, habitat and known records (based on states). A small but adequate map shows a broad-brush indication of where the spider might be found – the density of sampling for many species is low and so ranges are necessarily approximate. Naturally, I turned to species I know well, Enoplognatha ovata and E. latimana (Theridiidae), to check the adequacy of the accounts. Both have been recorded in North America for at least a century, probably introduced from Europe. Enoplognatha ovata is the more widespread of the two, occurring commonly on both the eastern and western coasts of northern USA and southern Canada. The map, however, suggests it occurs in every state of the USA, which I doubt. In the list of states with known records, ID, MI and OR are missing. There is, unfortunately, absolutely no mention of its look-alike congener E. latimana, which is common, and often found in mixed-species populations with E. ovata, on the western coasts of northern USA and southern Canada. Indeed, although the two are so superficially similar, it is possible to tell that the ventral view of a female ‘E. ovata’ (p.252, bottom left) is definitely of E. latimana. These Enoplognatha species could also be confused with Theridion californicum, which co-occurs in a western, coastal strip from British Columbia to southern California.

This highlights my major problem with this book; there is no indication of how many species are so similar that whole-body photographs are not adequate to distinguish them.  Without such cautionary knowledge, there will be a temptation to ‘shoehorn’ what one sees in the field into the limited selection of species offered on these pages. This is important because one of the aims of the book is to harness the observations of citizen scientists to improve our understanding of species distributions. This gripe aside, this is a lovely book and I take my hat off to Sarah Rose who single-handedly has accumulated and organised a tremendous wealth of information and images. It is an ideal aid for those wishing to narrow down the identity of the spider in their hand, although it is not clear whether it is intended for field use as it weighs in at nearly 1.3 kg.