A Synopsis of the American Bats of the Genus Pipistrellus — Story, Setting & Ideas

Taxonomic Revision Based on New Material

The authors explicitly state that their main contribution comes from studying recently acquired Mexican specimens. P. cinnamomeus was previously known from a single specimen, and P. veracrucis from only six lost or misplaced specimens. By obtaining topotypes and additional material, Hall and Dalquest are able to clarify the relationships among these forms. They conclude that only two species occur in North America: P. hesperus in the west and P. subflavus in the east, with P. veracrucis reduced to a subspecies of the latter. This revision hinges on morphological comparisons, including measurements of total length, tibia, forearm, and skull dimensions.

Structure of the Species Accounts

Each species account follows a consistent format: synonymy, type locality, range, diagnosis, and remarks. The diagnosis for P. s. obscurus, for example, quotes the original description noting "color duller and less yellow, and dark tips of shorter hairs on back more conspicuous." The remarks section often acknowledges gaps in knowledge—for instance, the authors note that no one has carefully studied variation in P. subflavus since Miller named P. s. obscurus, and they admit that their assignment of specimens from Minnesota and Wisconsin to that subspecies is arbitrary because they have not seen them. This transparency about the limits of their evidence is a recurring feature.

Recurring Emphasis on Color and Dentition

Throughout the text, color and dental traits are repeatedly used to distinguish taxa. For P. s. veracrucis, the color is described as "much darker than that of P. s. obscurus" and placed between black and the darkest brown in Ridgway's color key. Dental features, such as the spacing of lower incisors and the presence of a basal cusp on the lower canine, are cited to differentiate specimens from Honduras. The authors note that in many P. s. veracrucis specimens, the upper tooth-rows are straighter than in P. s. subflavus, a detail that Rinker had described as "more convergent posteriorly." These precise morphological observations form the backbone of the taxonomic decisions.

Geographic Distribution and Gaps

The range descriptions and locality records reveal a patchwork of known occurrences. For P. subflavus, the authors list specific caves and counties, such as Cornwall's Cave in Pennsylvania and Symmes Creek in Ohio, citing earlier publications. They also note notable absences: the species has not been recorded from Michigan, northern Indiana, northern Illinois, or Iowa, though they suspect it occurs there. The distribution map, mentioned but not reproduced in the text, was prepared before two Wisconsin specimens were received, so those records are described verbally. This attention to gaps and provisional assignments underscores the tentative nature of the synopsis.

Readers should approach this synopsis as a snapshot of mid-20th-century taxonomic practice, where decisions were based on limited material and explicit acknowledgment of uncertainty. The authors' careful documentation of measurements, locality data, and bibliographic references makes the work a useful reference for historical distribution records, even if subsequent research has refined the classification. The concise format—just over 6000 words—allows for quick consultation of key diagnostic features and range information.

I’ve always found it curious how that old study on Pipistrellus bats, with its careful measurements of wings and teeth, whispers the same patient lesson as Natural History Or, Uncle Philip's Conversations with the Children about Tools and Trades among Inferior Animals — Themes and Context—that even the smallest creature shapes its own tools for living, quietly, without fuss, and we only need to look closely enough to notice.