Hair Shape

Lattke et al. 2018. Figure 1. Hair shape terms. A – subspatulate; B – linear; C – oblong; D – spatulate; E – ovate; F – reniform; G – lanceolate.

Lattke et al. (2018) - For describing hair shapes, the terms defined by Bolton (2000) are used as well as some botanical terms used for describing leaf shapes (Harris & Harris, 2001). Despite their origins in botanical morphology they are readily applicable to ant hairs. The following terms describe hair shapes:

clavate – club-shaped, with a cylindrical basal section and a swollen, but not flattened distal section. Similar in outline to a spatulate hair, but the latter is flattened.
lanceolate – lance-shaped, with the widest part basad (Fig. 1G).
linear – long and narrow, much more so than oblong, with parallel to subparallel sides (Fig. 1B).
oblong – flattened, two to four times longer than broad with parallel or subparallel sides (Fig. 1C).
ovate – egg-shaped, flattened, with the widest part basad (Fig. 1E).
reniform – kidney-shaped, flattened and widest close to midlength, the base is between two shallow convex lobes and the lateral and apical margins describe a broad convexity (Fig. 1F).
spatulate – elongate and flattened, gradually tapering basad with the widest part close to the apex (Fig. 1D).
subspatulate – similar to spatulate but with a lesser degree of tapering, not exactly oblong but not spatulate (Fig. 1A). Many of the descriptions and diagnoses describe outlines of particular body part margins; these (in particular the shape of certain teeth and hairs) are best seen by using reflected background lighting

Tang & Guenard (2023) document the variation in setal shapes within Strumigenys.

Tang & Guenard (2023), Fig. 1. Seta shape terminologies. 1. Fine. 2–3. Stout and truncated. 4–5. Plank-like. 6–7. Acicular. 8. Narrowly elliptic. 9. Elliptic. 10. Linear. 11. Short linear or short subspatulate. 12–13. Subspatulate. 14–15. Spatulate. 16–17. Oblanceolate. 18–19. Small obovate. 20. Large obovate. 21. Suborbicular/orbicular. 22. Orbicular. 23. Remiform. 24. Remiform / narrowly claviform (red arrow). 25–26. Claviform. 27. Shoehorn-shaped. 28. Spoon-shaped.

References

Bolton, B. 2000. The ant tribe Dacetini. Mem. Am. Entomol. Inst. 65: 1-1028 (page 1, Keys to world species)
Harris and Harris. 2006: Plant Identification Terminology: An Illustrated Glossary. Spring Lake Publishing, Spring Lake, UT, 206 pp.
Lattke, J.E., Delsinne, T., Alpert, G.D., Guerrero, R.J. 2018. Ants of the genus Protalaridris (Hymenoptera: Formicidae), more than just deadly mandibles. European Journal of Entomology 115: 268–295 (doi: 10.14411/eje.2018.027).
Tang, K. L., Guénard, B. 2023. Further additions to the knowledge of Strumigenys (Formicidae: Myrmicinae) within South East Asia, with the descriptions of 20 new species. European Journal of Taxonomy 907, 1–144 (doi:10.5852/ejt.2023.907.2327).