Thursday, 9 January 2020

On stridulation, and dictionaries...

Over the Christmas period I pulled out a few entomological and general science dictionaries to see how much bioacoustic terminology was present. The definitions of stridulation I found (with comments) are provided below, and there are some striking errors (at least for those who like their insects in the correct Order), as well as some minor issues.

The accuracy of the definitions seems to improve with the specificity of the work. The less likely you are to need the dictionary the more likely you are to have one with a correct definition?

A Glossary of Entomology (Torre-Bueno, 1962 third printing)

"stridulating organs, parts of the insect structure which are used in making sounds; in general, one part is a file-like area and the opposing one a scraper or rasp (Imms)."
"stridulation, in insects, the sound produced by rubbing one surface or one structure upon or against another, both being suitably roughened; the act of stridulating or making creaking sounds."
This definition seems concise and is hard to argue with.  

Oxford Dictionary of Science (4th Edition, 1999)

"stridulation The production of sounds by insects rubbing one part of the body against another. The parts of the body involved vary from species to species. Stridulation is typical of the Orthoptera (grasshoppers, crickets, cicadas), in which the purpose of the sounds is usually to bring the sexes together, although they are also used in territorial behaviour, warning, etc."
A major taxonomic issue here including the cicadas within the Orthoptera. Cicadas also produce sound by tymbalisation rather than stridulation. No note of the specialisation of the parts involved in sound production, but forgivable given the broad scope of the dictionary. Bonus point for mentioning the multiple purposes of sound production.

Henderson's Dictionary of Biological Terms (12th Edition, 2000)

"stridulating organs n. special structures on various parts of the body of certain insects such as grasshoppers, crickets and cicadas, which produce the characteristic "song" of these insects." 
"stridulation n. the characteristic sound made by grasshoppers, crickets and cicadas."
Again cicadas are a problem, although this time they are at least not placed within the Orthoptera. The specialisation of the structures is mentioned, although no mention of their movement against each other.

A Dictionary of Entomology (Gordh & Headrick, 2001)

"STRIDULATING ORAGNS Hardened parts of the insect body that are used in making sounds. Typically one part is a file-like surface and the opposing one a scraper or rasp (Imms)."
"STRIDULATION (Latin, stridulus = creaking, squeaky; English, -tion = result of an action. Pl., Stridulations.) 1. Friction of rigid parts on modified surfaces. Insects: The sound produced by rubbing a series of hard projections (spines, Acanthae) against a file-like surface, Stridulatory methods of acoustical communication are widespread in the Insect and probably the most generally used form of sound communication. Anatomy of a system consists of a Pars Stridens which forms a rasp (file) composed of tubercles and a Plectrum which forms a scraper (Strigil). 2. The act of stridulating or making creaking sounds."
This is about as comprehensive as one could expect in a dictionary. Not all stridulation in insects is by spines or tubercles, sometimes ridges on the integument are used, but this point seems relatively minor.