What is the cornerstone physical feature used to distinguish katydids from true grasshoppers?

Answer

Antennae length relative to body length

The most reliable way to separate a katydid from a true grasshopper is by examining the antennae; katydids possess very long antennae, often significantly longer than their body, while true grasshoppers have antennae noticeably shorter than their body length.

What is the cornerstone physical feature used to distinguish katydids from true grasshoppers?
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