TT #175 · Parshas Shemini · Aliyah 5 · Passuk 31
Chabad.org — Vayikra Chapter 11 with Rashi
English: These are the impure among the swarming things; whoever touches them when dead shall be impure until evening.
Niddah 56a.
E-Daf.com — Niddah 56a (Tsurras Hadaf)
Textual analogy — “In their death” defines the physical condition required for the sheretz to convey impurity.
A sheretz conveys impurity while moist, but not when completely dry, because the Torah specifies a condition resembling death.