cer·cus 
(sûrkəs, kĕr-)
(sûrkəs, kĕr-)n. pl. cer·ci (sûrsī, -kī, kĕrkē)
Either of a pair of appendages located near the tip of the abdomen in many insects and certain other arthropods, usually having a sensory function.
[New Latin, from Greek kerkos, tail.]