tail ▁with ▁a ▁dark ▁brown ▁glob ular ▁ab d omen ; ▁adult s ▁reach ▁a ▁length ▁of ▁around ▁. ▁There ▁is ▁often ▁a ▁" s now f la ke " - like ▁mark ing ▁on ▁the ▁ab d omen , ▁which ▁is ▁most ▁notice able ▁in ▁pal er ▁col oured ▁individuals . ▁The ▁mouth parts ▁are ▁internal , ▁and ▁the ▁head ▁be ars ▁a ▁pair ▁of ▁anten na e , ▁two ▁groups ▁of ▁eyes p ots ▁known ▁as ▁" com posed ▁eyes " ▁and ▁a ▁pair ▁of ▁small ▁post - ant enn al ▁org ans . ▁The ▁set ae ▁( br ist les ) ▁on ▁the ▁third ▁anten nal ▁segment ▁are ▁une qual ▁in ▁length , ▁some ▁being ▁much ▁longer ▁than ▁others , ▁and ▁the ▁fourth ▁anten nal ▁segment ▁is ▁divided ▁into ▁six teen ▁sub - seg ments . ▁There ▁are ▁three ▁th ora cial ▁segments , ▁each ▁bearing ▁a ▁leg , ▁and ▁five ▁ab dom inal ▁segments . ▁The ▁fourth ▁ab dom inal ▁segment ▁be ars ▁an ▁organ ▁known ▁as ▁a ▁" dens ", ▁and ▁at ▁the ▁tip ▁of ▁this ▁is ▁a ▁structure ▁known ▁as ▁a ▁" m uc ro ". ▁This ▁species ▁has ▁m uc ros ▁with ▁smooth ▁outer ▁edges ▁and ▁saw - ed ged ▁inner ▁edges . ▁In ▁females , ▁the ▁append age ▁on ▁the ▁fifth ▁ab dom inal ▁segment ▁is ▁unf ork ed . ▁ ▁Distribution ▁and ▁habitat ▁This ▁spring tail ▁is ▁native ▁to ▁Western ▁Europe . ▁It ▁is ▁common ▁in ▁the ▁British ▁Is les ▁and ▁inhab its ▁mo