In the a recent Doctor Who episode, Arachnids in the UK, it is claimed that spiders never stop growing.

Is this true?

  • 1
    Is there a Dr Who tag? Should there be?
    – matt_black
    Oct 28 '18 at 21:38
  • 1
    I'm under the belief that insects as well as nearly all creatures with exoskeletons never stop growing. In fact, I'm under the impression that is the reason many of them die. Their organs cannot manage their size any longer. Probably a better question for biology.stackexchange.com.
    – fredsbend
    Oct 28 '18 at 23:45
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    @matt_black: No. We don't get many questions ABOUT the show, and we don't tag claimants.
    – Oddthinking
    Oct 29 '18 at 0:31
  • Related: Lobsters growing indefinitely
    – Oddthinking
    Oct 29 '18 at 0:32
  • 3
    @PaulJohnson The trouble with that is there are many apparently factual statements about the real world made in fiction and people do believe them. We should clearly ignore statements about the fictional world (so skeptical analysis of Dalek biology is clearly off topic).
    – matt_black
    Oct 29 '18 at 9:31

Tailless whip spiders (aka cave spiders or tailless whip scorpions) continue growing throughout their life:

No terminal molt takes place and so these animals grow all their life, but obviously the intervals between molts get longer in time. Both sexes have extremely elongated pedipalps, but the male's pedipalps are longer still.
Euphrynichus bacillifer

They molt once or twice a year until they reach maturity. Tailless whip scorpions continue molting and growing throughout their adult lives.
Phrynichus jayakari Whip Spider

The order Amblypygi includes ca. 150 species and 17 genera within five families. Amblypygids are dorsoventrally flattened chelicerates with prominent raptorial pedipalps and chelate chelicerae. They are also the only arachnid order that lack an ultimate (= terminal) molt (Weygoldt 2002). The anteriormost legs of amblypygids are antenniform, being extremely long and whip-like (hence their common name, Whip Spiders)
Ecology and natural history of the tree-inhabiting social amblypygid Heterophrynus batesii

  • 4
    This answer could need a picture. enters "Tailless whip spider" into image search. This answer does definitely not need a picture.
    – Philipp
    Oct 29 '18 at 13:08
  • 1
    @philipp They're harmless, you know. Cute, even.
    – fredsbend
    Oct 29 '18 at 14:54
  • Tailless whip spiders are large but they aren't ugly. I'd like to pet one some day. Oct 29 '18 at 17:02
  • @JohnDvorak you and I are on two different sides of the spectrum on that opinion. Petting them didn't quite make my bucket list.
    – PC Luddite
    Oct 31 '18 at 4:00

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