Daddy long legs

The phrase 'daddy long legs' illustrates one of the biggest problems in biology. That is, people in different parts of the world use the same name to refer to more than one species or even groups of species.

In the case of 'daddy long legs' this name is used to refer to one of three different invertebrates:

  1. A true fly belonging to the family Tipulidae. These flies are also sometimes called Crane flies.
  2. A type of arachnid related to spiders known as an Opilione or sometimes as a harvestman.
  3. A species of spider called Pholcus phalangioides which is found in cellars, basements and dark corners of houses. It's also called the Daddy Long Legs spider or Cellar spider. Interestingly this spider is also a subject of an urban myth that says it has the strongest venom of any spider in the world but that its fangs are too small to penetrate the skin of a human. This is a myth, the venom is relatively weak... and they can pierce the skin (just).

Entomologists and other scientists remove this ambiguity by using the scientific name for an organism. This name is the same across the world so scientists can be sure they are talking about the same species.

A close-up photograph of a daddy Long legs (tipulid).

A tipulid fly.
Photograph by Eugene Zelenko, used under GFDL

A photograph of a harvestman.

A photograph of a harvestman.
Photograph by Martina Tillein licensed under Creative Commons.

A photograph of the cellar spider (_Pholcus phalangoides_).

A photograph of the cellar spider (Pholcus phalangioides).

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