I’m about half-way through the “Opiliones Project” – this is a twitter-project devoted to sharing facts about Harvestmen (follow using the hashtag #OpilionesProject).  As I was working through some of the chapters, I gave a lot of attention to the variety of common names given to Harvestmen, including Daddy Longlegs.  This is not a very good common name for Opiliones because the characteristic of ‘long legs’ is not common to all Harvestmen, and many species (especially in tropical regions) are rather stout and don’t have the long, dangly, legs that we often associate with Opiliones in more northern regions.

The other reason to avoid the name daddy longlegs for Harvestmen is because of the confusion it creates with respect to a distant relative of Harvestmen – a spider with the latin name of Pholcus phalangioides.  This species is often referred to as the “Daddy longlegs spider” (and, by the way, the name “Phalangida” has historically been used as a synonym to Opiliones – more confusion!).   The rather obvious similarity between northern Harvestmen and Pholcus phalangioides is that they both have long legs – but it stops there.  Spiders have a narrow waist (i.e., the constriction between the cephalothorax and abdomen) whereas Harvestmen do not.  Pholcus phalangioides is also an enthusiastic web-builder whereas Harvestmen do not live in webs.  Here’s a photo of Pholcus phalangioides, courtesy of Ashley Bradford. (thanks, Ashley, for permission to use your photograph!)

A cellar spider, with prey (c) A. Bradford

Comparing a Spider to a Harvestmen is like comparing a blue whale to a chimpanzee.  Spiders are a different order (Araneae) than Harvestmen (Opiliones), and although both Arachnids, they diverged millions of years ago.  Opiliones are more closely related to Scorpions, Pseudoscorpions, and Solifugids than they are to the Araneae.

The other common name for Pholcus phalangioides is the “cellar spider” and this is much more appropriate – these spiders are synanthropic (see my other posts about spiders that like living in or near your home, the zebra spider & the ceiling spider), and are very commonly found in dark, damp places in and around human structures.  In my own house, the garage and basement are the common habitats.   Pholcus phalangioides is very distinctive – in addition to its long legs, it is a fascinating species from a behavioural perspective – if disturbed, it gyrates and whirls around in an impressive display of arachno-energy.  This is something I encourage you to try with your own populations of the species – it is wonderful to watch.  This behaviour is very well documented on youtube.  For example….

Wikipedia has an interesting entry about Pholcus phalangioides – including mention that one of its other common name is the “skull spider” because of patterning on its abdomen.  I also learned that the television show “Mythbusters” did an episode (in 2004) devoted to this species!   They busted the myth that this species had potent venom, but was unable to to pierce human skin (you can watch some of that episode here).

There has been some high quality research done on Pholcus phalangioides.  A nice overview of the biology of the species was provided by Jackson & Brassington, in 1987 – their paper is a key source for taking you back to the older literature on the species, and they also provide evidence that Pholcus phalangioides is an aggressive mimic of other spiders, and they are araneophagous (i.e., eat other spiders).  More recently,  Schafer and Uhl, in 2002, focused on mating behaviour and the role of male “pedipalp movements” as predictors of paternity in the species.  Bernhard Huber has recently (2011) written about the phylogeny and classification of the family Pholcidae and provided an updated cladistic analysis.

Keep an eye out for these characteristic spiders and don’t confuse them with the Opiliones…and be careful using the common name of Daddy Longlegs – it means different things to different people.

References:

Jackson, R.R. & R.J. Brassington. 1987.  The Biology of Pholcus phalangioides – predatory versatility, araneophagy and aggressive mimicry.  J. Zool. 211: 227-238. http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7998.1987.tb01531.x/abstract

Huber, B. (2011). Phylogeny and classification of Pholcidae (Araneae): an update Journal of Arachnology, 39 (2), 211-222 DOI: 10.1636/CA10-57.1

Schäfer, M., & Uhl, G. (2002). Determinants of paternity success in the spider Pholcus phalangioides (Pholcidae: Araneae): the role of male and female mating behaviour Behavioral Ecology and Sociobiology, 51 (4), 368-377 DOI: 10.1007/s00265-001-0448-9