Prosoma shape and araneophagy in Linyphiidae and other spider families (Arachnida: Araneae)

Adult males of linyphiid spider genera with a domed masculine prosoma shape and/or with a protuberance on the prosoma, showed a marginally significant higher killing potential (predation on spiders of various families surpassing the individuals of the killing genera in three body size measures) than did adult males of linyphiid genera possessing a flat prosoma shape. If the domed-prosoma linyphiid genera were statistically contrasted to the total of flat-prosoma linyphiid genera and non-linyphiid genera combined (non-linyphiid genera always characterized by a flat prosoma) the difference was highly significant, i.e. the adult domed-prosoma linyphiid males killed significantly more often spiders surpassing them in size than did the flat-prosoma adult males of linyphiid and non-linyphiid genera combined. It is hypothesized that the superior killing power of domed-prosoma genera is partly due to the domed shape of the prosoma. There may be factors closely linked with a domed prosoma that give a killing advantage to these genera, such as chelicerae morphology, behavioural manoeuvrability or killing technique, specific poisons, etc. We, further, hypothesize that the height of the dome (which was not included in measuring prosoma size) is not a decisive factor in killing advantage. If dome height would be a key factor, also the adult males of genera or species with an extreme dome height (like e.g. Entelecara acuminata) should have shown a high killing potential, but they did not. However, the adult males (and also often the adult females) of genera with a less extreme dome height, notably Walckenaeria and Gnathonarium, showed a very high killing potential, most clearly so Walckenaeria unicornis males and Gnathonarium dentatum females.