Size

Which is the biggest jumping spider species?

Short answer: Several, there are multiple species in the genera Phidippus (P. regius, P. otiosus, P. texanus, P. audax etc.) and Hyllus (H. diardi, H. giganteus) that reach similar sizes. All of them have significant variation in body length and size may appear unequal to the viewer due to differences in morphology.

Extended answer: Due to the sheer amount of Salticidae species (about 6000 present, numbers rising) the following list will mainly be focused on the large species, that frequently show up in the spider keeping hobby (Phidippus georgii, Phidippus tyrannus, Phidippus albulatus and Phidippus bidentatus excluded to remain the list more trivial).

To properly understand size in spiders, terms like size, size perception and variation have to be clarified.

Size: The size of spiders in scientific aspects is measured by the length of the prosoma („cephalothorax“) and opisthsomoa („abdomen“) combined, it neither includes the size of the chelicerae, nor the length of the spinnerets or legs.
Size contrasts strongly between spider genders. A phenomenon called SSD (sexual size dimorphism). This difference varies interspecifically, resulting in scenarios like the males of one species being larger than the males of a second species, while the females of the former being smaller than the ones of the latter species. This circumstance makes it impossible to conclude a certain maximum size of a species, without making it gender specific.

Size perception: Size perception may differ in different Salticidae. Contrasts in proportions and morphology could obfuscate the „real“ size of the spider (scientific measurement) and potentially lead to smaller spiders being perceived larger than reality.

Variaton
: Intraspecific variation is a big factor on size in spiders (Araneae).
Jocqué, 1981 states, that major size variations in the same instars of the same species appear to be the rule rather than the exception, ranges from 1 to 2 (twice the size) were not irregular.

The following lists shows some of the largest Salticidae species.
Selections for this list were made upon the criteria, that the spiders have to be members of the genus Hyllus and Phidippus (consesus about them being the two Salticidae genera with the largest members is widespread) and that they have to have documented body lengths of over 16 mm. The most recent data was chosen (to eliminate the factor of potential evolutionary size adaption).

Phidippus
Phidipps audax (Hentz, 1845)
♂ 8.39 mm, 15.24 mm / ♀ 10.93 mm, 18.10 mm (Edwards, 2004)
Phidippus otiosus (Hentz, 1846)
♂ 8.88 mm, 10.35 mm / ♀ 13.10 mm, 17.10 mm (Edwards, 2004)
Phidippus regius C.L. Koch, 1846
♂ 11.78 mm, 17.78 mm / ♀ 14.80 mm, 21.88 mm (Edwards, 2004)
Phidippus texanus Banks, 1906
♂ 11.53 mm, 15.36 mm / ♀ 14.40 mm, 20.04 mm (Edwards, 2004)
Phidippus octopunctatus (Peckham & Peckham, 1883):
♂ 11.17 mm, 13.91 mm / ♀ 14.92 mm, 18.87 mm (Edwards, 2004)


Hyllus

Hyllus diardi (Walckenaer, 1837):
♂ 15.50 mm (Peng et al., 1998)
♀ 17.28 mm (Basumatary et al., 2018b)



Note: The displayed measurements don’t claim to be the largest measurements of these species ever recorded, they are just measurement of examined specimen which belong to this taxon. The list may include other species in future just by new measurements of different specimens of already known taxa.

Sources:
-Jocqué, R. (1981). Size and weight variations in spiders and their ecological significance.

-Edwards, G. B. (2004). Revision of the jumping spiders of the genus Phidippus (Araneae: Salticidae). Occasional Papers of the Florida State Collection of Arthropods 11

-Basumatary, P., Das, S., Kalita, J. & Brahma, D. (2018a). New record of Hyllus diardi (Walckenaer 1837) (Araneae: Salticidae) from India. Acta Arachnologica 67(1)

-Peng, X. J. & Kim, J. P. (1998). Four species of jumping spiders (Araneae: Salticidae) from China. Korean Journal of Biological Sciences2