The world's fastest spider tops 3.5 metres per second

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  Evolutionary biomechanics of maximum running speed in spiders (Araneae)    Abstract Background Maximum running speed is a central performance trait, linking morphology, physiology and behaviour to fitness. It is shaped by physical capacity and ecological selection but may also be constrained by ancestry. To examine how these forces interact across macroevolutionary timescales, we conducted an allometric study in a hyper-diverse arthropod taxon—spiders (Araneae). Results Drawing on running performance data for 258 species from 64 of the 139 extant spider families, we integrated phylogenetic comparative methods and biomechanical modelling to disentangle the effects of body size, ancestry, leg morphology, ecological guild and preferred locomotor orientation. Maximum running speed varied substantially, both across body mass and among species of similar body mass. By accounting for body mass with a recent biomechanical model, we show that size-specific performance carries ...

Predation risk affects male activity and mating interactions with well-fed females in the wolf spider Pardosa milvina (Araneae: Lycosidae)

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Predation risk affects male activity and mating interactions with well-fed females in the wolf spider Pardosa milvina (Araneae: Lycosidae) 

Abstract

Courtship and mating behaviors are conspicuous and can attract eavesdroppers that pose a threat to both males and females. The body condition of females has significant effects on their reproductive output and so males should value well-fed females and be willing to take on increased risk in exchange for the opportunity to mate. We tested the hypothesis that predation risk affects male activity and mating behavior differently based on the female's body condition. We manipulated the body condition of female Pardosa milvina (Hentz, 1944) (Araneae: Lycosidae) and monitored the activity of males when placed on female substrate–borne cues with or without similar cues from their common predator, Tigrosa helluo (Walckenaer, 1837) (Araneae: Lycosidae). Males appeared to engage in a search for females on cues from well-fed females as they spent more time walking but covered less distance. Predator cues reduced this activity when coupled with cues from well-fed, but not food-limited females. In a second experiment, males were paired with females that differed in body condition and included treatments with and without predator risk. Females in good condition attacked males less and were more likely to mate. Males courted hungry females longer, but with the same intensity as well-fed females. Predation risk eliminated aggression toward males by well-fed females. In summary, males were able to identify the body condition of prospective mates from chemotactile cues alone, but when females were present, predation risk had little impact on the aspects of courtship and mating that we documented.

Ann M. Schlosser, Jill DeVito, Matthew H. Persons, Ann L. Rypstra "Predation risk affects male activity and mating interactions with well-fed females in the wolf spider Pardosa milvina (Araneae: Lycosidae)," The Journal of Arachnology, 53(3), 174-182, (25 February 2026) https://doi.org/10.1636/JoA-S-24-020