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Male weaponry in a fighting cricket.
Kevin A Judge1, Vanessa L Bonanno
1Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada. kevin.judge@utoronto.ca
Plos One
|December 25, 2008
Summary
Male field crickets possess larger heads and mouthparts than females, providing a significant advantage in aggressive contests. This sexual dimorphism in weaponry influences fighting success, particularly during intense physical combat.
Area of Science:
- Evolutionary biology
- Animal behavior
- Sexual selection
Background:
- Sexually selected male weaponry is common in nature.
- Field crickets (Gryllidae) are not typically known for sexually dimorphic weaponry.
- Male aggression in field crickets is relevant to both scientific study and cultural practices.
Purpose of the Study:
- To investigate sexual dimorphism in head and mouthpart size in the fall field cricket, Gryllus pennsylvanicus.
- To test if larger weaponry provides an advantage in male-male aggressive contests.
- To determine the relationship between weaponry size and fighting success.
Main Methods:
- Studied a wild population of Gryllus pennsylvanicus.
- Measured head capsule, maxillae, and mandible size relative to pronotum length.
- Conducted male-male combat experiments, matching pairs for body size or mass.
- Assessed fighting success, contest duration, and intensity.
Main Results:
- Male G. pennsylvanicus exhibit larger heads, maxillae, and mandibles than females, controlling for pronotum length.
- Males with proportionately larger weaponry won more fights.
- Increased differences in weaponry size enhanced fighting success, especially during grappling.
- Contest duration and intensity were not correlated with weaponry size.
Conclusions:
- The size of the head capsule and mouthparts are under positive selection due to male-male competition in field crickets.
- These findings provide the first evidence of weaponry-based sexual dimorphism and selection in field crickets.
- Results validate traditional Chinese knowledge regarding cricket fighting.
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