Jumping spiders belong to the family Salticidae, one of the largest groups of arachnids, known for their powerful eyesight and agile, non-web-building hunting style. They are often observed in gardens or kept as pets, prompting many observers to wonder about their sex. Distinguishing between a male and a female involves focusing on specific anatomical and behavioral differences that develop as the spider matures. Once these differences are understood, reliable identification becomes clearer.
General Visual Distinctions
One of the most immediate indicators of a jumping spider’s sex is its overall body shape and size, though this is not always definitive. Female jumping spiders typically exhibit sexual dimorphism, possessing a larger, more robust, and bulkier body structure than their male counterparts. This size difference is particularly apparent in the abdomen, which is often plump and rounded in the female to accommodate egg production.
In contrast, the mature male is usually smaller and more streamlined, often described as having a compact or elongated, torpedo-like appearance. The male’s smaller abdomen is generally more slender and does not expand significantly past the width of its cephalothorax. This more agile build supports the male’s need for activity and movement when seeking out mates.
Coloration and patterning also frequently differ between the sexes, particularly in popular species like the Regal Jumping Spider (Phidippus regius). Males often display a striking, high-contrast appearance, such as a deep black body with bold markings or iridescent scales used in courtship displays. Females tend to have a wider variety of colors, including muted shades of brown, gray, orange, or white.
A more detailed visual clue lies in the spider’s chelicerae, the hardened mouthparts that hold the fangs. In many dimorphic species, the chelicerae of the male are noticeably more pronounced and may feature a brilliant, iridescent coloration. The female’s chelicerae, while still functional, are typically smaller and may be colored with a softer pink, rose, or copper tone.
The Role of Pedipalps and the Epigynum
The most reliable method for determining the sex of a mature jumping spider involves examining the primary sexual characteristics located on the front and underside of the body. These features offer definitive proof of sex once the spider has completed its final molt into adulthood. For males, this distinction is visible in the pedipalps, which are the two small, leg-like appendages situated near the mouth.
In a mature male, the tips of the pedipalps become noticeably enlarged and bulbous, resembling small “boxing gloves” or mittens. These structures contain the copulatory organs, which the male uses to transfer genetic material to the female during mating. If a spider possesses these distinctive, swollen palpal bulbs, it is a mature male.
A mature female lacks the enlarged pedipalps but instead develops a specialized structure called the epigynum. The epigynum is a small, hardened plate or slit located on the ventral side (underside) of the abdomen, just forward of the cephalothorax joint. This structure is the external opening of the female’s reproductive tract, designed to receive the male’s pedipalps during copulation.
Identifying the epigynum typically requires close observation, often with the aid of magnification, such as a jeweler’s loupe or a macro photograph. It often appears as a small, dark, and shiny spot or a defined, smooth plate against the hairier texture of the abdomen. Note that both the enlarged male pedipalps and the female epigynum are only fully developed after the spider reaches sexual maturity.
Behavioral Clues and Maturity
Observing the spider’s behavior can provide supplementary information that confirms the physical evidence of its sex, particularly concerning activity levels and courtship rituals. Mature male jumping spiders are significantly more active and exploratory than females, driven by the instinct to seek out and locate mates. They often move restlessly around their environment.
When a male encounters a potential mate, he performs an elaborate, species-specific courtship display, often involving intricate leg and pedipalp movements, resembling a complex “dance.” The female’s role in this interaction is more passive, evaluating the male’s display and choosing whether or not to allow mating. Females who are not receptive may respond with aggressive or defensive posturing.
Another subtle behavioral difference involves the use of silk retreats, often called hammocks. While jumping spiders do not build webs for catching prey, they do construct dense silk sacs for molting and resting. Females will construct thicker, more substantial silk retreats, which are later utilized as protective egg sacs after successful mating.
Because definitive sexual characteristics only appear after the final molt, attempting to sex a juvenile spider based on size or color is unreliable. Behavioral cues and secondary physical characteristics are best used to support the primary anatomical evidence in a fully grown specimen.