The common name “daddy long legs” refers to a collective of distinct, long-legged arthropods often encountered in homes and gardens. Because this generalized label covers multiple species, determining the sex of a specimen requires first identifying the specific animal. The physical differences between males and females, known as sexual dimorphism, are unique to each group, allowing for accurate sex determination.
Addressing the Common Name Confusion
The creature commonly called a “daddy long legs” is usually one of three types: the Harvestman (Order Opiliones), the Cellar Spider (Family Pholcidae), or the Crane Fly (Order Tipulidae). The first step in sexing the animal is identifying which group it belongs to. Crane flies are the easiest to distinguish, as they are true insects with six legs, a distinct head, thorax, abdomen, and a pair of wings.
The two arachnid groups, the Harvestman and the Cellar Spider, are frequently confused but possess clear structural differences. The Harvestman has a body that appears as one fused, oval segment, lacking the constriction that separates the cephalothorax and abdomen. Harvestmen do not possess silk glands, meaning they never spin webs, and they lack venom glands.
The Cellar Spider, conversely, is a true spider with two distinct body segments connected by a narrow stalk (pedicel). These spiders are frequently found hanging upside down in their messy, irregular webs used to capture prey. Cellar spiders have venom, which is harmless to humans, and their ability to spin silk distinguishes them from the Harvestman.
Sexing the Harvestman (Opiliones)
Determining the sex of a Harvestman relies on observing specific morphological differences that vary by species. Females generally have a visibly larger, more rounded abdomen to accommodate the eggs they carry. Males tend to have a smaller, flatter body relative to their overall size, often presenting with longer legs in proportion to the body.
A more definitive method is examining the male’s chelicerae and pedipalps (the mouthparts and small, leg-like appendages near the mouth). In many species, the male exhibits specialized structures on these appendages, such as enlarged segments, horns, or tubercles. These features, used in territorial defense or courtship, are typically absent or much smaller in the female.
The most precise indicator, though difficult to see without magnification, is the presence of the reproductive organs. Unlike most arachnids, male harvestmen possess an aedeagus, an intromittent organ used for direct insemination. Females have a long, retractable ovipositor, which is extended only when the animal is ready to lay eggs into the soil or under a substrate.
Sexing the Cellar Spider (Pholcidae)
Sexing the Cellar Spider is most accurately accomplished by examining the pedipalps of a mature specimen. These two small, front-facing appendages near the spider’s fangs are the male’s copulatory organs. In adult males, the tips of the pedipalps are noticeably swollen, bulbous, or club-like in appearance.
These enlarged terminal segments, known as palpal bulbs, house the sperm before mating and are a reliable indicator of a mature male. Female cellar spiders possess pedipalps that remain slender and simple, closely resembling a short pair of additional legs. This difference is often visible to the naked eye.
Beyond the pedipalps, general body size serves as a secondary indicator. Male cellar spiders are often slightly smaller than females and have a less voluminous abdomen, as they do not house developing eggs. Females of common species like Pholcus phalangioides may reach about eight millimeters in body length, while males are slightly shorter at around six millimeters. The female’s abdomen may also appear distended if she is carrying a clutch of eggs, which she typically holds in a loose bundle with her chelicerae.