What do male and female fleas look like? - briefly
Male fleas are generally smaller and darker, with a slender, pointed abdomen; female fleas are larger, lighter‑colored, and have a noticeably expanded abdomen filled with eggs. The sexual dimorphism is most evident in the size and shape of the abdomen near the posterior end.
What do male and female fleas look like? - in detail
Male fleas measure 1.5–3 mm in length, possess a laterally compressed body, and exhibit a dark reddish‑brown coloration. Their heads are small, equipped with powerful mandibles for piercing host skin. Antennae consist of 16 segments, each ending in a sensory club. The thorax bears six jointed legs, each ending in a pair of enlarged, spiny ctenidia that enable rapid jumping. The abdomen is segmented, with a smooth dorsal surface and a ventral plate bearing the genital opening.
Female fleas are similar in overall size, ranging from 1.5 to 3 mm, and share the same dorsoventrally flattened shape and coloration. Distinguishing features include a broader abdomen to accommodate egg development and a slightly longer, more tapered posterior segment. The genital aperture is positioned ventrally near the terminal abdominal segment, and the ovipositor is visible as a subtle, elongated structure. Leg morphology mirrors that of the male, with the same jumping adaptations.
Key morphological differences:
- Abdomen shape: females have a more expanded, rounded abdomen; males display a slimmer profile.
- Posterior segment: females possess a longer, tapered terminal segment; males have a shorter, rounded terminus.
- Genital structures: males exhibit a visible aedeagus and associated claspers; females show an ovipositor and larger ventral opening.
Both sexes retain the flea’s characteristic combs (genal and pronotal), which consist of stiff spines used for anchoring to the host’s fur. The exoskeleton is hardened with chitin, providing resistance to abrasion during rapid jumps. Eye development is minimal; most species have simple, ocelli‑type eyes that detect light intensity rather than form. These anatomical details enable identification of sex in field and laboratory settings.