How do different fleas look? - briefly
Fleas range from 1 mm to about 4 mm; darker brown specimens have a broader, laterally flattened body and longer hind legs, whereas lighter-colored individuals are smaller with shorter legs. All species possess distinctive comb‑like spines on the head and pronotum that secure them to host fur.
How do different fleas look? - in detail
Fleas exhibit a compact, laterally flattened body that facilitates movement through the hair or feathers of hosts. Size ranges from 1 mm in the cat flea (Ctenocephalides felis) to 4 mm in the rat flea (Xenopsylla cheopis). Coloration varies among species: the cat flea is reddish‑brown, the human flea (Pulex irritans) appears dark brown to black, while the dog flea (Ctenocephalides canis) shows a lighter, yellowish hue.
Key morphological features differ as follows:
- Head: Small, with large compound eyes and a pair of antennae concealed beneath the frons. The mouthparts form a piercing‑sucking stylet capable of penetrating the host’s skin.
- Thorax: Robust, bearing six legs adapted for jumping. The hind legs are especially enlarged, with a spring‑like resilin pad that stores elastic energy for rapid propulsion.
- Legs: Each leg ends in a pair of claws that grip hair shafts. The tibiae possess comb‑like spines (genal and pronotal ctenidia) that aid in moving through fur and preventing dislodgement.
- Abdomen: Segmented, soft, and expandable to accommodate a blood meal. The dorsal surface often bears fine setae that give a silky sheen; ventrally, the abdomen tapers toward the anus.
Species‑specific variations include:
- Cat flea – smooth dorsal cuticle, prominent genal comb, pale to dark brown coloration, average length 1.5–2 mm.
- Human flea – darker exoskeleton, reduced or absent genal comb, slightly larger body (2–3 mm), broader abdomen.
- Rat flea – elongated body, pronounced pronotal comb, deep brown to black coloration, length up to 4 mm.
- Pygmy flea (Tunga penetrans) – tiny (0.5 mm), rounded body, reduced legs, adapted for burrowing into skin rather than jumping.
The exoskeleton is composed of chitin, providing rigidity while allowing flexibility at joint membranes. Respiratory openings (spiracles) are located on the thorax and abdomen, each surrounded by a protective plate. The flea’s sensory setae detect vibrations and heat, guiding host location.
Overall, flea morphology reflects adaptations for ectoparasitism: a flattened profile for navigating host integument, powerful hind legs for leaping distances up to 100 mm, and specialized mouthparts for efficient blood extraction.