What do flea pupae look like?

Summary

Flea pupae closely resemble adult fleas. Pupae have compressed bodies, no wings, inconspicuous eyes, short antennae, and elongated piercing mouth parts. Their legs and appendages are free from the body wall (exarate pupae). While pupating, the pupae transition from white to yellow to brown. Flea pupae are rarely visible, because most larvae pupate within cocoons. However, sometimes ‘naked pupae’ develop without cocoons.

Details

What Flea Pupae Look Like

Color

After larvae molt into pupae, they remain white for 5-9 days. Then they become yellowish for 2-3 days. Finally, the pupae darken into a brown color. Combs and bristles turn black a day or two into the brown stage. When they’re ready to emerge, the pupae are nearly as dark as adult fleas. These color changes occur on the underlying adult cuticle. The pupal cuticle remains colorless.

image of a flea pupae in its cocoon

Img 1: A cat flea cocoon torn open to reveal a young, white pupa inside.

photo by: Auguste Le Roux

Size

Mature larvae are 4-5 mm long, and 0.5 mm wide. Prior to pupation, they fold themselves in half. A doubled-over, U-shaped larva measures 2.5 by 1 mm. While pupating, the larval head and last three body segments are lost. The flea body then slightly shortens and widens. The folded larvae has some space to spare within the cocoon. After pupation, there is considerable space unoccupied.

Flea pupae are about the same size as adults, 1.5 to 3.2 millimeters in length. However, the cocoon structure adds to their size. Cocooned pupa are 4-5 mm long, and 2 mm wide.

Body Shape

Tissue Reorganization

As a larva transitions into a pupa, body tissues are broken down and reorganized. The immature flea withdraws into its center. As a result, the head, prothorax, and last three abdominal segments become semi-transparent. The future pupa resides in the remaining opaque, creamy-white area, from the mesothorax to the sixth abdominal segment. The pupal head develops from the larval prothorax and mesothorax.

6-12 hours before the larva molts, fluid from its last 3 segments gets absorbed. The segments then collapse. Fluid disappears from the anterior parts soon after, but the rigid head capsule doesn’t collapse. A pupa emerges from the old larval cuticle 3-8 hours after the posterior segments collapse.

Shape

Shortly after shedding the larval cuticle, the pupa’s body gradually shortens and widens. While turning brown, the pupal musculature is transformed to the adult structure. As a result, the brown pupa assumes a dorsally humped posture. Flea pupae have the same general shape as adults. Pupae have a compressed body, no wings, inconspicuous eyes, short antennae, and elongated piercing mouth parts.

Appendages

Fleas have exarate pupae, meaning their legs and appendages are free from the body wall (obtect pupa have appendages fused to the body wall). They resemble adults, with legs folded up next to their body. 2-24 hours before molting into adults, the legs break away from their close position on the abdomen.

dark brown flea pupae

Img 2: A mature flea pupa in the brown stage. Flea pupae legs are free from the body (exarate pupa).

photo by: Auguste Le Roux

Pupal Cuticle

The pupal cuticle acts like a sheath, holding the legs and body in position until the adult emerges. Mouthparts are also contained in pupal sheaths. As adults emerge, the feet are the last body parts to leave the cuticle. The “pupal socks” soon get rubbed off against the cocoon wall. All the shed larval and pupal casings remain inside the cocoon.

Cocooned vs Naked Pupae

Most flea larvae pupate within camouflaged cocoons. However, not always. Those pupating without cocoons are termed ‘naked pupae’. Naked pupae develop when there’s not a nearby physical object, or vertical surface, to attach silk threads to. Naked pupae also occur if the larval substrate is shaken during cocoon formation. Around 50% of disturbed larvae will abandon their cocoons. They’ll even vacate fully formed cocoons, as there’s an 18 hour window before pupation begins.

naked pupae

Img 3: Cat flea pupa without a cocoon (naked pupa).

photo by: Auguste Le Roux

picture of flea cocoons

Img 4: Cat flea pupae within camouflaged cocoons.

photo by: Marcelo de Campos Pereira

The cocoon isn’t necessary for survival. Naked pupae still successfully pupate into adults. However, the adults can’t enter into a quiescent, pre-emerged state without a cocoon. Additionally, naked pupae are easier to vacuum from carpets than cocooned pupae. The cocoon also protects pupae from cannibalizing larvae.

References

Have an unrelated question?

ask a question

Discussion

Top