10 Little-Known Facts About Fleas

Human fleas can jump a distance of 33 cm. That’s 200 times their body length. And amazingly, female cat fleas can drink 15 times their weight in blood a day.

The above tidbits are interesting, but they are commonly cited and can be found everywhere. In this article, I will cover 10 lesser-known facts about fleas. Hopefully you haven’t heard some of these before, and will come to further appreciate how fascinating fleas are!

#1 Some Adult Fleas Poop in the Mouths of Larvae

Larvae of the northern rat flea, Nosopsyllus fasciatus, will actively seek out adults and grab them with their mandibles. The seized adult then responds by defecating until the larva releases its hold and goes to consume the feces. Alright, the adults don’t actually poop directly in the larvae’s mouths. That was a bit of a sensationalist title. I had to start strong.

The cat flea, Ctenocephalides felis, is the most common species found on dogs and cats. Cat flea larvae will also feed on fecal blood from adults. However, the larvae graze for this feces in their environment. Sadly, cat flea larvae don’t share the same special bond with adults that rat fleas do.

#2 Fleas Inhabit Every Continent on Earth

Fleas have a cosmopolitan geographic distribution. They can be found on all the world’s continents and on most oceanic islands. Even Antarctica has a species of flea, Glaciopsyllus antarcticus, which parasitizes seabirds. The sub-antarctic islands also have fleas that feed on a variety of seabird species. There’s no where to run to from fleas!

#3 Fleas can Parasitize Ticks

One species of flea, Coptopsylla lamellifer, has been observed to accidentally use ticks as hosts, feeding on their haemolyph (circulatory system fluid). This rare type of feeding has been termed “heterovampirism”. “Homovampirism” would be the term used if fleas fed on other blood-engorged fleas of the same species (fleas don’t, but some ticks do)..

Fleas almost exclusively parasitize mammals and birds. The majority of flea species are parasites of mammals, with only around 3% to 5% of species considered specific bird parasites. Sometimes flea may accidentally feed on reptiles as well.

#4 The Origin of Fleas

It is believed that fleas originated from the Lower Jurassic period. Later, in the Eocene period, fleas began to rapidly evolve when the diversification of mammals exploded. Flea fossils are very rare, but those discovered in amber date back to the Upper Eocene and Miocene periods.

#5 Adult Fleas Walk More than they Jump

Fleas are well-known for their incredible jumping abilities, however, their main type of locomotion is walking. This is especially true for cat fleas, which become permanent residents of their host.

Adult fleas have a laterally-compressed body, a narrow head, and flexible joints of the thorax and abdomen. These physical adaptations allow fleas to easily traverse through a host’s pelage by dividing the hair during forward movement. The front of some fleas is covered with a large number of pores. These pores release an oily substance onto the surface of the flea to help facilitate movement through the host’s hair.

#6 Animals Sanitize and Fumigate their Nests for Fleas

The whistling rat, Parotomys brantsii, has been observed to replace old bedding from its burrow with new material. This is thought to be a strategy to remove fleas (and other parasites) from the burrow. European badgers also exhibit similar behavior. They will ‘air out’ their bedding material periodically by bringing it to the surface and exposing it to sunlight.

Some species of birds are known to incorporate fresh, green herbs into their otherwise dry nest material. They seem to prefer plants with aromatic, volatile compounds. Researchers believe these plants may be used as a bactericide, insecticide or repellent. Mammals also engage in similar behavior. For example, badgers will bring plant materials with biocidal or fumigant properties into their nest.

#7 The Ancestor of Fleas

One theory regarding the origin of fleas suggests that its early ancestor was a winged boreid-like insect (snow scorpionfly). This insect was free-living and scavenged for food in snowy and mossy habitats. At some point, it began seeking food in animal burrows. Eventually it adapted to parasitism to feed directly from the animals it once scavenged from. Its body became laterally flattened and it obtained mouth-parts for piercing skin and sucking blood. Over time the insect lost its wings, but maintained some semblance of flight with its jumping ability.

#8 The Feeding Habits of Ground Squirrel Flea Larvae

Oropsylla alaskensis is a species of flea that is parasitic to ground squirrels. The adult females will only lay eggs once the host has begun hibernating. Once the larvae hatch, they will migrate to the squirrel’s oral cavity. There, the larvae pierce the rodent’s tongue and gums and feed on the blood. That doesn’t sound like a pleasant nap.

#9 The Mechanism Behind Flea Jumps

Fleas’ incredible jumping ability is derived from the power generated by muscles of the hind legs and a rubbery protein called resilin. When the resilin is stretched and then relaxed, it releases around 97% of its stored energy. The release of this energy is a purely physical process, unlike muscle contraction which relies on chemicals. As such, air temperature is of little consequence to a flea’s ability to jump.

#10 Not All Fleas are Good Jumpers

Fleas are believed to have co-evolved with their hosts. As a result, the locomotion patterns of different flea species are believed to be adapted to the ecology and habits of their preferred host. For example, fleas which live off-host within nests, fleas of flying hosts, and fleas of desert rodents are all extremely poor jumpers. This is especially true with fleas that parasitize bats, as they rarely jump at all.