Transcript:

Today on Animal Fact Files we’re discussing lice. There are over 5,000 describing living species of these parasites and likely many more to be described. Lice are called “permanent ectoparasites” because they spend their entire life on a single host - often on a single individual host. There is not a free living stage elsewhere in the environment. Though it should be noted that human lice are special because they can live in textile fibers which means they can be alive in our environments. Aren’t we lucky?

Lice are found only on birds and mammals though sometimes they hitch rides on insects to travel between hosts. The lice we’re discussing today are known as “true lice” and are separated from other animals known as lice, like booklice, because they lack wings. Since they lack the ability to move between hosts, lice remain on the same host for their entire lifecycle. This is why they may utilize other animals for transportation between hosts. The only other way they can move is for one host to come in close contact with another host of the same species. Lice can be so specific to a certain species that if that species goes extinct, the lice will too! There are also general lice like one species which can be found on all types of gulls.

Wherever mammals and birds live, lice live there, too. However, some animals have managed to avoid these parasites. Of note bats, moles, monotremes, and whales - including dolphins - lack lice. Animals known as “whale lice” aren’t actually lice but a type of crustacean. Many lice are species specific and parasitize a single species - often a single spot on that single species. For example, one louse species may be on a bird's wings, another on the neck, and another on the back. It’s the same with human lice. The crab louse prefers the coarse hair in armpits and the genital region while head lice prefer finer head hair. These are different species!

Lice are tiny, reaching less than half an inch long in the largest species, though they’re often much smaller than this. They go through incomplete metamorphosis where nymphs hatch from eggs, go through three instars, and develop into adults. Lice have separate sexes and reproduce sexually, though asexual reproduction through parathenogensis has been observed. Eggs, which are called ‘nits' are glued to hair or feathers. These hatch about a week later depending on the surrounding temperature. Lice eggs hatch based on the host’s body temperature. The nymphs spend a week developing into an adult that may live up to a month on the host.

Historically lice were separated into the chewing and sucking lice, but they’ve since been grouped together taxonomically speaking. Still, there are lice that eat hair, skin, and oil from the host, sometimes taking blood with their chewing mouthparts; and then there are sucking lice with a piercing mouth that goes through the skin to draw up blood. Many lice have reduced eyes or no eyes at all, they also have large claws that help them hold on to a host's individual hairs. In the wild, you might see birds taking dust baths to rid themselves of these parasites, so the lice have to be able to hold on tight!

For more facts on lice, check out the links below. Give a thumbs up if you learned something new today. Thank you to our Patrons SpikeSpiegel93, Dad, and everyone else for their support of this channel! Thank you to dqw for today’s request! And thank you for watching Animal Fact Files!