Cannibalism in Fleas

It’s a flea-eat-flea world, and only the toughest survive into adulthood. 

It’s surprisingly tough being a flea. Environmental conditions play a big part in the survival of flea larvae – they require humidity of at least 50%, but ideally above 75% for optimal development. However, to make it to the adult stage they also need to avoid being eaten by other flea larvae!

Many will know that flea larvae eat flea ‘dirt’ – the faecal deposits of adult fleas, which contain a large amount of undigested blood. However, blood alone is an insufficient diet for the flea larvae to develop. Various studies have shown that no more than 33% of flea larvae fed on blood in flea faeces develop successfully into adults. So how do they top up their diet with the required nutrients to develop into adults?

It transpires that flea larvae eat flea eggs to develop successfully into adults. In one study, only around 10% of larvae fed on flea dirt alone developed into adults, whereas 90% of larvae successfully pupated when offered a diet of flea faeces and flea eggs. Interestingly, it is only the third-stage larval instars that eat the eggs, but they will eat in excess of 20 flea eggs before entering the pupal stage. But the threat of cannibalism returns when the flea enters this pupal stage.

Mature larvae spin a pupa of silk when they are ready to pupate. This pupa actually hardens clear, but as the exterior of the pupa is sticky, it picks up material from the surrounding substrate to create a cocoon. However, if the larva hasn’t eaten enough yeast during development, it will not be able to spin a cocoon. The flea can still develop into an adult as a ‘naked’ pupa, but it becomes susceptible to cannibalisation.

Third-instar larvae will readily consume naked pupae, but those developing inside cocoons coated in material from the surrounding environment are protected. These cocoons also allow the flea to remain dormant for several months after developing into an adult, if conditions are unfavourable. The adults from naked pupae will emerge immediately after development is complete.

As much as it’s interesting to know that fleas themselves deliver some level of population control through cannibalism, complete control can only be achieved through a thorough application of a professional flea treatment. High performing flea treatments use a combination of insecticide and insect growth regulator, such as Sumilarv. With its proven ability to impact all stages of the flea (even those ‘nasty’ third-stage larvae instars) and effectiveness at extremely low concentrations, Sumilarv helps deliver complete and long-lasting flea control.

 

Further reading: Rust, M.K (2017). The Biology and Ecology of Cat Fleas and Advancements in Their Pest Management: A Review. Insects 2017, 8(4), 118; https://doi.org/10.3390/insects8040118