Charles McClintock from Sumitomo Chemical Australia gives an informative overview of flea larvae, plus tips for gaining control. 

Most people (and hopefully all pest managers!) would know what an adult flea looks like. However, the appearance and behaviour of flea larvae would be less well known and it’s important to understand this important life stage to ensure a comprehensive and successful flea treatment, especially as the larvae form around 35% of the flea population.

Flea eggs fall from the host animal shortly after being laid by the female flea. Within two days the egg will hatch, and a tiny translucent ‘worm’ will emerge. It is about 1.5 mm in length and will moult twice through three larval stages over a period of around 15 days, with the final larva being about 5 mm long.

Larvae feed on organic material, but to develop into adults they need to feed on ‘flea dirt’, the excess blood excreted by adult fleas. Their success in developing into adults is greatly enhanced by feeding on non-viable flea eggs, which are laid by virgin females. As such, flea larvae only thrive in sites that are regularly visited by the host animal, to provide a regular supply of flea dirt and eggs.

The larvae lack eyes and legs and have a thin translucent exoskeleton, through which their gut is visible. Their size and colour make them very difficult to see. It is their thin cuticle that makes them sensitive to environmental conditions. Humidity is a must for larval survival, with all larvae dying if humidity falls below 45%, and humidity above 60% being required for successful development. Larval development stops below 15ºC and they die when the temperature exceeds 35ºC for any length of time. As such, the coastal areas of Australia, particularly during the warmer months, provide optimal flea development conditions. Summer is the time of year when most flea infestations occur. The current La Niña conditions are ideal!

However, although flea larvae require high humidity, they don’t like high rainfall or wet soil. So, in outdoor areas, they only develop well in shaded, moist soils – under trees, verandas and decks, and in the sub-floor – just the same areas pets like to rest! When carrying out a flea treatment, these are the outdoor areas that require particular attention.

Indoors, the flea larvae hide in the carpet and cracks in the floorboards. Although they lack eyes, they are photophobic, rapidly wriggling away from light into the deeper layers of the carpet. As such, when carrying out a flea treatment it is important to ensure the treatment penetrates deep into the carpet and cracks.

Sumilarv, containing the IGR pyriproxyfen, has been proven to not just impact all life stages of the flea, but actually kill the larvae. With its long residual performance that prevents egg hatch for up to 12 months in carpet (Figure 1), and its effectiveness at extremely low concentrations, it’s a must for inclusion in any tank mix for flea treatments.

Chart showing residual control of fleas in carpet with Sumilarv
Figure 1: Residual control of fleas in carpet


But given that pet owners are understandably cautious about using insecticides around their ‘fur babies’, its great safety profile (unscheduled poison) means it is suitable as a standalone treatment for those pet resting areas, inside and out.

Back to articles on flea pest control and more information on fleas.


Charles McClintock, Professional Products Business Manager, Sumitomo Chemical Australia