Welcome to Blue Worms Composting, perhaps the internet's only site devoted to Perionyx excavatus (Perrier 1872). 

Perionyx Excavatus are a controversial worm in composting circles. They hail from tropical regions, particularly in the tropical areas around the Pacific Ocean. Common names for these worms are many; Malaysian blue worms, Indian blue worms, blues, PE's, California super red worms, among others.

PE's are rarely sold as composting worms in North America (largely because they’re temperamental) but can frequently be mixed into shipments of red wigglers (Eisenia Fetida) by invading commercial worm farm bins.

Most people that purchase worms are newcomers to composting with worms and are none the wiser. However one of a few things can happen when PE's are a part or majority of the mix,

1) The person is extremely successful at making compost and breeding worms.

2) The worms die on the floor beside the bin or when temperatures unexpectedly drop.

3) The worms constantly climb out of and escape the bin and frustration takes over and the person gives up. (seems much less frequent in cooler climates)

The key to surviving such a potential failure and potential frustration is in identifying perionyx excavatus and starting to understand their unique needs.

PE's are; in habitat needs very similar to eisenia fetida (EF’s) with ideal temperatures between 70F and 80F and moisture content between 70-80% however PE's are very athletic and active in comparison and are always likely to explore their habitat.

You do want to prevent the mass exodus from the bin they're so negatively reputed for. Watering a bin when dry should be done in morning if outdoors to allow the sun to keep them in the bin (mostly). These worms really like it dark but also like to be on the surface, so a layer of opaque material on top of the bin can keep them happier

Air flow is also an important factor in making sure they don't end up outside the bin like a pile of wet noodles, so adequate ventilation is crucial.


Perionyx excavatus are usually noticed fairly quickly by those more seasoned in composting with Eisenia fetida by their fast, twitchy way of moving and darker coloration. PE’s move in a manner not unlike an inch worm and most of their movement is concentrated in the front end while the rear appears drug along behind.

The clitellum on PE’s is also much closer to the head of the worm beginning at segment 13 rather than segment 24 or 25 on EF’s. Exposing a PE to a bright light will show a blue or purplish blue iridescence, hence the nicknames. The blue color is captured particularly well with digital photography when a flash is used in dim light.

What to Do After Discovering PE’s in Your Shipment

If you discover PE’s in your shipment of red wigglers you have a few choices:

  1. Take pictures and video, then contact the vendor and request a refund or return.
  2. Attempt to sort the worms (a daunting task)
  3. Learn to love them and design an escape proof bin.

Slowly lower temperatures below 48°F (9°C) but above 33.8°F (1°C) for 24 hours. This should kill PE’s and leave EF’s surviving. This will need to be repeated several times in 10 day intervals as cocoons may survive these temperatures.PE’s are voracious eaters and excellent composters if you can keep them contained. Part of this is due to their very fast breeding ability. Each adult is capable of about 19 to 24 cocoons/week with an 80% to 85% successful hatch rate. Cocoons hatch in 10-14 days in good conditions. Juveniles become sexually mature in as little as another 30 to 40 days.

Ideal Conditions for PE Growth and Breeding  Containing PE’s within a closed bin is generally the largest complaint with these worms. They are very adept climbers and are capable of stretching out very long and thin making it possible for them to go through tinier holes than what it would appear they would fit. Light is also much less a deterrent for them than for other species. The key seems to be in having some understanding of the climate to which they are indigenous. Being tropical they have evolved to survive heavy rains and monsoons. It would seem this may be a reason for their climbing ability.Most mass exodus of PE’s is reported to be during thunderstorms or heavy rains. All reports found to date also mention the worms climbing out the top of a bin & over the side. There are also cases documented of these worms being found in treetops and on top of tall buildings in a storm. Seriously limiting the upward avenues of escape seems to largely mitigate the mass escape that PE’s are legendary for. No holes or ventilation should be provided at the top of a bin built to keep PE’s and all airflow should be from lower portions of a bin as downward escape seems to not be an issue. Lids and covers on a bin should be very tight fitting, preferably with a gasket or weather stripping to seal them.


Receiving perionyx excavatus in a shipment need not end in failure or frustration, and can even be fun and productive. With their prolific breeding rate and voracious appetites one can compost a lot of waste in a short time and have a large mass of worms as well.


Population densities of about ½ pound (250 grams) to about 1 pound (500 grams) per 1 square foot (24 square cm) are ideal for breeding and should not exceed 2 pounds roughly 1 kg in that area to continue breeding. Higher densities can be tolerated for faster waste processing but worm breeding will be negatively affected.

As mentioned above ideal conditions for PE’s are similar to EF’s. A good starting point for breeding these worms is about 77°F (25°C) with 70% to 90% moisture in bedding of organic material (aged animal manure, leaf litter, cardboard, paper etc.