You might have noticed that bloodworms sold by different brands might come in different sizes,

or that the size of the bloodworms in the various bloodworm SKU's we market can even be different.

What causes this difference in body size?

 

LARVAL DEVELOPMENT STAGE

   As mentioned here bloodworms are the aquatic, larval life stage of non-biting midges and as such are holometabolous insects, meaning that these insects undergo different molts or life stages during their development. Larval midges go through four development stages before they turn into an adult (called an imago) and each stage is called an instar, with each consecutive instar larva being larger than the preceding instar larva. But not only the stage of larval development has an influence on the size of the larvae, environmental factors affect the size of the bloodworms as well.

WATER TEMPERATURE

   Insects are poikilothermic ectotherms, meaning that their body temperature is (almost) the same as the temperature of the environment. Generally said, the higher ambient temperature is, the faster the bloodworms will grow or develop. Naturally there exists a temperature above which the larvae will die whilst there also exists a lower limit under which the larvae will either stop feeding, either start to die off.

FOOD AVAILABILITY

   The presence of a large amount of food available to the developing larvae will be beneficial to the larvae and allow them to grow faster and larger.

FOOD QUALITY

   When rich food sources such as micro-algae and algae are available for the larvae, they will grow faster and become bigger compared to larvae able to feed only on detritus or other food sources having a low energy density.

COMPETITION FOR FOOD AND SPACE

   Chironomids have been reported in densities of several thousand larvae per square meter of pond or river bottom[1]. Such high densities might impact the body size of the developing larvae through restricting the amount of food or living space available to each larva.

VOLTINISM

   This term indicates the amount of generations a species produces in a year. Insects living in warm climates with plenty of food available may produce multiple generations in a year (multivoltine); when living conditions become less good they might produce 2 generations a year (bivoltine), a single generation per year (univoltine) or they might need multiple years for a single generation (semivoltine).

WATER QUALITY

   Chironomids are able to survive in eutrophied waters (waters polluted with a high amount of nutrients or organic matter) due to their strong ability of absorbing oxygen from waters having a very low amount of dissolved oxygen, but there exists a limit of course. When the amount of dissolved oxygen becomes very low, or when pH decreases too much, or when the amount of heavy metals or other chemical pollutants becomes too high, growth conditions for the larvae will decrease resulting in larvae having a smaller body size.

   The bloodworms we offer for sale are either instar 2, instar 3 or instar 4 larvae of the species Chironomus plumosus. Our bloodworms are not commercially grown or reared but are manually harvested from the muddy bottoms of slow-moving rivers and ponds. As such the bloodworms we process and sell are derived from multiple locations and are harvested throughout the year. During certain months only a certain size of larvae might be available at a certain location at the time, leaving us no choice as to process those bloodworms.

   Our mini-Bloodworms (SKU’s 88050 & 88051) always contain mostly instar 2 larvae, although some instar 3 larvae might be present. These are the smallest bloodworms we sell and can be fed to small fish, small-mouthed fish or juvenile aquatic amphibians.

 

   We also prefer using small-sized bloodworms for filling our Lunchbox blisters (SKU’s 20206 & 20207) and SKU 88054 (50 g blister-pack) due to the very small sized cubes of these blister-packs.

   All other bloodworm products we market mostly contain the larger instar 4 larvae although some instar 3 larvae might be present. However, should large bloodworms not be available during the time when our sales and inventory reports tell us to start processing additional amounts of bloodworms, we might have no other choice as to process small bloodworms and package these as regular bloodworms.