Collembola are also known as snow fleas or springtails. They are very small arthropods, generally measuring two to three millimeters in length, with some reaching one centimeter. They have highly variable colouring: red, blue, orange, yellow, pink, etc. They have four-segment antennae on their heads and from one to eight simple eyes grouped into a mass on each side, giving the impression of two distinct eyes. They are always apterous (wingless). Their abdomen has only six segments and carries the collophore and furca (or furcula). The collophore is used to suck liquids, to maintain bodily water balance, and plays a role in respiration. In the aquatic members of the species, the collophore facilitates adhesion to the surface of the water and stabilizes the individual in the wind. It is this organ that explains the group’s scientific name: ‘kola’, which means adhesive, and ‘embolos’, meaning plug or anything inserted. The furca is a forked appendage folded under the abdomen and held in place by the retinaculum (little hook); it acts as a spring and is used to propel the individual into the air. The furca also enables it to escape from predators. Thanks to this appendage, Collembola can high-jump 50 to 100 times the length of their body. Unfortunately for them, they have no control over this movement and can land just about anywhere, and often come down in the same spot. Unlike insects, most Collembola have no trachea (respiratory organ) or Malpighian tubes (excretory organs).
Biology and behaviour
Collembola are ametobolous insects, i.e. the individual that emerges from the egg is similar to the adult, but smaller, and with no mature reproductive system. Collembola can moult four or five times before attaining sexual maturity. Once they reach the adult stage, they will continue to moult periodically, unlike most insects. Each moult is preceded by a period of intense fasting so that the old tegument can be shed more easily. Reproduction in this group is variable. Some species perform elaborate sexual displays; others reproduce by parthenogenesis (female clones). But the males generally produce a spermatophore (an envelope containing the spermatozoons) that the female introduces into her genital tract. When the eggs are laid, the females sometimes coat them with a sticky substance to protect them against environmental conditions and predators. Collembola have a very short life cycle and can reach sexual maturity in less than three weeks.
Places where they can be found
Collembola are present in almost all habitats, except in the middle of lakes and oceans. They can be found in forest and farm soil, under moss, leaf beds, bark and stones, the tops of trees, in plants, on volcanoes and glaciers, in caves, etc. Some species live in salt water, others in fresh water. They are at home in places with high humidity and where organic materials are plentiful. They can reach a density of as many as 100,000 individuals per square meter, and up to 10 million per cubic meter. Collembola can also be found in dwellings. They prefer humid places such as basements, kitchens and bathrooms, as well as recent constructions where the wood, plaster and concrete are still moist. They can also be found in indoor plant soil. Despite their great numbers, Quebec’s Collembolan do not usually cause any damage and are harmless to humans, plants and other animals. However, the species Bourletellia hortensis is known for ravaging strawberry and raspberry plants. Spreading an insecticide on the plants usually solves the problem.
Collembola have a very significant ecological role to play since it is they who break down organic materials, transport fungus spores, and ensure microbial balance. Apart from their ecological role, they also represent a food source for various animals such as ants, beetles, lizards, frogs, small fish, etc. They feed mainly on fungus, spores, decomposing plant or animal materials, bacteria, plants, and small invertebrates.
In light of their significant ecological role, Collembolan populations should never be controlled in their natural environment. On the other hand, when they are present in dwellings, it’s a different matter entirely. One simple and effective control method is to dry out rooms that are excessively humid. Repairing water leaks and installing a dehumidifier or fan should suffice. You should also eliminate bathroom mould and get rid of any other moist or mouldy objects. Minimizing the use of mulch around house foundations is also recommended.
Other interesting facts
Collembola have very primitive characteristics and have apparently been around since the Devonian period some 400 million years ago. Individuals from that era are identical to those of today. Because of their morphological traits, taxonomists no longer consider them insects. The current classification dissociates Entognatha (Collembola, Protura, Diplura) from Insects. Some taxonomists consider them closer to crustaceans than insects.
Collembola species that live in dry environments are physically adapted to their habitats and often have bodies covered with scales or silk to help reduce water loss.
Another interesting fact is that Collembola are often used as a main diet to feed animals living in a terrarium (frogs, lizards, etc.). Because of their small size and high nutritional value, they are an ideal foodstuff and are much more nourishing than Drosophila.