In the article "Elements of taxonomy" we note, within the animal kingdom, a phylum called Arthropods (from the Greek arthron (articulations) and podos (feet). These invertebrates themselves have four sub-branches in which Crustaceans, Arachnids, Hexapods (hexa "six", podos "feet") and Myriapods are classified. It therefore seems natural to carry out a summary review of these "neighbors" living in the same biotopes, of which I will mention only a few of the best known representatives.
The order of the Isopods is a sub-branching Crustacean (50 000 species) which, a priori, makes us think shrimp or lobster ... But here it is question of terrestrial crustaceans, to be simple, woodlice which count 3000 known species . Inoffensive for springtails, they are like the latter detritiphages. Their diet comes from decaying plant matter. Equipped with seven pairs of legs, they can escape in case of danger or curl up to protect themselves under their exoskeleton made up of articulated and rigid segments. They live up to four years and perform regular moults (monthly). Lucifuges, they look for dark and humid places where they often evolve in colonies. They are used as bioindicators in soil quality studies. See images: Crustaceans.
In this class, we find the formidable predators of springtails that are spiders (47,000 species known in the world, including about 1700 listed in France), pseudo-scorpions and mites, all with four pairs of legs and chelicera.
Their chelicerae (from the Greek khêlê (tongs) and kêras (horn) are powerful tongs capable of penetrating the exoskeleton of their prey. Equipped with sharp hooks they can inoculate their venom via two channels ending at their ends. As a general rule, predators of springtails are not spiders weaving a web but those who roam the ground in search of prey, such as Lycosidae, Linyphidae or Salticidae (below right: a Heliophanus cupreus has just caught an Orchesella villosa). View images (sorted by family): Spiders.
They count around 3800 known species in the world, for about 120 identified in France. They look like scorpions although their size is much smaller (2 to 4 mm on average). Sometimes we find them clinging to other insects they use as a means of movement. They hunt while strolling in the litter or under the bark of old trunks, putting forward the pincers they carry at the ends of their pedipalpes. They have no tail end with a venomous sting, but their claws have venom glands that they use to paralyze or kill their prey. Some pseudo-scorpions also have silk-producing glands that they can use to immobilize their catch. See images: Pseudoscorpions.
Their bodies are not divided into distinct sections like spiders or pseudoscorpions. Those who evolve in litter are very small (0.2 to 1 mm on average). They move frequently by attaching themselves to other animals that they can also parasitize. These are the most common arachnids in the soil but, despite nearly 50 000 listed species, they are hardly distinguished because of their size and habitat. Like springtails they are able to survive in environments subject to extreme conditions. Some of them feed on dead material or excrement while others, such as Gamases or Actinedidae are carnivorous and hunt the microfauna. See images: mites.
They are distinguished from spiders by their eight generally longer and filiform legs, an undissociated thorax of the abdomen, a single pair of eyes and the absence of glands capable of secreting silk. There are 130 known species in France for around 6,500 listed worldwide. Although possessing chelicera, they have no venom. Rather omnivorous, they can also hunt small insects, other arachnids or springtails. See images: Opiliones 1- Opiliones 2- Opiliones 3.
Coming from the association of two Greek words, murios "ten thousand" and podos "foot", they are commonly called centipedes. Their body is formed by a prolonged head of a large number of rings (may be around 200) which each carry one or two pairs of legs. The succession of these rings of similar aspects makes it possible to distinguish neither thorax nor abdomen. Within the sub-phylum Myriapodes, which has more than 5000 known species to date, the class of Chilopods carrying a pair of legs by segment is represented, among others, by the centipede (below left), carnivores with venomous glands and whose flattened body has "only" 21 pairs of legs. In this same class are also the Geophilomorphs (below, in the middle) more elongated and also predators capable of producing toxic compounds. Another class is the Diplopoda (below right), which has a large number of segments bearing two pairs of legs and whose body is cylindrical. The latter unlike the previous ones are vegetarian and therefore harmless for springtails. They are often seen rolling in a ball in case of danger. See images: Myriapodes.
Represented by Japygidae (below left) 1 and Campodea (right), they form a class of small animals living in moist soils. As springtails feed on plant waste, their diet is still relatively unknown and scientists admit a probability of predation towards other invertebrates. In case of danger, they fled. Lumifuges, they spend their life underground, which explains their depigmentation. They have two antennas, have no eyes and are entognaths. Their thorax supporting three pairs of legs is well dissociated from the abdomen and ends with two circles that can have sensory functions or be used as a defense. See images: Diploures.
Within this order are bees, wasps and ants. It is precisely these that I retain because they evolve on the ground, near springtails, some of their species do not disdain as prey. On the other hand, we can note a rather surprising example of cohabitation in perfect harmony. This is the case for entomobryomorphic springtail of the species Cyphoderus albinus found only in the vicinity of anthills. The latter play the role of cleaning agents and even carry the pheromones of the ant communities where they live; the latter consider them to be theirs. See images: Hymenoptera.
The litter contains a large number of beetles in the larval or adult state which would be too laborious to list the families. Although many of them are carnivores like for example (below left to right) the larva of Pyrochroa (cardinal), Ampedus preatus, Tachyporus (staphylinidae) or Carabidae as Carabeus violaceus, they rub shoulders springtails without causing them too much damage because they are not part of their preferred food targets. See images: Coleoptera.
They are usually only found in litter when larvae are present. Larvae do not present a risk for springtails with which they cohabit generally underground or in the wettest areas. They feed on plants and pose a danger only for certain plants from which they eat root hairs, which prevents them from feeding properly and leads to their withering away. See images: Diptera.
Archeognathes and Zygentomes:
They form two distinct orders that have replaced that of the Thysanura. Several families represent them, of which I will mention only Machilidae (Machilis) and Lepismatidae (Lepismus) which evolve near the litter, although they are also found in the houses where they can be invasive. Characterized by their external mouthparts, their body is covered with scales. The Machilis (below left) jump by contracting the thorax-abdomen. The silverfish (below right) do not jump but move very fast. Both feed on plant debris or dead animals and favor hot, humid places. They are safe for springtails.
These are the largest group after insects, with some 40,000 living species listed. Most of the population evolves in the oceans, only a very small part of them evolve on the Earth. They are fond of the wettest sites, although most terrestrial species can be protected from dehydration by secreting a protective cap. Except for very rare species that can be carnivorous, their food and mainly of vegetable origin. Their cohabitation with springtails poses no problem. Below from left to right: Oxychilus, Helicodonta obvoluta, Macrogasta ventricosa. See images: Gastropods.
After this brief overview, it would be illusory to want to review all the families of invertebrates that evolve in the vicinity of springtails. In addition to those I have just mentioned, it would indeed be necessary to reckon with the protozoa, rotifers, nematodes, earthworms already mentioned in the article on organic decomposition.
1 Photo of Japygidae: © Simon Oliver, (source flickr)
Other Illustrations: © Philippe Garcelon.