Idiosoma nigrum
Encyclopedia
Idiosoma nigrum, also called Black rugose trapdoor spider, occurs only in south-western Australia, in dry woodlands east of the Darling Scarp
and north to Moore River
.
Females can reach a length of about 30mm, males about 18mm.
I. nigrum digs burrows up to 32 cm deep.
habitats. They live in burrows
up to 32 cm deep. These spiders construct an arrangement of leaves
and twig
s radiating out from the burrow entrance to serve as remote sensing
device - any movement alerts the spider to the presence of prey. Rather than foraging
only at the burrow mouth (as many other trapdoor spider
s do), these spiders charge out to grab animals on the trip-lines - especially ant
s, but also beetle
s, cockroach
es, millipede
s and moth
s. This twig-line feeding strategy increases the spider's foraging area and its chances of catching food.
The rugose spider has a thickened cuticle
which serves as an effective armour
. A few centimeters below its thin, wafer-like door, the vertical burrow narrows abruptly. When threatened by a predators the spider drops head-down into this narrowed section, phragmotically plugging it with the shield-like abdomen. Confronted by this, predators like scorpion
s, centipede
s, hunting wasps and even bird
s, often give up and go away. However, this defense has been breached by certain parasitic wasp
s that can manoeuvre their paper-thin abdomens and long, slender egg-laying tubes (ovipositor
s) down along the grooves on the spider's abdomen, allowing their eggs to be laid on the softer cuticle at the front of the abdomen. The wasp larva
that emerges is difficult for the spider to dislodge from that area and it can safely start devouring its victim alive.
The thick cuticle also prevent against water loss through evaporation.
During autumn, the smaller, long-legged male spiders (up to 18 mm body length) look for females. Mating takes place in the female's burrow. Eggs are laid during late spring and early summer and the young emerge from the egg sac in mid-summer. They remain in the mother's burrow until early winter, when rainstorms moisten and soften the ground. This ensures that the young dispersing on the ground are not going to suffer excessive water loss and will be able to dig their burrows.
Darling Scarp
The Darling Scarp, also referred to as the Darling Range or Darling Ranges, is a low escarpment running north-south to the east of the Swan Coastal Plain and Perth, Western Australia...
and north to Moore River
Moore River (Western Australia)
Moore River is a river in the Wheatbelt of Western Australia.The headwaters of the river near Walebing and flow westerly before joining with the Moore river East near Mogumber then flow in a Westerly direction...
.
Females can reach a length of about 30mm, males about 18mm.
I. nigrum digs burrows up to 32 cm deep.
Biology
The Black Rugose Trapdoor Spider is adapted for life in semi-aridSemi-arid
A semi-arid climate or steppe climate describes climatic regions that receive precipitation below potential evapotranspiration, but not extremely...
habitats. They live in burrows
Burrows
Burrows is a provincial electoral division in the Canadian province of Manitoba. It was created by redistribution in 1957, and formally came into existence in the provincial election of 1958. The riding is located in the northern part of Winnipeg....
up to 32 cm deep. These spiders construct an arrangement of leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
and twig
Twig
A twig is a small thin terminal branch of a woody plant. Twigs are critically important in identification of trees, shrubs and vines, especially in wintertime. The buds on the twig are an important diagnostic characteristic, as are the abscission scars where the leaves have fallen away...
s radiating out from the burrow entrance to serve as remote sensing
Remote sensing
Remote sensing is the acquisition of information about an object or phenomenon, without making physical contact with the object. In modern usage, the term generally refers to the use of aerial sensor technologies to detect and classify objects on Earth by means of propagated signals Remote sensing...
device - any movement alerts the spider to the presence of prey. Rather than foraging
Foraging
- Definitions and significance of foraging behavior :Foraging is the act of searching for and exploiting food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce...
only at the burrow mouth (as many other trapdoor spider
Trapdoor spider
Trapdoor spiders are medium-sized mygalomorph spiders that construct burrows with a cork-like trapdoor made of soil, vegetation and silk. Some similar species are also called trapdoor spiders, such as the Liphistiidae, Barychelidae, Cyrtaucheniidae and some Idiopidae and Nemesiidae...
s do), these spiders charge out to grab animals on the trip-lines - especially ant
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
s, but also beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s, cockroach
Cockroach
Cockroaches are insects of the order Blattaria or Blattodea, of which about 30 species out of 4,500 total are associated with human habitations...
es, millipede
Millipede
Millipedes are arthropods that have two pairs of legs per segment . Each segment that has two pairs of legs is a result of two single segments fused together as one...
s and moth
Moth
A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth , with thousands of species yet to be described...
s. This twig-line feeding strategy increases the spider's foraging area and its chances of catching food.
The rugose spider has a thickened cuticle
Cuticle
A cuticle , or cuticula, is a term used for any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticles" are non-homologous; differing in their origin, structure, function, and chemical composition...
which serves as an effective armour
Armour
Armour or armor is protective covering used to prevent damage from being inflicted to an object, individual or a vehicle through use of direct contact weapons or projectiles, usually during combat, or from damage caused by a potentially dangerous environment or action...
. A few centimeters below its thin, wafer-like door, the vertical burrow narrows abruptly. When threatened by a predators the spider drops head-down into this narrowed section, phragmotically plugging it with the shield-like abdomen. Confronted by this, predators like scorpion
Scorpion
Scorpions are predatory arthropod animals of the order Scorpiones within the class Arachnida. They have eight legs and are easily recognized by the pair of grasping claws and the narrow, segmented tail, often carried in a characteristic forward curve over the back, ending with a venomous stinger...
s, centipede
Centipede
Centipedes are arthropods belonging to the class Chilopoda of the subphylum Myriapoda. They are elongated metameric animals with one pair of legs per body segment. Despite the name, centipedes can have a varying number of legs from under 20 to over 300. Centipedes have an odd number of pairs of...
s, hunting wasps and even bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s, often give up and go away. However, this defense has been breached by certain parasitic wasp
Wasp
The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...
s that can manoeuvre their paper-thin abdomens and long, slender egg-laying tubes (ovipositor
Ovipositor
The ovipositor is an organ used by some animals for oviposition, i.e., the laying of eggs. It consists of a maximum of three pairs of appendages formed to transmit the egg, to prepare a place for it, and to place it properly...
s) down along the grooves on the spider's abdomen, allowing their eggs to be laid on the softer cuticle at the front of the abdomen. The wasp larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
that emerges is difficult for the spider to dislodge from that area and it can safely start devouring its victim alive.
The thick cuticle also prevent against water loss through evaporation.
During autumn, the smaller, long-legged male spiders (up to 18 mm body length) look for females. Mating takes place in the female's burrow. Eggs are laid during late spring and early summer and the young emerge from the egg sac in mid-summer. They remain in the mother's burrow until early winter, when rainstorms moisten and soften the ground. This ensures that the young dispersing on the ground are not going to suffer excessive water loss and will be able to dig their burrows.
External links
- More information and pictures
- The World Spider Catalog, V8.0 Idiopidae