Stegodyphus lineatus
Encyclopedia
Stegodyphus lineatus is the only Europe
an species of the spider
genus Stegodyphus
.
is whitish with two broad black longitudinal stripes. Males and females look similar, but the male is generally richer in contrast and has a bulbous forehead. The species name refers to the black lines on the back of these spiders (not present in all individuals).
between twigs, mostly of low thorny shrubs. The web has a diameter of about 30 cm and is attached to a retreat made out of silk and covered with debris and food remains. Retreat is a cone-shaped structure about 5 cm long, which has an entrance at one end. The spiderlings hatch in this retreat, being released from their cocoon by their mother and then protected by her for a further two weeks. Adult males can be found in spring.
Offspring are matriphagous meaning they eat their own mother. Females can mate with several males (polyandry). While females may gain some benefits from multiple mating
s , overall polyandry is costly and mated females are often aggressive towards males (also see below). Males may chance upon only one or two mates in their entire lifetime. Egg sacs are lost quite frequently due to predation by ants and females are able to lay another clutch if they lose their first. This represents an opportunity for males, however, who can secure themselves a mate by simply disposing of her offspring (this can occur because some males are still seeking mates when most females have already laid). Males go about this by detaching the egg sac with their chelicerae
, moving it to the entrance, then simply tossing it to the ground.
This behaviour, known as infanticide
, is not so straightforward for males however. Female fitness
is greatly reduced by the loss of their young, with the female being less likely to survive until her next lot of offspring can hatch, as well as having fewer eggs the second time. Their offspring also hatch later in the season and are less likely to thrive themselves. With this in mind, it comes with little surprise that females aggressively attend to their nest, chasing off around half the males that come nearby. Males can sustain injuries in these battles with the larger females, and in some cases the female not only kills, but eats
the male intruder. For males however there is little option but to take this risk, resulting in sexual conflict that sees around 8% of egg sacs destroyed.
, southern Greece
including Crete
) and stretches up to Tajikistan
.
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
an species of the spider
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
genus Stegodyphus
Stegodyphus
Stegodyphus is a genus of araneomorph spiders in the family Eresidae. The 21 species are distributed from Africa to Europe and Asia, with two species Stegodyphus is a genus of araneomorph spiders in the family Eresidae. The 21 species are distributed from Africa to Europe and Asia, with two species...
.
Description
Males are up to 12 mm long, females up to 15 mm. The colour can range from whitish to almost black. In most individuals the opisthosomaOpisthosoma
The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma . It is a distinctive feature of the subphylum Chelicerata...
is whitish with two broad black longitudinal stripes. Males and females look similar, but the male is generally richer in contrast and has a bulbous forehead. The species name refers to the black lines on the back of these spiders (not present in all individuals).
Behaviour
These spiders build a webSpider web
A spider web, spiderweb, spider's web or cobweb is a device built by a spider out of proteinaceous spider silk extruded from its spinnerets....
between twigs, mostly of low thorny shrubs. The web has a diameter of about 30 cm and is attached to a retreat made out of silk and covered with debris and food remains. Retreat is a cone-shaped structure about 5 cm long, which has an entrance at one end. The spiderlings hatch in this retreat, being released from their cocoon by their mother and then protected by her for a further two weeks. Adult males can be found in spring.
Offspring are matriphagous meaning they eat their own mother. Females can mate with several males (polyandry). While females may gain some benefits from multiple mating
Mating
In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...
s , overall polyandry is costly and mated females are often aggressive towards males (also see below). Males may chance upon only one or two mates in their entire lifetime. Egg sacs are lost quite frequently due to predation by ants and females are able to lay another clutch if they lose their first. This represents an opportunity for males, however, who can secure themselves a mate by simply disposing of her offspring (this can occur because some males are still seeking mates when most females have already laid). Males go about this by detaching the egg sac with their chelicerae
Chelicerae
The chelicerae are mouthparts of the Chelicerata, an arthropod subphylum that includes arachnids, Merostomata , and Pycnogonida . Chelicerae are pointed appendages which are used to grasp food, and are found in place of the chewing mandibles most other arthropods have...
, moving it to the entrance, then simply tossing it to the ground.
This behaviour, known as infanticide
Infanticide (zoology)
In animals, infanticide involves the killing of young offspring by a mature animal of its own species, and is studied in zoology, specifically in the field of ethology. Ovicide is the analogous destruction of eggs. Although human infanticide has been widely studied, the practice has been observed...
, is not so straightforward for males however. Female fitness
Fitness (biology)
Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...
is greatly reduced by the loss of their young, with the female being less likely to survive until her next lot of offspring can hatch, as well as having fewer eggs the second time. Their offspring also hatch later in the season and are less likely to thrive themselves. With this in mind, it comes with little surprise that females aggressively attend to their nest, chasing off around half the males that come nearby. Males can sustain injuries in these battles with the larger females, and in some cases the female not only kills, but eats
Cannibalism (zoology)
In zoology, cannibalism is the act of one individual of a species consuming all or part of another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded for more than 1500 species...
the male intruder. For males however there is little option but to take this risk, resulting in sexual conflict that sees around 8% of egg sacs destroyed.
Distribution
S. lineatus occurs in Europe only in the southern Mediterranean region (south of BarcelonaBarcelona
Barcelona is the second largest city in Spain after Madrid, and the capital of Catalonia, with a population of 1,621,537 within its administrative limits on a land area of...
, southern Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
including Crete
Crete
Crete is the largest and most populous of the Greek islands, the fifth largest island in the Mediterranean Sea, and one of the thirteen administrative regions of Greece. It forms a significant part of the economy and cultural heritage of Greece while retaining its own local cultural traits...
) and stretches up to Tajikistan
Tajikistan
Tajikistan , officially the Republic of Tajikistan , is a mountainous landlocked country in Central Asia. Afghanistan borders it to the south, Uzbekistan to the west, Kyrgyzstan to the north, and China to the east....
.