Monday, December 24, 2012

Button/Widow Spiders - Family Theridiidae


-          - Black Button/Widow Spider: (Family Theridiidae - Latrodectus indistinctus/renivulvatus/cinctus/karooensis) Almost every major region of Africa has at least one of these species present, with the greatest density occurring in Southern Africa.  Black Button Spiders can inject strong neurotoxic venom, potentially causing heart palpitations, severe anxiety, chest pains and difficulty breathing.  However, these spiders are shy, retreating, and not aggressive. They are bound to their webs and will most often go out of their way to AVOID humans.  They also have a habit of wrapping their prey in silk before injecting venom, further reducing the chances of receiving a bite.  Victims should be kept calm and reassured that they will be fine.  However, medical attention should be sought as soon as possible, and antivenin should only be administered after observing real symptoms by a qualified medical professional.
African Black Button Spiders are generally almost completely black with some variation of a red marking on the dorsal (top) side of the abdomen.  This differs from some North American Species which are known for their red hour-glass markings on the ventral (under) side of the abdomen.  Black Buttons create messy looking space-webs, and often have several smooth round white egg casings in a retreat to one side of the web.
Similar specie: False Button Spiders (also Theridiidae, genus Steatoda) can easily be confused for a Black Button, except for the lack of any red markings on the abdomen.  Some have whitish/creamy markings on the abdomen.  Although, the venom from Steatoda is not nearly as toxic as that from Latrodectus, it can still produce a fair amount of pain and dizziness.
Steatoda sp. - FALSE BUTTON SPIDER (female): Notice the lack of any red markings on the top of the abdomen.  
Steatoda sp. - FALSE BUTTON SPIDER (female): Notice the lack of any red markings on the top of the abdomen.  
Brown Button Spider: (Family Theridiidae - Latrodectus geometricus): L. geometricus is one of the most widely spread spiders in the world, and occurs across every continent (other than Antarctica). The venom from Brown Button Spiders (also neurotoxic) is generally considered to be only 1/4th as virulent as that of the Black Buttons.  Symptoms of a Brown Button bite would be similar to those of a Black Button, but to a much lesser extent.
Brown Buttons vary from black to light brown with various markings on the top of the abdomen and a distinct red hourglass marking on the ventral side of the abdomen.  Their webs are similar to those of Black Buttons, but their round egg sacs are covered in spikes, rather than being smooth.
Latrodectus geometricus - Brown Button Spider: Very distinct red "hourglass" marking showing under the abdomen.  The often hang upside down in their webs, making this marking very visible.
Latrodectus geometricus - Brown Button Spider:  Hourglass marking just visible here.  Notice the variation in colouration on the top of the abdomen.  They can range from jet black, to brown, to striped or spotted, but the hourglass is always present.
Latrodectus geometricus - Brown Button Spider:  With Solifuge prey.
Not all member of this family are dangerous.  Dew Drop Spiders (Argyrodes spp), mentioned in the post about Kleptoparisitism are also members of this family.
House Button Spiders are also members ore Theridiidae, but are similarly harmless to humans

Sunday, December 23, 2012

What Is A Spider?


What is a spider?
The Order Araneae (Spiders) is the largest order within Arachnida, and spiders are found in every part of the world, except Antarctica.  Although many people think of spiders as being insects or “bugs”, they are in fact different in many ways from Insects.
Spiders
Insects
2 body parts (cephalothorax & abdomen)
3 body parts (head, thorax, abdomen)
4 pairs of legs
3 pairs of legs
2-8 simple eyes
Compound eyes
Do not have wings
Most have wings or vestigial wings
Carnivorous
Herbivorous and carnivorous
Ecdyse from spiderlings to adults
Complete and incomplete metamorphosis

Spiders have 8 jointed legs, 2 distinct body parts, 2-8 simple eyes, exoskeletons, silk glands (and spinnerets) and all but one family have venom glands.  There are approximately 79 families of spiders in Africa, representing about 72% of all the spider families in the world, and they can be split up into two groups: Araneomorphae and Mygalomorphae.
Araneomorphae:
Araneomorphs are what most people think of when they imagine a true spider.  Many Araneomorphs are conspicuous, easy to find, and build webs.  The quintessential orb-webs and cob-webs we all know are made by Araneomorphs.  However, not all Araneomorphs build webs; there are also several types of burrowing and free-living Araneomorphs.
Mygalomorphae:
Most African Mygalomorphs are large, robust ground/burrow dwelling spiders, most of which, despite their ‘scary’ appearance, are harmless to humans.  They have small venom glands and are often not aggressive.  Baboon and Trapdoor spiders and their relatives are Mygalomorphs
Araneomorphae
Mygalomorphae
More highly evolved
More primitive
1 pair of booklungs
2 pairs of booklungs
Chelicerae strike horizontally (against each other)
Chelicerae strike vertically (with each other)
Web-bound, burrowing, or free living
Most are burrowing or ground dwelling.
Araneomorph - In Web: Tetragnathidae -
Silver MarshSpider

Mygalomorph - Burrowing: Theraphosidae -
 Baboon Spider











Definition – Booklungs: Several thin plates of permeable membrane where gas exchange takes place with oxygen on one side of the plate and blood on the other.
Spider ecology:
Despite the negative image many people have of spiders, they play an important role in a functioning, healthy ecosystem.  With almost 8,000 different species from 79 different families represented in Africa, spiders inhabit every type of ecosystem and biome on the continent, and are an important food source for a diverse number of larger (and smaller) predators.  As spiders are carnivorous themselves, they are also important biological controllers of their prey species, keeping insect numbers in check. 
 - If every spider on the continent were to suddenly disappear, we would drown in a sea of insects!
Spiders are a fascinating group of organisms to study; behavioural differences and colour variations are as numerous as the species themselves.

Thursday, October 4, 2012

Spider Mating and Reproduction


In order for a male spider to mate with a female, he must first inform her of his presence and his intentions.  He would normally do this by tweaking and strumming on her web in a certain way that only a female of the same species would understand.  Once he is convinced that she is aware of him he can approach her.  Depending on the species, the male may then have to perform another dance or present the female with a “gift” in order to preoccupy her so that she does not eat him.  Others may have to use “tactile communication” – stroking the female’s legs – to get her “in the mood”.
Once the female is ready to mate, the male must first deposit his sperm on to the web or substrate.  He then picks up the sperm with his pedipalps and inserts them one by one into the female’s genital opening (epigynum).  The male and female of one species have perfect fitting reproductive organs like a lock and key, so that two different species can never copulate.
The males of several species of spider must retreat quickly once mating has taken place to avoid being eaten by the female. The most famous of these are the “widow” spiders (Latrodectus spp.), named after this behaviour.  However, the males and females of many other species cohabit amicably in the same web with no threat of cannibalism.
Araneomorph spider females can often store up eggs and sperm and fertilize them when they are ready.  Even after they moult (Ecdyse) they still keep the same set of eggs and sperm.
Mygalomorph spider females, however, replace the lining of their reproductive organs every time they moult, making them “virgins” again after each ecdysis.
Above: Latrodectus geometricus - BROWN BUTTON (WIDOW). The most famous examples of spider females eating their male partners after mating are the Widow spiders, but the males of many other species must also rush to escape the same fate.  However, not all spider species practise post-sex cannibalism!

LONG-LEGGED SAC SPIDERS - Family Miturgidae


Cheiracanthium Sac Spiders usually have a cream or straw-coloured body, with very black chelicerae and face.  The black face and chelicerae are the most indicative feature of these spiders.  They have long front legs that are often held out forward and bent. They build temporary sac-like silken retreats in leaves, folds in curtains, and in the corners of rooms.  They often venture indoors to hunt at night. 

Of all the commonly encountered spiders in East Africa, these are the ones to be the most wary of.
Cheiracanthium sac spiders are found throughout most of Sub-Saharan Africa and, as they are not web-bound, wander around looking for prey.  As such, they are encountered often, especially at night, and account for about 75% of all spider bites in Sub-Saharan Africa.  Cheiracanthium venom is cytotoxic, and therefore destroys tissue cells.  The initial bite is not painful, so often goes unnoticed until later when it becomes swollen, red, and itchy.  This develops into a boil-like sore and can cause great pain and fever that can last up to two weeks.  There is not much first aid that can be applied other than treating the symptoms like pain and fever.

Similar specie: There are other, similar looking, types of Sac Spiders from the family Clubionidae that are completely harmless and should not be confused with the Long-Legged Sac Spiders from the family Miturgidae.

LIFESTYLE: Free-running, ground-living, plant-living
HABITAT: on or under bark; in webbing, scrapes, or free-running, under stones; on bushes and plants; in and under leaf litter.
BODY SIZE (excluding legs): 3-12.5 mm
ACTIVITY: Nocturnal
DANGER: Venomous (See above)
 Above: Cheiracanthium sp.(furculatum?) - LONG LEGGED SAC SPIDER  Notice the jet black face and chelicerae (fang-bases) compared to the rest of the beige/straw-coloured body.  Notice also the very long front pair of legs held forward.
Above: Cheiracanthium sp. - LONG LEGGED SAC SPIDER.

Wednesday, October 3, 2012

KLEPTOPARASITISM - What the heck is that!?


Kleptoparasitism
Kleptoparasitism describes the behaviour of a few different genera of spiders that steal the food from other spiders.  The most obvious example one is likely to come across is the tiny Dew-Drop Spider (Argyrodes spp) feeding off the discarded prey remains of the massive Golden Orb Web Spider (Nephila spp).  Some species will even feed on the web itself for added protein. 
 Above: Argyrodes sp. (Family Theridiidae) - DEW DROP SPIDER.  These tiny spiders often live in the webs of a much larger Nephila sp. (Family Nephilidae) Golden Orb Web Spider, living off of the discarded remains of old prey.  I personally watched this particular individual actively steal fresh prey from the larger spider when the larger spider was distracted (another fly was caught in the web elsewhere).
Dew Drop Spiders come in all sorts of funny shapes, with large bulbous abdomens, as shown here, or long protruding ones.
 Above: Nephila fenestrata - BLACK LEGGED NEPHILA (Golden Orb Web Spider), whose massive web harboured at least 3 Kleptoparasitic Dew Drop Spiders.


FUNNEL WEB SPIDERS – Family Agelenidae


These spiders live permanently in sheet webs built close to the substrate, with a funnel retreat at the end.  They resemble Wolf Spiders in shape and size, but their eye pattern is very different.  They have 2 large forward facing eyes surrounded in a circle by 6 more small eyes.
The sheet webs of the Grass Funnel Web Spiders (Olorunia spp.) are also very similar to the sheet webs of the Hippasa spp. Wolf Spiders.

IMPORTANT NOTE: Despite the similarity in the name to Australian Funnel Web Spiders - which are known to possess very virulent venom - African Funnel Web Spiders are HARMLESS to humans.

LIFESTYLE: Sedentary and web-bound
HABITAT: low base vegetation and grass
BODY SIZE (excluding legs): 8-12 mm
ACTIVITY: Diurnal and Nocturnal
DANGER: Harmless

Above: Tegenaria sp. - HOUSE FUNNEL WEB SPIDER. (Click on the image for a larger version to see more detail)

Tuesday, October 2, 2012

Spider Identification

The most accurate way to determine a spider’s species is to look at it under a microscope and examine the male and female reproductive organs.  In the field, this is obviously not practical, and a field guide must rely on more obvious features that can help with identification down to at least the family, and sometimes the genus, level.  There are a few spider species, however, which are distinct enough from any others that an experienced guide can identify the exact species at a glance.
In the field, there are several factors one must consider when attempting to identify a spider: habitat, web-bound or free-living, web-type, found on the ground or vegetation or near water, general impression of shape, colour, and size, and most importantly, the eye pattern.
All spiders have 2-8 simple eyes and the pattern of their eye arrangements is usually unique from one genus to another, even within the same family.
For example, a wolf spider (Family Lycosidae) will have two large eyes on the top and to the sides of the head, another two large eyes are at the forward facing, and another four smaller eyes are forward facing in a horizontal line just below.  A baboon spider (Family Theraphosidae) however has eight small eyes all in a tight cluster on the top of its flat carapace on a little bump, or protuberance.
So, although some wolf spiders can grow almost as large as a baboon spider, and can be hairy like a baboon spider, the eye pattern is distinct enough between the two that the two families should never be confused.

See Separate posts below for Baboon Spiders and Wolf Spiders for photo illustrations of eye patterns.

The identity of a web-living spider can also be narrowed down just by looking at the type of web it lives in.  There are 4 main types of webs:
-          - Orb Webs: widely considered to be the “standard spider web”.  They are generally round-ish, with radials spreading out from a hub in the centre, all hanging from a “bridge line” between two anchor points (often on trees or branches).  Example: Golden Orb Web Spiders (Family Nephilidae)
-          - Reduced or Modified Orb Webs: variations on the orb web theme, these webs sometimes do not resemble an orb at all. Example: Tropical Tent-Web Spiders (Family Araneidae)
-          - Sheet Webs: Horizontal webs constructed in a sheet.  The silk is usually not sticky like that of an orb web.  Example: Grass Funnel-Web Spiders (Family Agelenidae)

-          - Space Webs: Complex, 3-dimensional webs that appear in a variety of different configurations and habitats.  Example: Button/Widow Spiders (Family Theridiidae)

BABOON SPIDERS - Family Theraphosidae (Mygalomorphae)


In Africa, these spiders are known as Baboon spiders because of their hairy appearance and because the colour of the pads on the tarsus resembles the colour of a baboon’s foot pad.  In other parts of the world, members from this family are commonly known as Tarantulas.  Baboon spiders are very large spiders with thick legs that do not get narrower toward the end.  They live in silk-lined burrows and emerge only at night to hunt, but never move far away from the burrow.  They can live up to 25 years if they do not fall victim to predation.
Baboon spiders can be differentiated from Wolf Spiders (Family Lycosidae) by the distinct eye pattern – 8 small eyes in a tight cluster on a protuberance at the front of the cephalothorax.
They will not go out of their way to attack humans, but would rather retreat without a fight.  In Masai Mara, there is only one species of Baboon Spider, Pterinochilus chordatus.  In Kenya as a whole, there are only 7 KNOWN species (very limited work has actually been done studying Theraphosids in Kenya, and there are very possibly more than 7).  Owing to its large fangs, it can inflict a painful bite.  The venom can cause severe pain at the bite site and a tight chest, but no major systemic effects.

LIFESTYLE: Sedentary and ground-living
HABITAT: In Burrows
BODY SIZE (excluding legs): 13-64 mm
ACTIVITY: Nocturnal
DANGER: All are harmless except for Pterinochilus murinus (found in central and South-Eastern Kenya)

 Above: Pterinochilus chordatus - BABOON SPIDER.  Common in Southern and Central Kenya.  Notice the eye pattern - very distinct from that of a Wolf Spider (Lycosidae).  Here, eight small eyes are all grouped together in a tight bunch on a raised protuberance in front of the chelicerae (fang bases).
 Above: Pterinochilus chordatus - BABOON SPIDER. Notice the width of the legs does not vary much from the base to the tip - differing from the pointed feet of a Wolf Spider (Lycosidae).  Notice also the horizontally positioned chelicerae (fang bases) compared with the very vertical chelicerae of Lycosids.
Above: Eucratoscelus sp. - BABOON SPIDER.  Found in Central, Northern, and South Eastern Kenya - this was taken in central Laikipia.  (Photo Credit: Sophie Woodrow)
Above: Eucratoscelus sp. BABOON SPIDER. Again, notice the distinct eye pattern - very different from that of a Wolf Spider (Lycosidae).  Also, a fully grown Baboon Spider will generally be much bigger than a fully grown Wolf Spider - they can be almost twice the size.

GOLDEN ORB WEB SPIDERS - Family Nephilidae


Golden Orb Web Spiders – Family Nephilidae

The members of this family are usually very large with cylindrical abdomens and a black cephalothorax.  They build huge orb webs between trees with golden coloured silk.  The exception to this is the Hermit Spider (Nephilengys cruentata), which builds only a partial orb-web with a funnel retreat in one corner where it can hide.  It is also usually slightly smaller than the typical Nephila spp.

LIFESTYLE: Sedentary and web-bound
HABITAT: in trees, between trees/bushes, low vegetation or under grass.
BODY SIZE (excluding legs): up to 35 mm
ACTIVITY: Diurnal
DANGER: Harmless
 Above: Nephila senegalensis - BANDED LEGGED NEPHILA. Large body, very long legs, yellow/red bands on front legs. This particular one was not fully grown.  The span of its web was about 2 metres.
 Above: Nephila senegalensis - BANDED LEGGED NEPHILA
 Above: Nephila fenestrata - BLACK LEGGED NEPHILA. One of the largest Nephila species.  These spiders often have tiny Dew Drop Spiders (Argyrodes sp.) from the family Theridiidae living in their web as "Kleptoparasites".  Kleptoparasites live off of the remains of prey (or stolen prey) from the host spider, and are often much smaller than the host.  The Dew Drop Spiders live on the fringes of the web and wait for opportunities to steal tiny morsels of food from the huge host.  They sometimes also eat part of the web itself for added protein.
 Above: Nephila fenestrata - BLACK LEGGED NEPHILA (underside).
 Above: Nephilengys cruentata: HERMIT SPIDER.  These beautiful spiders build only partial orb-webs which terminate in a funnel/tunnel into some crevice or hole where they can hide during the day (or when threatened).  Their web is usually not as brightly golden coloured as members of the genus Nephila.  Buildings with overhanging roofs provide a great place for these spiders to build their large webs.
Above: Nephilengys cruentata: HERMIT SPIDER.

HACKLED ORB WEB SPIDERS - Family Uloboridae


Spiders in the family Uloboridae are the only spiders in the world that do not possess venom glands.  They wrap their prey in silk and cover it in digestive enzymes.  Several genera exist, with webs ranging from perfectly horizontal orb webs (Uloborus spp) to single horizontal silk lines (Miagrammopes spp).  Uloborus spp have long front legs held forward and slightly apart and a very bulbous abdomen.  Miagrammopes hold their long front legs in a similar fashion, but have long slender abdomens, giving the spider a curious shape. 

LIFESTYLE: Sedentary and web-bound
HABITAT: On bushes and low vegetation and around the eaves of buildings
BODY SIZE (excluding legs): 3-10 mm
ACTIVITY: Nocturnal
DANGER: Harmless (more harmless than any other!)
 Above: Uloborus sp. - HACKLED ORB-WEB SPIDER. Notice four front legs held forward and then split at the front.  Lots of debris in the web is also common, as shown here.  These webs look like typical orb webs, built almost horizontally, with the spider hanging upside down on the underside of the web.  Small spiders, often found under the eaves of roofs.
Above: Uloborus sp. - HACKLED ORB WEB SPIDER. Notice the large, odd-shaped abdomen, which differs from Miagrammopes sp. (not shown here) which has a long slender abdomen.