Rearing the large orb-weaver spider, Argiope lobata

Guy Tansley

Collecting
Egg sacs were collected whilst on holiday in Southern mainland Greece. Small isolated colonies can be found throughout the Mediterranean region, moving south as far as Southern Africa where the species is relatively common inhabiting suburban gardens. The adults were found along the quieter roadsides in Greece usually building their large webs in tall grass or low base vegetation. The surrounding area was a mixture of maquis and garrigue.

Description
A mature female measures up to 70 mm with the male being much smaller. In their natural environment where they receive prolonged amounts of direct sunlight they are vividly marked. The legs are pale yellow to white banded with black; the carapace is covered with silky silvery grey hairs; the large, lobed abdomen has a distinctive colour pattern of silver, yellow and black and the underside is circled with a star-like pattern of black and yellow.

Web Construction
Even spiderlings of A. lobata build large orb-webs - the first are approx. 50 - 100 mm in diameter and crossed with the usual zigzag stabilimentum which is a typical feature of the Argiopinae web. This diameter increases until the mature web may measure in excess of 600 mm but for some reason the stabilimentum becomes less obvious in captive specimens. There are many theories as to the use d the stabilimentum such as parasols (for thermoregulation); as an aid to collect water from early morning dew or as web strengtheners but they are most often considered to be used as anti-predator devices. This may explain why the captive specimens don't use stabilimenta in their webs built in a 'safe' environment. Once the web is built, the spider always assumes a characteristic position in the centre with the legs stretched along the lines of the stabilimentum known as the 'aligned posture'. The Argiope orb-web is extremely efficient in catching prey and as with all orb-web spiders, has amazing agility within it. The catching threads are very strong and capable of holding large prey with ease. This was demonstrated while a Greece when an adult female was observed wrapping a large cicada (Tibicen plebejus), an insect over twice the size of the spider. Spiderling webs are just as effective and will successfully secure second instar crickets. Web construction usually takes place under the cover of darkness and this is performed at a very slow and graceful pace which is an amazing sight if observed under a red light. If prey related damage is slight, then the spider will simply do running repairs to the web but complete re-spinning only occurs either after web destruction or when the web sight is unfavourable (e.g. due to disturbance or lack prey etc).

Food and Water Requirements
A. lobata will take a wide variety of prey which can be easily dropped into the web. Appropriate sized insects should be used relating to the size of the spider, i.e. spiderlings will accept fruit flies, micro crickets and hatchling mealworms; adults can be fed anything as large as adult crickets, locusts and large moths. When the prey is caught, the spider will first locate it by tugging on the web then quickly approach it, wrap it up by drawing out wide sheets of silk with the rear legs and finally bite. Once subdued the prey is cut free and hauled back up to the centre where it is consumed while the spider resumes it's position in the hub. Eventually the food is reduced to a small ball of indigestible matter and discarded. If further insects become caught in the web while the spider is feeding, these will also be taken, wrapped and subdued but will be left slung in the web for future consumption. If, however, the spider refuses food due to being well fed, has entered apolysis (pre-moult) or the prey is too large, it will react in a number of ways. Often it will try to escape from the web via one of the many construction lines or simply let go of the web altogether and drop to a safe distance on a 'life line' of silk, only returning to the hub sometime after the disturbance is over. Another method of defence is by the rapid vibration of the web as it sits in the centre. This enables the spider to shake free any unwanted prey and also may be used to deter flying predators such as birds - vibrating in this manner reduces the spider to a blur making it impossible for it to be picked from the web. Water can be provided approx. twice a week after feeding and increased during times of moulting. This can be done using a house plant spray, lightly misting the web with tepid water. The spider will eagerly drink from the web or surrounding vegetation as well as collecting the small drops from its abdomen and legs.

Housing
When the spiderlings begin to disperse from the egg sac, any large, tall container can be used to house them. Large sweet jars or food storage containers are ideal and this should be covered with a piece of fine netting to allow any excess moisture to evaporate as the small spiders can easily become trapped in the tiny droplets of condensation and drown. The spiderlings can be kept communally at any size or stage providing there is enough room for them to build their webs. The container should be furnished with a few firmly fixed twigs to aid web construction although no substrate is needed. As they grow they can either be moved into separate containers or into specially built wooden 'orb-frames'. These frames provide an ideal space saving alternative as well as an excellent means of display. They should be at least 24" square and for the best results, a piece of black nylon netting should be stretched across the front and back for viewing. A hole can be drilled at either end to give access when feeding, watering and cleaning.

Moulting
The female requires approx.  5 - 6 moults to reach sexual maturity while the male matures in only 4. Ecdysis always occurs in the hub of the web where the spider spends most of its life. Predicting a moult is more difficult than with tarantulas as no darkening is noticeable during apolysis. Definite signs of an approaching moult are lack of appetite three to four days from moulting and the spider will spin a mesh of threads slightly behind the main web centre. This mesh acts as the spiders only means of defence when moulting and guards it against predators during this vulnerable time. Moulting occurs under the cover and safety of darkness and only takes 10 to 15 minutes. Once complete, the exuvium (cast skin) is discarded from the web and drying out time is brief, feeding resuming as early as within the following 48 hours. Spraying with water should be increased when the silk protection mesh is noticed to aid successful ecdysis and following moulting the spider will be extremely thirsty so water should be provided using a plant spray.

Sex Determination
If several specimens are being kept, sex determination is a simple affair. Immature males are easily distinguished at a very early stage as their large bulbous palps are noticeable after their second moult. The males' abdomen never achieves the unusual shape or vivid colour of the female and he is, in comparison, much smaller with a leg span of approx. 14 mm, in relation to the females 45 mm span. If successful breeding is to be achieved the males growth must be slowed down in order to coincide with the maturing of the female and simply reducing the temperature of its surroundings and decreasing the amount of food given can do this.

Breeding
Once the female is mature she should be allowed to feed up for a few weeks before mating and the same goes for the mature male although he will probably only take one or two items before beginning to wander in search of a mate. When the male is introduced into the females' container, he will almost certainly be eager to mate. First he will spend some time on the outskirts of the web, testing it with his forelegs and vibrating his body occasionally. Moving further towards the centre he then cuts a hole near the hub and secures his mating line. Sitting on this line he begins to pluck out his courtship message and eventually persuades the female to climb onto his mating thread. If she is willing to mate, she will follow him onto the line and the male approaches slowly until he touches her with his first pair of legs, vibrating his body continuously. When close enough, he jumps towards her and she responds by quickly grabbing him and pulling him close to her sternum with the tips of her legs. The male then inserts his palps very briefly and if he's lucky, jumps free of the females grasp whom by this time has decided that he'd probably make a better meal than a mate! The male usually escapes after the first couple of pairings except for the loss of a leg or two but old or severely handicapped males tend to fall victim to the female. Another method of pairing A. lobata is possible which reduces the risk to the male and this involves predicting the time of the females maturing moult. If this can he successfully determined, the male should be introduced approx. 24 hours preceding the moult and he will sense that she's not mature and simply wait near her until she moults. As she begins to moult, the male moves in and mates with the vulnerable female who is in no position to do him any harm.

Egg sac construction and incubation
The females appetite will be ferocious after mating, tackling almost anything, which falls into her web; adult crickets, locusts and even large moths will be eagerly taken. Soon, depending on the conditions of warmth etc., the egg sac will be laid. If the spider is housed in an 'orb frame', the sac will be constructed on the outskirts of the web near one of the top corners. Construction takes place at night and is a lengthy affair, the final product being a cup-like structure made up of several types of silk. Inside the egg case is filled with wool-like silk to give the eggs maximum protection and the outer covering is made up of tough, waterproof silk. The top is finally covered with more wool-like silk. In the natural environment the egg sac would be attached to nearby vegetation but in captivity, the sac is suspended from a mesh of several construction threads. A female will produce up to three egg cases, each one becoming progressively smaller and they will all be built close to each other in the same corner. In the wild the eggs spend the winter months within the sac and emerge as the weather becomes warmer but incubation times in captivity can he reduced easily to as little as four months. The eggs should be left with female (or until after she has died) then they should be removed and stored at a lower temperature for the following four weeks. After this simulated 'winter' period, simply place the egg sac in a large ventilated box returning it to the warmer conditions and after one to two weeks later, the spiderlings will begin to hatch. They should be sprayed regularly upon emerging and after a further week or so, they will moult and can be separated.

Longevity
A. lobata females can live up to 13 months in captivity but the males die soon after maturing. Infertile egg cases will be laid by unmated females, but for some unknown reason, the spider tends to drop all the eggs onto the floor of the cage, something which doesn't happen when the eggs are fertile.

This article first appeared in the Journal of the British Tarantula Society, 10 (1): 9-16 (1994).