[填空题]All the silk produced by spiders construct webs to catch their food,

[填空题]All the silk produced by spiders construct webs to catch their food,

[单项选择]Some spiders hunt on the ground, others build webs to trap their food, but the grass water spider catches its prey by running along the surface of the water.
This special water spider lives on the grassy banks of streams where mosquitoes, damsel flies and other insects come to feed and breed.
Although it is one of the largest spiders in New Zealand, it has an unusual ability. It doesn’t disturb the water as it waits for its meal, and there is barely a ripple when it skims across the surface at lightning speed to catch its prey.
Grass water spiders deal swiftly with larger insects like damsel flies by pulling their heads under the water and holding them there until they drown.
After a meal, the grass water spider spends up to half an hour grooming itself. It wipes its eight eyes, brushes its antennae, and takes special care to clean the hairs on its body.
It is the hairs that trap tiny bubbles of air so that the spider can run down a blade of grass and stay unde
A. In a web
B. By drowning
C. By poisoning
D. With its antennae

[填空题]Not all the poison glands possessed by spiders are dangerous to human beings.

[填空题]

Spiders

Spiders can be distinguished from other arachnids because the prosoma (combined head and thorax) is only separated from the opisthosoma (abdomen) by a narrow waist, in other arachnids the whole body appears to be much more of a single unit. All spiders produce silk, but only some construct webs to catch their homes and to protect their eggs.
All spiders possess poison glands but very few of them are dangerous to humans, of the 600 species in Britain only 12 (at least one of these is a recent human assisted colonist) are strong enough to pierce the human skin, and apart from allergies, none are more dangerous than a common wasp. Most spiders have 8 eyes (though some have 6,4,2 or 0), as well as 8 legs. (By the way if you count the claws as separate leg section( which you shouldn’t really)then their legs have 8 parts as well( coxa, trochanter, femur, patella, tibia, tarsus, metatarsus, claws). There are more than 32 000 kno