Question

Spider web is formed by a fluid secreted by its
A. Abdominal gland
B. Salivary gland
C. Cephalothorax
D. None of the above

Answer 1

Hint: Spider web is created by the spider through its proteinaceous silk. This spider web is usually secreted from the spinneret glands of the spider which is mostly used in the catching of its prey.

Complete answer:
-Option (A) is correct. The spider web is usually formed from the spider silk that is secreted from its spinneret glands. As these glands are located at the tip of the abdomen hence, they are also known as abdominal glands. Thus, the spider web is formed by a fluid secreted by its abdominal gland.
-Option (B) is incorrect. The silk-producing glands of spiders are located at the tip of their abdomen. Hence, they are also known as abdominal glands and not salivary glands.
-Option (C) is incorrect. Cephalothorax in spiders is the region comprising the head and thorax fused, as distinct from the abdomen behind. 

This fusion is seen in groups: chelicerates and crustaceans. This region does not secrete the spider silk that forms the spider web.
-Option (D) is incorrect. As abdominal glands are also known as spinnerets glands that secrete the fluid that forms spider web, therefore option (A) is correct. Hence, the ‘none of the above’ option cannot be correct.
Hence, the correct option is (A).

Note:
Spiders secrete silk that is liquid proteins and this silk enters into the ducts before exiting the spider. In these ducts, the liquid portion of the silk protein is drawn away, which transform it into solid fiber as it is pulled through the spider’s acidic silk glands or spinneret glands. These glands are located at the tip of the abdomen; therefore, they are also called abdominal glands.