spider

蛛 is composed of 虫 (insect) and 朱 (vermilion). 朱 depicts a tree with a mark painted on its trunk. In order to make the mark easy to see, it was usually a large red dot. Therefore, 蛛 conveys the idea of a round-shaped creature. This creature is able to spin silk from its rounded, swollen abdomen to weave a web and catch other insects as food.