2.One can tell the difference almost at a glance for the spider always has eight legs and an insect never more than six.
解读:主谓宾+原因状语(省略句)
an insect never more than six
应该理解为昆虫只有六条腿而不是昆虫绝不多于六条腿,全句翻译如下:
翻译:谁都可以一眼就看出蜘蛛与昆虫不同,蜘蛛都是八条腿,而昆虫最多只有六条。

2.One can tell the difference almost at a glance for the spider always has eight legs and an insect never more than six.
解读:主谓宾+原因状语(省略句)
an insect never more than six
应该理解为昆虫只有六条腿而不是昆虫绝不多于六条腿,全句翻译如下:
翻译:谁都可以一眼就看出蜘蛛与昆虫不同,蜘蛛都是八条腿,而昆虫最多只有六条。