什么是昆虫(中英）

现在，人类已经知道的动物大约150万种，其中昆虫大约100万种。昆虫这么多，所以人类与它们相伴也成为必然。

那么，什么样的动物才是昆虫呢？在动物分类中，昆虫属于“昆虫纲”。昆虫纲，又叫“六足纲”，主要特征就是它们的成虫，注意是“成虫”，具有三对足，也就是六个足。

高等动物，受精卵在母体内发育，胚胎发育过程你是看不到的。产出来了，才是我们看到的它们的样子。

昆虫的受精卵，不在母体内，而是在母体外，在自然界里发育，我们人也经常看到。但那不是他们的成虫。

所以，昆虫有三对足，一定是指它“长大成人”了，到了“成虫”阶段了。

此外，绝大多数成虫都有翅，两对，也有一对的。当然，个别的也有没翅的。

What Are Insects?

Currently, humans have identified about 1.5 million species of animals, with insects accounting for roughly 1 million of them. Given their sheer numbers, it is inevitable that humans share this planet with them.

But what exactly defines an animal as an insect? In biological taxonomy, insects belong to the Insecta, also known as Hexapoda (meaning "six-legged"). The primary defining feature is that their adults—and note the emphasis on adults—possess three pairs of legs, totaling six.

In higher animals, fertilized eggs develop inside the mother's body, so embryonic stage remains hidden from view. They only take on their familiar forms once born.

Insect fertilized eggs develop outside the mother's body, right there in nature, and we often get to see them. However, what we see at this stage are not adult insects.

Therefore, the rule that "insects have three pairs of legs" strictly applies only when they have reached full maturity, or the "adult" stage.

Additionally, most adult insects have wings. Typically, they have two pairs, though some species have only one. Of course, there are always a few exceptions that are entirely wingless.

* “六足纲” 翻译为了生物学上的标准术语 Hexapoda。
* “长大成人” 在英文里用 reached full maturity 会比直译 "grow up to be a person" 更准确且符合科普语境。