昆蟲在分類學上屬於昆蟲綱（學名Insecta），是世界上最繁盛的動物，已發現超過100萬種[1]。其中單鞘翅目（Coleoptera）中所含的種數就比其它所有動物界中的種數還多。昆字原作䖵[2]。
昆蟲的構造有異於脊椎動物，它們的身體並沒有內骨骼的支持，外裹一層由幾丁質（英文 chitin）構成的殼[3]。這層殼會分節以利於運動，猶如騎士的甲胄。昆蟲的身體會分為頭、胸、腹三節，有六隻腿，複眼及一對觸角。昆蟲有脂肪體，成分類似脊椎動物的脂肪組織，但作用不同，主要為代謝功能，類似脊椎動物的肝。
昆蟲在生物圈中扮演着很重要的角色。蟲媒花需要得到昆蟲的幫助，才能傳播花粉。而蜜蜂採集的蜂蜜，也是人們喜歡的食品之一。在東南亞和南美的一些地方，昆蟲本身就是當地人的食品[4]。
但昆蟲也可能對人類產生威脅，如蝗蟲和白蟻。而有一些昆蟲，例如蚊子，還是疾病的傳播者。
有一些昆蟲能夠藉由毒液或是叮咬會對人類造成傷害，例如虎頭蜂在有人入侵地盤時會以螫針注入毒液等。
Insects belong to the taxonomic Insecta (scientific name Insecta), is the world's most prosperous animals have been found more than one million kinds [1]. Where several single Coleoptera (Coleoptera) contained more than the number of species on all the other animals in the community. Queensland word original 䖵 [2].
Structure insects different from vertebrates, their bodies did not support the skeleton inside, wrapped in a layer of the shell chitin (English chitin) constitute [3]. This layer of the shell section will facilitate the movement, like the knight armor. Insect's body will be divided into head, thorax, abdomen three have six legs, compound eyes, and one pair of antennae. Insect fat body fat composition similar to vertebrate tissue, but the effect is different, mainly for metabolic function, similar to the vertebrate liver.
Insects play a very important role in the biosphere. Entomophilous flowers need help insects to spread pollen. The bees collect honey, but also people like one food. In some parts of Southeast Asia and South America, the insect itself is local food [4].
But insects also may pose a threat to humans, such as locusts and termites. And there are some insects, such as mosquitoes, or disseminator of the disease.
