“Bug” vs. “Insect” We tend to use the word bug loosely for any very small creature with legs. However, a true bug is defined as belonging to the order Hemiptera. These creatures characteristically have tough forewings and lack teeth, such as beetles. True bugs have a stylet (a mouth shaped like a straw) that they use to suck juices from plants. Insects belong to the class Insecta and they are characterized by three-part bodies, usually two pairs of wings, and three pairs of legs, (e.g., bees and mosquitoes). Arthropods (spiders, ticks, centipedes, etc.) is a separate phylum from bugs and insects. All of this does not mean that you are wrong to call various insects bugs; because of the common usage of this meaning, it is certainly acceptable. Don't Get Mixed Up Again! Get Dictionary.com tips to keep words straight ... right in your inbox. Email address* Valid email addressEmailThis field is for validation purposes and should be left unchanged.