Generally people will use "bug" to refer to any arthropod or, more loosely, to several classes of small thing including bacteria that seem animal-like but not b

Generally people will use "bug" to refer to any arthropod or, more loosely, to several classes of small thing including bacteria that seem animal-like but not bacteria that seem plant-like. Generally all of these usages have connotations of being bad but also not very important. For instance someone might refer to the common cold as a "bug" but generally not to Ebola.