Like most true bugs (order Hemiptera), the citrus flatid planthopper (Metcalfa pruinosa, Flatidae) feeds on plant sap using piercing/sucking mouthparts. This particular insect is partial not only to citrus plants, but also a wide range of other woody plants including riverbank grape (Vitis riparia, Vitaceae). In the photo above you can see the planthopper’s proboscis piercing the grape vine, drinking up the sugary sap that runs through the phloem. While many Hemipterans are serious plant pests, this planthopper is generally not a significant threat.
A number of other Hemipterans within the suborder Auchenorrhyncha are commonly known as -hoppers. In addition to planthoppers (superfamily Fulgoroidea) there are also leafhoppers (family Cicadellidae), treehoppers (family Membracidae), and froghoppers (family Cercopidae). You can easily tell why they’re called hoppers if you approach one: it will quickly hop out of sight in the blink of an eye, almost as if it’s spring-loaded.