ABSTRACT
Aphids feed from sieve elements located deep inside plants which makes it challenging to observe details of the feeding process. The electrical penetration graph technique solves this problem and today this method is widely used to study phenomena such as plant resistance, the effects of insecticides on aphid feeding, and the relevance of individual salivary proteins on aphid-plant interactions. Further techniques have been developed to study the uptake and transmission of phytopathogenic viruses. Artifi cial feeding was developed in 1930 and was improved in the 1960s so that the nutritional needs of aphids could be determined. Aphids can also be used as tools to access the sieve elements of plants, e.g., to study the composition of sieve element sap and to measure electrical signals in the plant which can be triggered, e.g., by caterpillar feeding.
