a n t e n n a
This key can be used to distinguish between three species of Lygus reportedly found in agronomic crops in the Central
San Joaquin Valley of California. Lygus hesperus Knight (western tarnished plant bug) is the predominant species found,
while Lygus elisus Van Duzee (pale legume bug) is observed less frequently. Lygus lineolaris Palisot de Beauvois
(tarnished plant bug) has been reported from the Central San Joaquin Valley, but is rarely found in field crops. Being
able to correctly identify the various Lygus species may improve interpretation of research results or enhance research
progress in areas such as biological control and assessment of economic damage. Studies of overwintering habitat and
intercrop movement will also be facilitated.
Collect lygus bugs using a sweep net or other sampling device. Prior to beginning the identification process, place
specimens in the freezer for at least 24 hours to kill them. Alternatively, they may be placed in ethyl alcohol to kill and
preserve them, but specimens tend to become brittle if stored in alcohol for more than 3-5 days prior to examination.
It is important to work through the field key step by step. Completing Step 8 of the key is extremely important to confirm
the identity of the species in question, especially if the specimen could be an overwintered adult. Terms and morphological
characters are defined in the glossary at the end of this key.
A Field Key to the
Most Common Lygus Species Found in Agronomic Crops
of the Central San Joaquin Valley of California
Use a minimum of 10x magnification and the best lighting available.
Shannon C. Mueller1, Charles G. Summers2, and Peter B. Goodell3
1Agronomy Farm Advisor, UC Cooperative Extension, Fresno Co