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Key to Identifying Caterpillars that Damage Avocado in California

This key will help you identify the larvae of moths that damage avocado in California. Other Lepidoptera species that are found only occasionally are not included. Ask your farm advisor or agricultural commissioner for help in identifying specimens that do not fit the key.

Parts of a caterpillar useful in identifying the species
Identifying parts of the caterpillar

The features used in the key can be seen with a good hand lens, but you may need a low power microscope to see certain features on small larvae. The key works best for specimens in the third instar or larger; some characteristics, such as the number of prolegs and color markings, can be different in very young larvae.

Read both descriptions and compare the specimen with the drawings provided before proceeding. After you arrive at a name, compare the specimen with the appropriate caterpillar photos and description. Take several specimens through the key individually; your monitoring sample may include more than one species and different age groups of one species.

Key to caterpillars


Two pairs of prolegs on abdomen, on abdominal segments 6 and 10:
Prolegs on abdomen
Omnivorous looper
Four pairs of prolegs in middle of abdomen, on segments 3, 4, 5, and 6:
Abdominal prolegs
See 2. below


Black line on thoracic segment 1, above first pair of true legs:
Black line on thorax

Western avocado leafroller (Amorbia)
Black line absent on thoracic segment:
Black line missing

Orange tortrix

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