DeBach, P., Hendrickson, R.M., & Rose, M. 1978 Competitive displacement: extinction of the yellow scale, Aondiella citrina (Coq.) (Homoptera: Diaspididae), by its ecological homologue, the California red scale, Aonidiella aurantii (Mask.) in southern California.. Hilgardia 46: 1-35.

Notes: History and documentation of extinction; possible explanations for the extinction of yellow scale in southern California; laboratory tests of yellow and California red scale relative to competitive displacement; experimental testing of the hypothesis of extinction of yellow scale by competitive placement; results indicate that yellow scale is able to survive on a number of host plant species in various countries on which California red scale has not been recorded, so ultimate worldwide extinction by competitive displacement outside the native range is probably impossible.