Gerling, D., & Bar, D. 1971 Reciprocal host-parasite relations as exemplified by Chrysomphalus aonidum (Homoptera: Diaspididae) and Pteroptrix smithi (Hymenoptera: Aphelinidae).. Entomophaga 16: 37-44.

Notes: The parasite Pteroptrix smithi (Compere) prefers to oviposit in hosts (Chrysomphalus aonidum L.) that are at least 5 weeks old. Parasitization of two week old hosts is possible, but only few parasites reach maturity, and the developmental duration is lengthened by about one third. The sex ratio with both large and small hosts was usually 1:2, whereas the average number of emerging parasites varied from 1.9 for 2 week old hosts to 3-4 for 5 week old ones. Non-ovipositing scales that are attacked by the parasite will fail to reproduce and ovipositing ones will only produce part of their potential progeny. Other externally observable changes in the young parasitized host include the formation of a thinner scale cover that differs in coloration and size from the normal one.