Some Difficulties in determining by Means of Field Samples the true Value of Parasitic Control

Abstract

The author points out the following cautions in sampling: (1) A parasite that attacks full-grown host larvae would not be represented in a sample of small larvae. (2) The degree of control of fluctuating host and parasite populations can only be obtained by a series of samples taken at intervals over an extended period of time. (3) In sampling host eggs consideration must be given to the duration of the egg stage when unparasitized, the age of the egg when attacked by the parasite, and the duration of the egg stage when parasitized. (4) A parasite may continue its attacks through several generations on the same host stage while the host is in diapause. (5) Samples must represent the differing availability of the host so that individuals readily available to the parasite as well as those not readily available are represented.