The distribution of attack by a shoot-fly larva.
Abstract
The following is substantially the author's summary of this account of further studies in Kenya [cf. RAE A 57 1599]. The distribution of eggs laid by Hylemya arambourgi Séguy on barley shoots in experimental plots is analysed briefly. The distribution was patchy, but there appeared to be sufficient eggs laid to permit attacks on all available shoots. The distribution of attack on plants with only one shoot showed an unpatterned aggregation, reflecting a more or less random distribution of groups of attacked plants. This distribution became more normal as the attack continued. In tillered plants, the distribution of attack among plants with similar numbers of shoots was Poisson, although the origin of this distribution was essentially complex. There was a tendency for higher rates of attack on plants with numerous tillers, which can be interpreted as the result of greater concentration of attack on individual plants, larval transference within plants, traumatic response to early attack, or, most probably, to a combination of all three. These facts, taken in conjunction with previous findings on variation in susceptibility and the different shoot-susceptibility content of individual samples, are believed to offer a satisfactory explanation of variation in the number of attacked shoots. It is not considered feasible or worthwhile for practical data-processing to attempt to model this relation more accurately.