A pronounced variation in the time taken by hopper bands of Nomadacris septemfasciata, Serv., to become adult swarms in different localities in the Nyasaland Protectorate during the four breeding seasons from 1932 to 1936, led to an investigation and comparison of certain climatic factors occurring during the critical months of hopper development at a number of stations where such variation had been particularly noticeable.

It was found that temperature and percentage relative humidity appeared to have considerable influence on the rate of development of the hopper bands, and that the quiescent nature of the bands in certain areas in some years, together with the unexpectedly small adult swarms that matured from these bands, seemed to be correlated with these same factors. It was noticeable that conditions during the first season, when development was generally normal, were somewhat hotter and drier throughout the country than in the later years and that, in most places, a marked increase in humidity usually accompanied by a decline in temperature was recorded each year up to 1936. In certain areas where hopper development occurred each year without much variation in length of time or intensity, such as the lower Shire River Valley, temperatures and humidity were found to have fluctuated only slightly from year to year.