﻿146 JAS. J. SIMPSON — ENTOMOLOGICAL 



humidity. There can be no doubt also that temperature and humidity influence 

 the period of reproduction, and may also modify the length of time occupied in 

 the larval stages. 



After a consideration of the general physical configuration of the Colony and 

 its vegetation, it may be well, therefore, to discuss briefly the main charac- 

 teristics of the climate in so far as these affect the problem in hand. Hitherto, no 

 attempt has been made either to consider the climate of the Colony as a whole or 

 to compare the variations in the different regions. Meteorological observations 

 are now made at a large number of stations in Southern Nigeria, so that it is 

 possible, within limits, to form some general opinion of each of these aspects. 

 The figures on which the following notes are based are compiled from the raw 

 data supplied to the Meteorological Office, but for the arrangement the writer is 

 entirely responsible. It has been considered advisable to prepare and include 

 certain tables in order to avoid lengthy descriptions, and also to present the 

 matter in more concrete form. 



The climate of Southern Nigeria is, broadly speaking, of the equatorial type. 

 By this is meant that there are two fairly distinct seasons, known as the " dry " 

 and the " wet " or " rainy " season ; the latter is often briefly designated as the 

 " rains." The dry season lasts from about the end of October to the beginning 

 of March, but the rainy season, though, properly speaking, occupying the 

 remaining eight months, is again subdivided into the "heavy" and the "light" 

 rains, each with its own maximum. The heavy rains fall during the months of 

 April, May, June and July, while the light rains occupy the other three 

 months. 



A similar state of affairs holds good in the case of the temperature curves, 

 which also have two maxima, the first between the middle of March and the 

 middle of April, and another of a secondary order between the middle of 

 September and the middle of October. 



During the heavy rains the weather is for the most part dull, with occasional 

 sunshine, and the humidity is great. Throughout the dry season the weather is 

 clear and fine, but there are occasional showers. 



The general direction of the wind is from the south or south-west. The wind 

 is consequently full of moisture, but from the end of November to the beginning 

 of March the influence of the Harmattan — a dry wind blowing from the Sahara 

 in the north-east — is very marked. During this period the air is excessively 

 dry and laden with fine particles of dust ; the temperature in the morning and 

 evening is very low, and a misty haze hangs about nearly the whole day. The 

 sun is seldom visible before eight in the morning or after five in the evening, 

 and this haze extends far out to sea. Immediately before and after the rainy 

 season, tornados of terrific force, uprooting large trees and often doing 

 considerable damage, blow in the evenings ; these are accompanied by 

 torrential rains. 



On the whole, the temperature in the shade is not very high, the average 

 maximum temperature being about 91° Fahr., the average minimum about 65°, 

 the mean about 78°, with a daily range of about 26°. The maximum temperature 

 recorded by the thermometer exposed to the full effect of the sun is about 146° 



