VII. 



A NATURALIST'S CALENDAR FOR MID-HERTFORDSHIRE. 



By J. J. Willis. 

 (Communicated by the President.) 

 B.ead at Watford, 6th May, 1892. 



Hattng taken Phenological Observations during the past fourteen 

 years in accordance with a calendar of phenomena recommended 

 for observation by the Royal Meteorological Society, and the 

 calendar having now been reduced by Mr. E. Mawley, the 

 Phenological Recorder to the Society, from 79 species of plants, 

 11 of insects, 21 of birds, and one amphibian, to 13 species 

 of plants, 5 of insects, and 5 of birds, it seems desirable to bring 

 together, in a condensed form, the facts already ascertained. 



The observations were taken at Harpenden, in Mid-Hertford- 

 shire, 51° 48' N. Latitude, and 0° 21' W. Longitude, and have 

 extended over the fourteen years 1878 to 1891 inclusive, but as 

 the list of phenomena to be observed was altered and extended by 

 the Meteorological Society between 1882 and 1883, the obser- 

 vations of the same species do not in every case run through the 

 fourteen years. 



The record has therefore been divided into two equal periods of 

 seven years each, which in itself will, I think, be found of value ; 

 the earliest and the latest date and year within each of these 

 periods is also given. 



The first column of figures in the table gives the total number 

 of observations made for each species of plant, insect, and bird ; the 

 next four columns record the earliest and latest date at which each 

 phenomenon was noted within the two periods of seven years each ; 

 the next column gives the mean dates of all the observations 

 obtained at Harpenden ; and the last column in the table shows 

 the difference by number of days between the mean dates of most 

 of the phenomena in Mid-Herts and in South-west Herts, the dates 

 for that district being those given by Mr. Hopkinson for the 

 neighbourhood of "Watford, as the result of his observations ex- 

 tending over the twelve years 1875 to 1886 inclusive.* 



Referring to the data given in the table we find that in the first 

 seven years, 1878 to 1884, the season of 1882 was the most 

 forward, while that of 1879 was the most backward. 



In the second seven years, 1885 to 1891, there were two seasons 

 giving very early dates, namely those of 1885 and 1890, while the 

 most backward seasons in the same period were those of 1888 and 

 1891. 



As a rule, in the second seven years the earliest dates of 

 flowering of the various species of plants, and the first appearance 

 of the insects and migratory birds, were later than during the first 



* "A Naturalist's Calendar for the South-west of Hertfordshire." — 'Trans. 

 Herts. Nat. Hist. Soc.,' vol. v, p. 129 (1889). 



