XVIII. 



NOTES OX LEPIDOrTERA OBSERVED IX HERTFORDSIimE. 



By A. E. GiBBs, F.L.S. 



Read at IVatford, I8th April, 1893. 



It was only on the flay of the last meeting of oui' Society that I 

 accepted the post of Recorder of Lepidoptera occurring in Hertford- 

 shire. The short time which has ekipsed since then has given me 

 very little opportunity of collecting information from observers in 

 different parts of the county, and I am therefore placed at some 

 disadvantage in presenting my first report, which I hope may be 

 the forerunner of an annual series. 



The Clouded-Yellow Butterfly (Colias edusa). — The year 1892 

 has been chiefly memorable entomologically for the extraordinary 

 abundance of the cloiided-yellow butterfly, Colias edusa, for not 

 since 1877, which will long be remembered as the great edusa year, 

 have we been favoured with such a profusion of this beautiful 

 insect. The fact has long been noted that in some years particular 

 species of insects are extremely plentiful, and then for a time 

 seem quite to disappear until another prolific season comes round, 

 "when they may again be seen everywhere. 



AVe have no insect in our British fauna more uncertain in its ap- 

 pearance than edusa. Sometimes for years it may be sought for in 

 vain, and then comes a season like that of last year, when it might 

 be taken on almost any bright day. A writer in the ' Entomolo- 

 gist' (1878, p. 54), referring to the appearance of the insect in 

 1877, gave the dates previous to that vear in which it had been 

 recorded, as follows:— " 1804, 1808, 18il, 1825 (one record), 1826 

 (very abundant), 1831 (plentiful), 1833, 1835 i^both species [edusa 

 and hyale~\ common), 1836 (common), 1839 (common, many in 

 June), 1843 (abundant), 1844 (very common), 1845 (scarce), 1847, 

 1848 (one record), 1851 (one record), 1852, 1855 (common), 1856 

 (common), 1857 (very common, recorded to November 18th), 1858 

 (very common, particularly so in June, also to November 7th), 

 1859 (very abundant), 1861 (scarce), 1862, 1865 (common), 1867 

 (several), 1868 (common, but hyale much more so), 1869 (several), 

 1870 (scarce), 1871 (one record), 1872 (not uncommon), 1875 

 (very common), 1876 (common)." I have looked through the 

 volumes of the same magazine subsequent to that date, and find 

 that, with the exception of the years 1890 and 1891, the appearance 

 of edusa was recorded every season. In some years it was evi- 

 dently scarce, only a few stray captures being reported, while in 

 other years it was fairly common. It was most plentiful in 1879, 

 1883, 1884, 1885, and 1892. In the fifteen years, 1878 to 1892, 

 there were thus five years in which, though it may not have been 

 freely taken over a large area, it was not a rarity in the south of 

 England, while the remaining ten years are marked by the capture 

 of a few specimens only, and in some cases its absence from likely 

 localities such as the New Forest is commented on. 



