188 A. E. GIBBS — NOTES ON LEPIDOPTERA 



Last season edusa appears to have been first seen in the '^QVi' 

 Porest on the 24th of May, whence it is inferred that our visitors 

 landed on the coast of Hampshire, and from there spread them- 

 selves out over the country. After this date specimens were 

 observed in many widely-scattered localities. They no doubt 

 deposited their eggs on clover and other leguminous plants, their 

 progeny appearing as perfect insects in August, in which month 

 edusa was recorded from every English county except Northum- 

 berland, Durham, Cumberland, Westmoreland, Huntingdon, and 

 Rutland.* In some of these counties it was probably present but 

 unnoticed. It was far more plentiful, as might naturally be ex- 

 pected, in the south than in the north of the country, though 

 several individuals are recorded as having been taken in Scot- 

 land. 



Colias edusa appears to be really a native of the lower regions of 

 the Swiss Alps, where it generally produces a single brood and 

 hybernates, as does the brimstone butterfly with us. Thence 

 the perfect insects are occasionally, from causes not very well 

 understood, driven northwards, and so reach our shores, but fail, 

 probably from climatic reasons, to establish themselves. 



I cannot now attempt to investigate at any length the cause 

 of these spasmodic appearances and disappearances, and it must 

 suffice to say that the generally-accepted theory is that in years of 

 unusual abundance a migration has taken place from the Continent 

 about the month of May, and that the immigrants have laid eggs 

 from which the numerous August brood has sprung. 



Miss Ormerod, in her ' Heport of Observations on Injurious 

 Insects' for the past year (1892, p. 31) alludes to the appearance 

 of edusa. Every entomologist will be pleased to hear that so 

 competent an authority as Miss Ormerod does not rank edusa as an 

 injurious insect, but she sounds a note of warning with regard to 

 it, pointing out that the caterpillars when under supervision have 

 been found to be voracious feeders on trefoil and white clover, and 

 "may prove to be an infestation requiring attention." 



During 1877, the year in which edusa was particularly abundant, 

 I took a great many specimens both of it, and its congener, 

 C. hyale, in the neighbourhood of St. Albans. Its favourite place 

 of resort then was a piece of nursery-garden, and the steep banks 

 of the road, now the site of Mr. Sander's orchid establishment. 

 The pale variety of edusa (Jielice) was also taken at the same spot. 

 The only other information that I have been able to find with 

 regard to its appearance in Hertfordshire in 1877 is a note by 

 Mr. Arthur Cottam, which was printed in our Transactions,! and 

 which states that it then visited us in unusual numbers, the 

 localities mentioned being St. Albans, Watford, and Bushey. In 

 1885, when it appears to have been more plentiful than in any 

 other year between 1877 and 1892, I find in the 'Entomologist' 

 the following commuuication from Mr. G. H. Tite, Amwell House, 



* 'Entomologists' Record,' vol. iv, p. 16. 



t ' Trans. Watford Nat. Hist. Soc.,' Vol. I, p. 239. 



