MIGRATION AND DISPERSAL OF INSECTS : LEPIDOPTEEA. 71 



common, as also was C. edusa), 1858 (common), 1859 (one record), 

 1867 (one record), 1868 (very abundant, edusa was not common), 1869 

 (one record), 1870 (scarce), 1872 (common, not so edusa), 1875 (abmi- 

 dant), 1876 (common). C. edusa was abmidant in 1801, 1808, 1811, 

 in 1825 (one), 1826 (very abmidant), 1881 (plentiful), 1833, 1835 (both 

 species 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 in June, also to November 7th), 1859 (very abundant), 

 1861 (scarce), 1862, 1865 (common), 1867 (several), 1868 (common, 

 but C. lujale much more so), 1869 (several), 1870 (scarce), 1871 (one 

 record), 1872 (not uncommon), 1875 (very common), 1876 (common). 

 In 1877, 0. edusa swarmed from Orkney (W. Tait) to Land's End 

 (Miller), and from Pembroke (Barrett) to Lowestoft (Laddiman). The 

 spring abundance was marked about the middle of May, chiefly in the 

 south and west, and by the end of the first week of June the insect was 

 pretty well distributed. Continuous broods were developed throughout 

 the summer and imagines emerged in the open until November, and yet 

 in 1878, the only records appear to be three imagines seen on April 

 18th, in Beading and Oxford, three others at Ryde, Isle of Wight, on 

 April 22nd, one on May 18th, in one of the north London suburbs, 

 and in the autumn scarcely a specimen was observed, suggesting that 

 the few that survived the winter were not sufficiently powerful to 

 propagate with any degree of success. In 1879 immigrant 0. edusa 

 were observed in May and June, but the wet weather must have 

 decimated the larvse, as the autumnal emergence was only abundant 

 in a few places on the south and south-eastern coasts. The most 

 recent occasion on which both species appeared in the same year took 

 place in 1892, when, during the first week of June, the sudden appear- 

 ance of specimens was almost simultaneously announced from a 

 majority of the English counties, C. edusa being, however, much more 

 common than ( '. Jnjale. These, which were without doubt immigrants 

 —for experience suggests that our climate is unsuited to the larvte of 

 this species during the Avinter (see, Ent. Fwcord, vii., pp. 250-253) — ■ 

 soon laid their eggs, and, by the end of July, their progeny began to 

 emerge, and our clover-fields became quite brilliant with vast numbers 

 of both species. Along the Mediterranean littoral, Avhere the climate 

 is so favourable to the existence of many species, C. edusa is to be 

 found in abundance every year, a succession of broods occurring, 

 whilst the almost entire absence of cold weather does away with the 

 necessity for prolonged hybernation. From these centres it would 

 appear to spread, sometimes in vast numbers, so as now and again to 

 reach our shores, or even to Scandinavia, but more frequently in 

 smaller numbers, its dispersal being confined to the southern countries 

 of Europe, where the species has the greatest chance of existence. 



Bringing its southern habits to England when it immigrates, it 

 lays eggs Avhich in due course produce a summer emergence in 

 July and August, the females of this brood immediately laying their 

 eggs as they would have done in the warmer climes from which their 

 parents came. The caterpillars emerge from the eggs, and for a short 

 time all goes on well enough, and a fresh lot of imagines may even 

 emerge in October and November and the females lay their eggs, but 



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