76 



But to return to its appearance in this country ; it has been 

 asserted that if the imagines taken were immigrants we should 

 expect to find them, first on our Kentish coast, and then 

 afterwards crossing the island by the midland counties, and 

 lastly in our western districts and Ireland. Now, if the moths 

 before starting on a journey sought the shortest sea route, as 

 is said to be proverbial with our neighbours — the Frenchmen, 

 I could well understand that Calais to Dover would suit them 

 admirably, and that they would subsequently be found 

 spreading across this country by the lines indicated. But 

 unfortunately for this argument we have not one word in all 

 the evidence regarding migration to indicate that such move- 

 ments originate in the districts nearest to us, or that this short 

 sea route is one followed by Lepidoptera observed in a mi- 

 gratory condition ; but, on the contrary, we find that what 

 few records we have tend rather to show that they originate 

 in the more distant countries to the south of us (vide Vanessa 

 cardiii), and are of wide expanse. A glance at the map will 

 show that any widespread northerly movement from those 

 regions would embrace the whole of the British Islands, as 

 well as North Germany, Denmark, Sweden, etc., where its 

 fitful occurrence appears to be on a par with that observed 

 here. 



There is yet another moth that must claim our attention by 

 reason of its fitful appearance. Plusia gamma, L., is one of 

 our commonest if not our commonest species; it is present 

 with us every year in greater or less numbers, and similarly 

 occurs throughout the Continental region. In many respects 

 its cases of abnormal abundance closely resemble those of 

 Vanessa cardui ; the two species appear to have the habit of 

 suddenly coming upon us together, in multitudes, after an 

 apparent season of scarcity. Only last year a case was 

 mentioned at one of our meetings by Mr. Carrington, who 

 told us that he had collected several times weekly over a 

 certain part of Surrey, but had not up to ist June met with a 

 single example of either species. On that day one V. cardui 

 was captured, and on the 3rd both it and P. gamma were seen 

 in hundreds ; and further, that both species gradually dis- 

 appeared within a week, and were afterwards to be seen only 

 occasionally. We do not, however, find that gamma was 

 generally unusually common last year ; nor had it been so in 

 the previous autumn, although it had been observed in vast 

 multitudes in many places, chiefly in the South of England 

 in the preceding May and June. 



In 1883 we also appear to have had an unexpected visi- 



