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6. — !N'oTES ON THE Observation of Insects in Connexion with 

 Investigations on Seasonal Phenomena. 



By Arthur Cottam, F.E.A.S. 



[Read 13th May, 1875.] 



The Ecport prepared by Mr. K. McLachlan, F.L.S., for the 

 Meteorological Society, as to insects proper to be observed in 

 connexion with seasonal phenomena, temperature, etc., is so 

 excellent that there is but little I can add to it. The selection 

 of insects made by Mr. McLachlan as suitable for the purpose 

 appears to me a veiy judicious one, and although the number is 

 small — eight only — I believe these will be found to be amply 

 sufficient. They are all insects that will be known to most 

 persons who are at all in the habit of observing natural objects, 

 or which can, at all events, be readily identified by any one 

 desirous to make them out. There is just a possibility, but hardly 

 a probability, of making a mistake between the two white cabbage 

 butterflies. It is not always safe to trust to the difference in 

 size, as I have often seen specimens of the large one as small as, 

 or even smaller than, normal specimens of the small white 

 cabbage butterfly. There is a greater likelihood of mistaking the 

 green-veined white for the smaller cabbage white, unless the 

 markings on the underside are carefully examined. The colour 

 and markings of the two cabbage butterflies are somewhat similar, 

 but the underside of the green-veined white is quite distinct. 

 The green- veined white often appears quite as early as the small 

 cabbage, is as nearly as possible the same size, and it also feeds 

 upon one of the cabbage tribe — Brassica Napus, after which it is 

 called Puris Napi. 



The meadow-brown butterfly is at the time it makes its 

 appearance, towards the end of June, very much the commonest 

 of all the brown butterflies. There are one or two other species 

 out at the same time, but they have to be sought for in woods, 

 or, at all events, are not to be found in every meadow, and in 

 fact everywhere, as the moadow-broAvn usually is. 



Mr McLachlan suggests that occasional appearances in unusual 

 numbers of any insects should be noted. These occasional appear- 

 ances are one of the greatest puzzles to entomologists, and at 

 present are not in any way satisfactorily accounted for. One of 

 the butterflies referred to, the pale clouded yellow, was very 

 abundant in 1846, and scarce from that year till 1868, when it 

 was positively commoner than almost any other butterfly all along 

 the south coast. At Margate and Westgate I saw it flying twenty 

 or thirty at a time, and I could without difficulty have taken a 

 couple of hundred in the course of a week. Probably not one 

 in twenty of all that there were, were taken, and yet hardly a 

 specimen has been seen since. Vanessa Cardui was also common 

 that year; and in 1872, Vanessa Anfiopa, the rare C'amberwell 

 beauty, was tolerably abundant, but only one or two stray speci- 

 mens have been seen or taken since. 



