Periodical Appearance of certain Insects. 247 



Art. X. On the Periodical Appearance of certain Insects. By 

 J. H. Davies, Esq., Lieut. R. M., late Curator of the Museum 

 of the Portsmouth Philosophical Society. 



Sir, 



That certain insects occasionally appear very numerously, 

 and are again for a period comparatively rare, has been long 

 noticed by entomologists, and some instances are so striking, 

 as to excite the attention of the most incurious observers ; but 

 I am not aware that any attempt has been made to ascertain 

 whether the intervals are stated or irregular, or how far they 

 are influenced by the temperature of the seasons. The observ- 

 ance of these interesting facts may perhaps form a desirable 

 feature in your proposed Perennial Calendar of Nature : in 

 the mean time, the prevalence of certain insects, as they came 

 under my observation in this neighbourhood (Portsmouth) 

 during a few seasons past, may perhaps be worthy of note. 



1825. — Papilio cardui. Painted Lady Butterfly, is one of this 

 tribe, mentioned as an occasional visitant. This year I found 

 a field of red clover completely covered by them ; since when 

 they have been scarce. Papilio cardamines. Orange Tip, 

 was also particularly numerous. The genus Chrysomela was 

 very plentiful : a long hedge near Milton was crowded with 

 the C. aucta, C. Marsham/, and others. I have since visited 

 the same spot without success. 



1826. — Papilio crataegata. Black-ribbed Butterfly, is rather 

 a local insect. In the previous summer I met a scientific 

 tourist from Suffolk, who informed me that he had visited 

 Hants to procure this insect, which he understood was here 

 plentiful : we searched for it several days to no purpose ; but 

 this year they were more numerous than even the common 

 Cabbage White, abounding in every field: since then very 

 scarce. The Musco. genus unusually plentiful. Great num- 

 bers of- Cerambyx violaceus were also taken. This year was 

 marked by the prevalence of that pest to fruit trees, Phalse^na 

 Neustria, Lackey Moth. In the spring the boughs were 

 covered with the webs of the larvae ; and so plentiful was the 

 moth in the autumn, that more than one hundred flew into my 

 study window on one evening : they have not since appeared 

 in such numbers. 



1827. — Papilio A'rgu5, Argus Butterfly, studded the fields 

 with its blue wings in unusual numbers. Hister quadru- 

 maculatus, of which I had previously taken few specimens, 

 now covered Southsea Common, so that many were crushed 

 under foot at every step; with them was Carabus caerules- 

 cens, in equal numbers : and between the two a deadly war 



