316 INSECT TRANSFORMATIONS. 



chapter. In the instance of the clear underwing 

 (JEgema asiliformis, STEPHENS), we discovered a 

 brood of above a dozen of the pupae in the trunk of a 

 black poplar ; but though, from feeding on the wood 

 of the tree, the caterpillars must have been well pro- 

 tected from the vicissitudes of the seasons, there was 

 nearly a month between the appearance of the first 

 and the last.* This, indeed, is so very common an 

 occurrence that it is almost superfluous to mention 

 particular instances. 



The moths just mentioned, we may remark, were 

 only observed to appear about noon ;. and many 

 other insects are known to emerge from the pupa 

 only at one particular time of the day, similar to the 

 flowers, such as the goat's-beard (Tragopogon], and 

 the night-flowering cereus (Cactus grandiflorus], 

 which only blow at particular hours. Some insects 

 are produced at sunrise, others at noon, and others 

 again only at night. Several species are extremely 

 regular in their appearance, such as the orange-tip 

 butterfly (Pontia Cardamines), which is usually seen 

 about the end of April, varying bu.t few days in the 

 course of many years. The various species, also, of 

 May-flies (Ephemerae} are confined in their appear- 

 ance to two or three days ; and those observed by 

 Reaumur appear at no other time than between 

 eight or ten in the evening. Those which we no- 

 ticed on the Rhine in August, 1829, began to 

 appear at sunset, and before morning were all dead. 

 In the great square at Wiesbaden, their bodies were 

 so thickly strewn about that it seemed as if a shower 

 of snow had fallen during the night, their wings 

 being white, and about the size of a broad snow- 

 flake.t 



The pupae of these May-flies, when about to un 



* J. R. t J. R, 



