6064 



Insects. 



which I was enabled to make last autumn through the kindness of 

 the Messrs. Wilson. 



In April, 1856, I received, from Perthshire, eggs of Petasia nube- 

 culosa, Brephos Parthenias and Semioscopis Avellanella — all very 

 interesting species to the systematic entomologist, from the positions 

 they appear to occupy on the limits of the respective tribes to which 

 they belong, each apparently possessing the characters of two of the 

 principal divisions of the Heterocerous Lepidoptera. These involved 

 affinities are fully borne out by the characters of the ova, which have 

 been too much neglected as an aid to classification. Thus, the eggs 

 of the Petasia are spherical and ribbed, like those of the Noctuina; 

 and the young larva, when first disclosed, arches the central segments 

 slightly in walking, like nearly all the larvae of the Noctuina, before 

 their second moult. The eggs of Brephos Parthenias, which Guenee 

 places at the end of his first section of the Noctuina, are oblong-oval, 

 smooth, and resemble the eggs of most of the Geometrina ; while 

 those of Semioscopis Avellanella are flat and scale-like, indicating a 

 close aflinity with the Tortricina. The young larvae of Petasia nube- 

 culosa were disclosed from the egg about the middle of May, and 

 were then bluish-gray, with small dark tubercles and an amber- 

 coloured head. They were very restless at first, and it was some time 

 before they commenced to feed. They changed their first skin in 

 about fourteen days, spinning a ^silken carpet on the leaf, in which 

 they fastened their prologs for security of position, and then appeared 

 of a pale green, with three whitish lines, minute black tubercles, and 

 translucent green head ; the thoracic feet and a spot upon each of the 

 prolegs black. They still looped slightly in walking, resting solitarily 

 on the under sides of the birch leaves, with their heads stiffly re- 

 curved, like the larva of Endromis versicolor, and dropping, when 

 suddenly alarmed, by a silken thread, which they used for the purpose 

 of regaining their position when the supposed danger was over. In 

 disposition they were most pugnacious and irritable, hitting and biting 

 each other whenever they came in contact, and wandering restlessly 

 about when disturbed. In consequence of these habits, several of 

 them died from the wounds they received from their companions. 

 The second moult was completed in eleven or twelve days, when the 

 black tubercles became pale whitish yellow. After the third moult, 

 which was again accomplished on the fourteenth day, the young larvae 

 were pale yellowish green, the hair-warts sulphur-yellow ; an oblique 

 lateral streak on the fourth segment, and a transverse bar on the 

 twelfth segment, of the same colour; head unicolorous green; tlio- 



