of the Oil Beetle, Me\o^. 323 



been advanced, so recently as 1844, by M. Gervais*. This error has arisen 

 from these able naturalists entirely overlooking the principles of development, 

 and from their being misled by the great similarity of structure which exists 

 between these young Meloes and the adult parasites of vertebrated animals, 

 the Pedkuli and Nirmi. These parasitic Aptera, properly regarded, are inferior 

 or larval types of Articulata, in which organization is not carried beyond that 

 stage at which the Meloe escapes from the e^g, and are not essential, or true 

 imago insect forms. 



It is necessary therefore that we should first show to what species and 

 genera of true insects this parasitic type of organization in the larva state 

 belongs, and then endeavour to ascertain what general relations its peculiari- 

 ties of structure bear, in whole or in part, to the habits of the individual spe- 

 cies. This form of larva is not restricted to the genus Meloe. The larva of 

 the common blister-fly, Lytta vesicatoria, as most accurately figured by 

 Brandtf, is almost identical in form with that of Meloe, the chief structural 

 difference being that Lytta has only one instead of two pairs of caudal setae. 

 Lytta however differs in colour. When it comes from the eg^ it is at first 

 yellow, like Meloe, but quickly assumes a darker hue, and soon afterwards a 

 deep black, excepting only on the first abdominal, and the meso- and meta- 

 thoracic segments, which are yellow, with a dark patch on each side of the two 

 latter. The larvae of Meloe cicatrlcosus, M. proscarahceus and M. violaceus 

 never acquire this darkened colour, but are always of a yellow or light orange. 

 The larva found by Mr. Kirby on Andrena fuscata, and described by him as 

 Pediculus MeUttoe%, and by myself on Osmia spinulosa, resembled the yellow 

 larvae of Me/oe in almost every particular excepting in colour; and Mr. F.Smith, 

 to whom I have referred in my former paper, has, as I have there stated, taken 

 similar black larvae in great profusion on the Andrenidce, especially on An- 

 drena fuscata, captured in the spring on Hampstead Heath, where different 

 species of the adult Meloes are often abundant. In April 1841 he found 

 similar black larvae in such profusion within the flowers of the buttercup 



* Nouv. Suites k BufFon, Aptferes, tome iii. 1844, p. 360. 



t Brandt und Ratzeburg, Darstell. und Beschr. der Thiere, Berlin, p. 129, pi. 19. 



X Monographia Apum Angl. vol. ii. p. 168. 



VOL. XX. 2 u 



