of the Oil Beetle, Meloé. 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 Meloés and the adult parasites of vertebrated animals, 
the Pediculi 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 Meloé escapes from the egg, and are not essential, or true 
imago insect forms. 
It is necessary thereforé 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 Meloé. The larva of 
the common blister-fly, Lytta vesicatoria, as most accurately figured by 
Brandt}, is almost identical in form with that of Meloé, 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 egg it is at first 
yellow, like Meloé, 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 Meloé cicatricosus, M. proscarabeeus 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 Melittet, and by myself on Osmia spinulosa, resembled the yellow 
larvae of Melo 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 Andrenide, especially on An- 
drena fuscata, captured in the spring on Hampstead Heath, where different 
Species of the adult Meloés are often abundant. In April 1841 he found 
similar black larve in such profusion within the flowers of the buttercup 
* Nouv. Suites à Buffon, Aptéres, tome iii. 1844, p. 360. 
t Brandt und Ratzeburg, Darstell. und Beschr. der Thiere, Berlin, p. 129, pl. 19. 
* Monographia Apum Angl. vol. ii. p. 168. 
VOL. XX, | 2v 
