134 Mr. J. O. Westwood’s Memoirs 
observations previously made on the economy of the genus, the 
author states that ‘nell’ estate del 1841, mi fu donato dal Signor 
Marchese Carlo Durazzo un insetto innominato col simplice 
inscrizione ‘ Parasita in larva di Farfalle,’ con somma mia sor- 
presa reconobbi in esso una femmina del Sirex gigas ;” and on 
inquiring from Signor Franchi (from whom the insect had been 
obtained), he was informed that “la larva che ha dato recetto 
al parasita é quella del Muchaon. Pero quando si sviluppo lin- 
setto, essa erasi da quindici giorni messi in crisalide ; si crede de 
poter anche asserire di aver veduto un Sirex uscire dalla crisalide 
del Podalirius.’” From these remarks, and the statements of St. 
Fargeau, the Marquis arrives at the conclusion that “le larve dei 
Sireci sono zoofaghe,” proposing a classification of the order requi- 
site for its distribution, in accordance to the supposed Zoophagous 
character of the Sirecide. 
Having in the preceding pages endeavoured to prove the affinity 
of Xiphydria and the Uroceri, as well as to establish the Xylopha- 
gous character of the family formed of these two genera, I have 
deemed it necessary to notice the remarks of the Marquis Spinola 
cited above. 
That the exuvize observed by the Count St. Fargeau lying at the 
side of the pupa of the Urocerus were those of the larva of some 
Longicorn beetle, upon which the Urocerus had parasitically sub- 
sisted, as considered by the Count, admits in my opinion of much 
doubt ; I consider in fact that they were the exuvie of the larva 
of the Urocerus itself. The structure of the head and manducatory 
organs of the latter in fact so closely resemble those of a Longicorn 
larva, that it is not surprising that the Count St. Fargeau should 
have mistaken them for the remains of the larva of a beetle which 
the Urocerus had devoured. It will of course follow that the finely 
pulverised particles of wood found in the burrows of these insects 
are the result of the boring of the Urocerus itself, and not of a 
larva upon which it has subsisted. 
Neither can I consider the statement of the Marquis Spinola as 
more satisfactory in disproving the Xylophagous character of the 
Uroceride. The unsatisfactory mode in which the statement is 
made,—the very doubt of Signor Franchi, whether he had not ob- 
tained Urocerus gigas not only from Papilio Machaon, but also from 
Papilio Podalirius, (thus establishing a case of parasitism of one 
species upon two distinct species of animals, a circumstance of 
very unusual, if not of doubtful, occurrence,) — the well-known 
habits of the Uroceri, and of the two species of Papilio in question, 
