96 
SYLVIAD.E. 
would ask, tliat the blackcap and other warblers, possessing 
probably not greater powers of flight, should extend over 
many parts of the sister kingdoms in which the Nightingale 
is unknown ? 
Neither is it reasonable to suppose that Wales, Ireland, 
and the few excluded counties of England, are altogether- 
destitute of a particular insect food necessary to their sub¬ 
sistence, unless we take into consideration the nature of the 
soil, which operates unquestionably upon the distribution of 
the insect race, through the medium of those vegetable pro¬ 
ductions upon which the larvae of many of that race are sup¬ 
ported. That the soil of Wales and of Cornwall differs very 
essentially from that of other parts of the island, is apparent 
to the most casual observer, in its stoney and rocky surface, 
no less than in its internal treasures of metals and ores. 
jSIontagu, who had in captivity a little brood of this spe¬ 
cies, observed that the parent Nightingales fed them chiefly 
with green caterpillars, but does not mention of what descrip¬ 
tion these were supposed to be. This is to be regretted, as 
it might have afforded a clue to this curious investigation, 
since we know that many insects, in the caterpillar state, 
confine themselves entirely to one or two species of plant 
for food, and reject all others. 
The conjecture mentioned by the same naturalist, that 
Nightingales may possibly not be found except where cow¬ 
slips grow, agrees with the theory here hazarded, that the 
soil may have great influence on the partial distribution of 
birds. With regard to cowslips, which indicate a particular- 
soil, moist and loamy, we can add our own testimony in 
corroboration of this opinion, that the places which we have 
constantly known to be most frequented by Nightingales are 
well supplied with this fragrant plant. 
But, if the excluded parts of the kingdom are not supplied 
with the food proper for this species, it may be asked, upon 
