394 OBSERVATIONS ON BIRDS. 
2) 
cating a deadly disorder to cattle. But the truth of the matter is, 
the malady above mentioned is occasioned by the “strus bovis, a 
dipterous insect, which lays its eggs along the chines of kine, where 
the maggots, when hatched, eat their way through the hide of the 
beast into the flesh, and grow to a very large size. I have just 
talked with a man who says he has more than once stripped calves 
who have died of the puckeridge; that the ail or complaint lay 
along the chine, where the flesh was much swelled, and filled with 
purulent matter. Once I myself saw a large rough maggot of this 
sort squeezed out of the back of a cow. 
These maggots in Essex are called wornils. 
The least observation and attention would convince men that 
these birds neither injure the goatherd nor the grazier, but are per- 
fectly harmless, and subsist alone, being night birds, on night 
insects, such as Scaraba@i and Phalene ; and through the month of 
July mostly on the Scarabeus solstitialis, which in many districts 
abounds at that season. Those that we have opened, have always 
had their craws stuffed with large night moths and their eggs, and 
pieces of chaffers : nor does it anywise appear how they can, weak 
and unarmed as they seem, inflict any harm upon kine, unless they 
possess the powers of animal magnetism and can affect them by 
fluttering over them. 
A fern-owl this evening (August 27) showed off in a very unusual 
and entertaining manner, by hawking round and round the circum- 
ference of my great spreading oak for twenty- times following, 
keeping mostly close to the grass, but occasionally glancing up 
amidst the boughs of the tree. This amusing bird was then in pur- 
suit of a brood of some particular phalana belonging to the oak, 
of which there are several sorts ; and exhibited on the occasion a 
command of wing superior, I think, to that of the swallow itself. 
When a person approaches the haunt of fern-owls in an evening, 
they continue flying round the head of the obtruder; and by 
striking their wings together above their backs, in the manner that 
the pigeons called smiters are known to do, make a smart snap ; 
perhaps at that time they are jealous for their young, and their noise 
and gesture are intended by way of menace. 
Fern-owls have attachment to oaks, no doubt on account of food ; 
for the next evening we saw one again several times among the 
boughs of the same tree ; but it did not skim round its stem over 
the grass,as on the evening before. In May these birds tind the 
Scarabeus melolontha on the oak, and the Scarabeus solstitialis at 
