THE CATTLE GRUBS OR OX WARBLES Fh 
mum development in numbers in parts of Germany. They are 
known to be abundant in Switzerland, Denmark, Holland, and the 
British Isles, and probably occur throughout Europe. They are 
abundant throughout the greater part of the United States and 
southern Canada. 
It is very doubful if either species of Hypoderma will ever become 
an established pest in the Tropics or subtropics. Both have been 
repeatedly introduced there with cattle, but there are no records of 
subsequent breeding. It is true, however, that positive information 
is very meager as to the presence of Hypoderma in parts of the 
world other than those in which it is a pest. A. H. Ritchie informs 
the writers that in the West Indies he has never seen the warble 
except in four animals imported from the United States. 
No records are known to the writers of the occurrence of Hypo- 
derma in South America. The genus is replaced in tropical America 
by Dermatobia, and its similar injury to hides leads some to think 
‘Hypoderma is present there. 
Hypoderma is not indigenous to South Africa and apparently has 
never become established through introductions. Lounsbury (62) 
and Hutcheon (47) state that they have no knowledge of the occur- 
rence of either species of Hypoderma in native cattle in the Union 
of South Africa. Lounsbury says in a letter: “Now and then 
warbles are found under the skin of animals imported within a 
matter of months, but I have never heard of any being found in 
_ animals bred in the country or here for a number of years.” 
Howard (46) reports the finding of larve of H. lineatum in 
Mozambique, East Africa, but does not say if from native or im- 
ported cattle. 
James Bequaert has informed the writers that in his extensive work 
in Belgian Congo he has never seen or heard of an authentic case 
of the occurrence of either species of Hypoderma in that country. 
He also directs attention to the statement of Roubaud (85), who has 
‘paid special attention to dipterous parasites of mammals in Belgian 
Congo and French West Africa, that he has never seen Hypoderma 
on cattle in that region. In northern Africa, Hypoderma evidently 
occurs. KE. E. Austen writes that the British Museum contains a 
male of 7. bovis from Algeria near Béne, collected May 5, 1896, by 
A. E. Eaton. Vaney (704) in 1911, states that H. bovis occurs in 
Algeria. Willcocks (1/2), in 1918, says that H. bovis occurs in 
_ Egypt, but whether or not it is a common pest 1s not known. 
In Australia, likewise, neither species seems to have gained a foot- 
hold. Tryon, in 1906 (700), and again in 1912 (101) reported the 
apparent stamping out of a local introduction in the Richmond 
| district. Pound (79) describes the appearance of warbles in im- 
| ported stock and adds, “It is difficult to assign any definite reason 
_ why the cattle grub fly has not become established in Queensland. 
_ Evidently the conditions of environment are unfavorable.” Smit 
| (92) states that H. bovis imported into the Dutch East Indies from 
_ Holland apparently failed to establish itself, as no records in native 
_ cattle have been made. 
__ Regarding the nonoccurrence of Hypoderma in Hawaii, Van 
Dine and Norgaard (108) write: “One and possibily both of the 
bot flies attacking cattle have been brought to Hawai with 1m- 
