﻿THE CATTLE GEUBS OR OX WARBLES 5 



They have also expressed the opinion that it is not improbable 

 that the larvae may go from the legs to the gullet and thus to the 

 back. Hadwen, working in British Columbia, has also made some 

 valuable contributions to our knowledge of Hypoderma. In a paper 

 published in 1912 (32), he presents data on tlie injuriousness of the 

 cattle grubs in Canada and adds some valuable information on the 

 method of egg laying of H. ho vis. 



The seriousness of injury by cattle grubs in Germany led to the 

 appointment of a commission to study all phases of this subject. 

 Several years were spent in this investigational work and the results 

 were published in parts in the years 1912 to 1919 (67). A large 

 amount of information was obtained on the losses due to the pests, 

 relative numbers of the two species, life histories and habits, and 

 control work. 



C. Stub (95-99) carried on observations on cattle grubs in Den- 

 mark and published his records in 1912, 1913, 1915, and 1919. He 

 added to the information on the life history and habits of the 

 insect and reported that, in collaboration with Prof. Phil Boas, he 

 found beneath a number of eggs a burrow through the skin which 

 they interpreted as the entrance hole of a newly hatched larva. 

 Stub also foimd larvse from 2 to 7 millimeters long in the subclermal 

 connective tissue of calves. In early records, he concluded that the 

 larvae burrow directly through the skin, but was under the erroneous 

 impression that the eggs are laid on the back. In 1919 (99) he 

 definitely traced the course of young larvEe from the inside of the 

 right tibia to the esophagus. 



Hadwen published further observations on the life history and 

 seasonal development of both species in 1915 (33). In this paper he 

 showed that larv^ removed from the gullet and placed under the 

 skin on the leg of calves would work upward rapidly through the 

 connective tissues and ultimately reach the back. In 1916, Hadwen 

 and Bruce (38) attemjoted to trace the larvaj as they left the gullet 

 and suggested that they pass up the crura of the diaphragm or along 

 the posterior borders of the ribs to the neural canal and out through 

 the posterior foramen to the subcutaneous tissues of the back. In 

 another paper (34-), in 1916, Hadwen added further data on the 

 seasonal development of the larvae and demonstrated the ability of 

 the newly hatched larvae to penetrate bovine skin. He also described 

 lesions on cattle chargeable to the penetration of Hypoderma larvae. 

 Later a concise account of the cattle grub problem was issued by 

 Pladwen (30). 



In 1920 Carpenter and Hewitt (18) described in detail a successful 

 experiment with warble eradication on Clai-e Island, Ireland; and in 

 1922 in the sixth report (7.9) on the problem. Carpenter, Pbibbs, and 

 Slattery presented further infoinialioii on the lile :ind seasonal his- 

 tory of both species of Hy])o<l(.'rma and further experimental evi- 

 dence that lai-vai enter the host through the skin only and not by 

 way of the mouth. This report also summarizes tests with various 

 dressings applied to the backs of cattle to kill the grubs, especially 

 tobacco-powder wash. The biologies of Ilypodernui and othei- 

 aspects of the gi-ub pioblem wci'e summari/ecl by Seymour-Jones 

 (91) and Warburton (J 10) in 1922. 



