SURVEY OF IXYERTEBBATES 129 



5. PARASITIC ARTHROPODS 



Only a few parasitic arthropods have been studied 

 with respect to their ability to withstand lack of oxygen. 

 The best-known case is that of Gasterophilus intestinalis 

 {= G. eqiii). The larvae of this fly live in the stomach 

 of horses and other animals where they probably en- 

 counter from time to time quite low oxygen tensions 

 (Weinland, 1915). Normally, they are animals with an 

 aerobic metabolism (von Kemnitz, 1916). They have in 

 their abdomen an organ rich in tracheae, the so-called 

 red organ, which consists of very large cells containing 

 haemoglobin ( Prenant, 1900 ; Yaney, 1902 ; von Kemnitz, 

 1916). It seems likely that this organ functions as an 

 oxygen store (Weinland, 1915; Krogh, 1941) that will 

 tide the animals over periods of adverse conditions. 



The Gastcropli'ilus larvae withstand a complete ab- 

 sence of oygen for j^eriods of several days to several 

 weeks as the experiments of Schwab (1858), von Kemnitz 

 (1916), Dinulescu (1932), and Blanchard and Dinulescu 

 (1932) have conclusively demonstrated. It seems that 

 the ability to live anaerobically is well developed in the 

 entire family. Dinulescu {I.e.) found that the larvae of 

 Gasterophilus peeorum, of G. intestinalis and of G. in- 

 ermis survive at 38° C, under anaerobic conditions, for 

 at least 25 days, those of G. liaemorrhoidalis for more 

 than 17 days and finally those of G. nasalis for 17 days. 



Mam?- insects and insect larvae which have the habit of 

 tunnelling in the skin of higher animals and of man will 

 probably also experience some difficulty in getting their 

 normal oxygen supply when no direct communication with 

 the outside world is maintained. The study of the re- 

 sistance of animals leading this type of life has not yet, 

 to the present writer's knowledge, been undertaken on a 

 larger scale. The only form investigated is the larva of 

 Cordylohia antJiropophaga. Its behavior has been stud- 

 ied by Blacklock, Gordon and Fine (1930) who have shown 

 that the animal normally keeps the aperture in the host's 



