26 INSECT PHYSIOLOGY 



Respiration of parasites 



The internal parasites of insects, which live a semi-aquatic life within 

 the blood and tissues of their host, naturally show many of the res- 

 piratory adaptations possessed by aquatic larvae. In the young stages 

 of many of them the tracheae do not contain air, and oxygen simply 

 diffuses from the blood of the host into the blood of the parasite - as 

 it does in the young aquatic larva of Chironomus (Dipt.) and Acentro- 

 pus (Lep.), &c. Later, when air has appeared in the tracheae, these 

 commonly supply a rich network of branches to the skin - as they do 

 in the older aquatic larvae of Simulium, Chironomus, &c. There are 

 often outgrowths from the body surface, usually from the tail, which 

 recall the gill-like organs of aquatic forms. Sometimes these struc- 

 tures are well supplied with tracheae (as in the larva of Cryptochaetum 

 (Agromyzidae : Dipt.) ) or with circulating blood (as in Apanteles 

 (Braconidae: Hym.) ) and are of proved importance in respiration; 

 but in most cases their respiratory significance is very doubtful and 

 their function is problematical. Finally, the metapneustic type of 

 respiration common in aquatic insects is seen in most Dipterous 

 parasites (Tachinidae, &c), which pierce the body-wall or the large 

 tracheal trunks and breathe the atmospheric air. The habit of attach- 

 ing themselves to the tracheal tubes recalls the fact that certain 

 aquatic larvae (of the beetle Donatio, and the mosquito Mansonid) 

 possess specially modified respiratory siphons which they insert into 

 the air-containing tissues of aquatic plants, and are thus able to 

 remain permanently beneath the water surface. 

 The role of haemoglobin in insect respiration is discussed on p. 36. 



BIBLIOGRAPHY 



miller, P. l. Physiology oflnsecta III (Morris Rockstein, Ed.), Academic 

 Press, New York, 1964, 558-617 (insect respiration) 



Thorpe, w. h. Biol. Rev., 25, (1950), 344-390 (plastron respiration: review) 



wiGGLESWORTH, v. b. Biol. Rev., 6, (1931) 181-220 (insect respiration: 

 historical review) 



The Principles of Insect Physiology, 6th Ed. Methuen, London, 1965, 



317-368 (insect respiration) 



