H. M. Morris 103 



The Tracheal System^. 



From each spiracle except those on the last segment a single tracheal 

 trunk passes inwards, and on passing through the integument it divides 

 into three branches. One branch at once divides into a number of fine 

 branches while the other branches connect with the spiracles before' and 

 behind, these connectives also giving of? fine branches to the tissues. 



From each of the openings of the last pair of spiracles a single trunk 

 passes inwards, and each one then divides into two branches. 



4. HABITS, FOOD, ETC. 



The larvae of Bihio Johannis were found near the surface of the soil, 

 amongst the roots of the grasses of the pasture. The soil near the surface 

 was very rich in organic matter in all stages of decomposition, as the 

 field had been pasture for a number of years. The soil was a medium 

 loam on the surface, but becoming heavier a few inches down. 



The larvae were usually found at a depth of not more than half an 

 inch below the surface, and some appeared to be actually on the surface 

 of the soil ; they were usually in small colonies, in which the larvae were 

 very close together. 



The larvae fed by working particles of soil and organic matter into 

 the mouth by the rather slow movement of the mandibles. 



From examinations made of the contents of the alimentary canal it 

 appeared that these larvae had been feeding on decaying vegetable 

 matter only, as only such material and inorganic particles were found. 



Several observers record having found the larvae of species of Bibio 

 in cow-dung, horse-dung (8, 15) and in other situations where there has 

 been a very high proportion of decaying vegetable matter, as in garden 

 soil (26) and at the base of decaying tree stumps (19). It appears also that 

 larvae of this genus can feed on the roots of living plants. 



The larvae of Bibio Johannis are moderately active and are able to 

 bury themselves in loose soil fairly quickly, assisted probably by their 

 backwardly directed processes. 



The larvae and pupae, contrary to the experience of Malloch(i5) were 

 not found difficult to rear. They were reared in medium sized glass jars, 

 partially filled with soil, grass, etc., similar to that amongst which the 

 larvae were found, the jars being covered with coarse muslin and the 

 soil kept damp. As it was desired to obtain the fly rather early in the 



^ The spiracles have already been described on pp. 96-98. 



