[ 115] 



which the metal cages containing the larvae were sunk. A consider- 

 able number of larvae wandered from the cages and were subsequently 

 recovered amongst the sand, alive and to all appearances quite healthy. 

 Adult flies were later seen emerging from the cages in the laboratory 

 to which they were removed during July. The larvae of this and 

 Experiment II were collected in the fields and had wintered out of doors. 



The foregoing, together with other experiments and observations of 

 a like nature have shown clearly that the Tipula larva may subsist in 

 the soil and complete its development independent of the presence or 

 absence of a growing crop upon the ground. The results here obtained 

 have led to the institution of further and more exact experiments 

 dealing with the nutrition of soil larvae including Tipula. These are 

 at present in progress. 



IV. A number of larvae caged in the autumn of 1915 were kept 

 in soil without growing vegetation except for a short period when a 

 small quantity of corn sown in the cage germinated. In February 

 they were found to have reached a fair size. Several killed and ex- 

 amined on the 19th were found to contain soil particles and fragments 

 of vegetable fibre. At this date they were found mostly in compact 

 earthen cells formed against the sides at the bottom of the cage. This 

 habit has been frequently observed in winter and suggests a quiescent 

 period under the adverse conditions of cold, confinement and restricted 

 food supply. 



In order to determine more clearly the circumstances inducing 

 destructive attacks upon crops the following type of experiment was 

 resorted to: 



Groups of larvae were put up in large cylindrical glass cages of 

 about 10 inches diameter, in prepared soil, in which the visible amount 

 of vegetable matter was very slight. This soil was, further, mixed 

 with well washed sea sand. Around the cylinders between the glass 

 and the soil, oat seed was introduced. The cages were kept at room 

 temperature and were examined daily. After the corn had germinated, 

 the larvae were kept under close and continuous observation for pro- 

 longed periods at a time. The larvae appeared sluggish, and not much 

 movement was seen in the day time, although their burrows soon 

 became very numerous between the soil and the glass (Plate XX). 

 They could be seen lying in these, and after the com had germinated, 

 or even before this, they could be seen attacking it, gnawing at the 



