J. Rennie 121 



season caged larvae kept short of food were found in February to 

 measure from 20 to 30 mm. Generally, there has been found out of 

 doors great variation in the size of larvae at the end of winter in the 

 same district and even upon tlie same field. 



Tipula paludosa has been kept under direct observation throughout 

 its whole life cycle, and owing to variations in the length of the larval 

 stage pupation and consequently hatching of adults is spread over a 

 considerable period, viz., in this district, June to September. (Rarely, 

 I have found adults in the cages in May.) Under experimental con- 

 ditions of limited food supplies larvae have been kept alive and been 

 continuously under observation for fifteen months. The minimum 

 duration of the larval period has been found to be about nine months — 

 September to June. Before all the larvae of a season have pupated 

 the next season's larvae may have appeared, so that there may be 

 larvae present in the soil all the year round. There is a possibility that 

 this fact may have led to the view that there are two generations of 

 flies in the year. I have had under observation in breeding cages in 

 the month of July, larvae, pupae, and adults of one generation, together 

 with developing eggs and emerged larvae of the next generation — all 

 alive at the same time; and in the variable climate of the region under 

 observation such occurrences are not improbable in the field. 



Bionomics of the Larva. 



The newly emerged larvae are very susceptible to drought, and 

 when kept in dry soil were found to die off quickly. Strong sunlight, 

 even when the soil is moist, was also fatal in a short time. Artificially 

 reared larvae require to be kept moist and sheltered from direct 

 sunlight, otherwise the mortality in the early days is very great. 

 Larvae which are hatched from eggs which have been placed upon the 

 surface of the ground immediately burrow into the soil, avoiding the 

 light. A large proportion of larvae reared from eggs in 1913 died in 

 the course of the first eight weeks, especially towards the end of this 

 period, notwithstanding all attempts to reproduce natural conditions, 

 and only a comparatively limited number of flies have been reared 

 from many thousands of eggs laid in the laboratory cages. 



In view of the fact that very large numbers of eggs are laid, and of the 

 probability that the adults only rarely approximate to these numbers, 

 there must be a considerable mortality in the course of the life-history, 

 due, of course, to various factors. Our experience suggests that the first 



