OBSERVATIONS ON THE BIOLOGY OF SAWFLIES. 229 



q non - „ Total laid per r ,. ., , 



bpecies. insect. Individual rate of laying. 



P. pavida . 57 . None in 4 days ; 6 after 1 da 



51, laid in about 10 hours, 

 after 5 days. 

 P. luricliventns . Spec. 1 : 7 egg-holes in 4 days 



.-2:3' „ 5 ,; 



s (In green stalk of leaf, egg laid in 



1/ 3-5 minutes.) 



Promptitude in Laying and Relation to Feeding. 



In all the succeeding cases, except where otherwise stated, 

 the flies were obtained a few hours at most after emerging and 

 then given opportunity to feed on sugar syrup. 



A. serotinus. — A single specimen laid after 7 days. 



Allantns pallipes, and Pristiphora pallipes. — Both these laid 

 immediately after hatching and feeding. They also laid normal 

 eggs in the normal fashion without feeding. In these latter 

 experiments moisture in the form of condensation on the glass 

 cage was available but whether it was taken or not was not 

 observed. 



N. fuscipennis. — In two experiments the flies were kept fast- 

 ing with their host plant, alder, for 4 and 5 days respectively. 

 Neither laid. But immediately after a feed of sugar syrup both 

 commenced laying. 



N. luteus. — One specimen produced eggs one day after 

 emerging and feeding, but another, despite frequent meals, never 

 laid. 



P. obductus. — One specimen laid almost immediately after 

 emergence and feeding while a second delayed for about a day. 



Explanation of the complete failure to hatch of th*e eggs of 

 Nematinus luteus and Pteronidea pavida I am unable to offer. 



4/ 



Emergence of Adults. 



Premature emergence. — In three instances this phenomenon 

 has been observed. About the end of May, 1921, a caterpillar of 

 Allantus serotinus, a non-spinner, went to ground in a litter of 

 peat, sand and coconut fibre. On June 4th it was placed in a 

 small corked bottle under about fin. of litter. Three month- 

 later, September 2nd, a green male pupa was found on the 

 surface, where it remained on its back for 16 days when it became 

 active. Two other specimens did not emerge from litter till 

 ready for adult life. 



The second case concerned Pteronidea pavida, which went 

 into the litter to spin about July 15th. The cocoons were kept 

 under conditions similar to the above. A month later, August 

 15th, a light green male pupa appeared on the Burface and lay 

 there for 8 days before becoming active. Five other specimens 

 behaved normally. 



