50 Mr Brindley, Further Notes on the Food Plants 



Further Notes on the Food Plants of the Common Earwig (For- 

 ficula aiiricularia). By H. H. Brindley, M.A., St John's College. 



[Read 8 March 1920.] 



In a paper pubHshed in the Proceedings of the Cambridge Philo- 

 sophical Society, xix, Part 4, July 1918, p. 170, I recorded certain 

 observations in August and September, 1917, on the food plants of 

 the Common Earwig, with the view of obtaining more exact infor- 

 mation than was then available as to the damage likely to be 

 done by this species in a flower or kitchen garden. The paper also 

 epitomised recent literature on the subject, a consideration of 

 which had revealed a considerable amount of diversity and want 

 of exact information as to the favourite food plants of earmgs in 

 the British Isles. The observations made by myself were on earwigs 

 kept in captivity in connection with a statistical enquiry as to the 

 variation of the forcipes which is still in progress. The observations 

 in 1917 were on earwigs from St Mary's, Isles of Scilly, and those 

 recorded in the present paper were made in the second half of the 

 year 1918 on a collection from the Bass Rock, which swarms with 

 earwigs. The animals were all adults and were kept in large glass 

 dishes bedded with sand slightly damped occasionally. Earwigs re- 

 main healthy in a soaked substratum if the ventilation is good, but 

 in captivity in a warm room without circulation of air they suffer 

 heavy mortality from fungoid attack, as I have already recorded 

 {Proc. Camb. Phil. Soc, xvii, Part 4, Feb. 1914, pp. 335-338). The 

 fungus appears to be usually Entomofhthora forflculae (Picard, 

 BuU. Soc. Etude Vidg. Zool. Agric. Bordeaux, Jan.-Apr., 1914, 

 pp. 25, 37, 62). The importance of ventilation and of normal tem- 

 perature is well illustrated by the far fewer fungoid attacks and 

 the low mortality when the new Insect House belonging to the 

 Cambridge Zoological Laboratory became available in 1919. It is 

 at present too early to say how far an improvement is obtainable 

 in the survival of eggs and young which it is hoped to rear in the 

 spring in normal outside temperatures in the Insect House. Earwigs 

 offer a great contrast to cockroaches as regards desire for water; 

 the latter thrive in captivity for months in ^ warm room on food 

 which is entirely dry, while earwigs certainly visit water to drink, 

 as I have seen in both the captive and wild conditions. I have 

 previously recorded {Proc. Zool. Soc. Lond., Nov. 1897, p. 913) 

 how Stylofyga orientalis in captivity seems to pay no attention to 

 a damp sponge when that is the only source of moisture. We have 

 however to bear in mind that the Common Cockroach is probably an 



