32 



suctorial sac, but variations of pressure of air in the sur- 

 rounding tracheal plexus, enlarging or contracting them, 

 and being in the confined space of the insect's head, com- 

 pelling the sac to contract or enlarge compensatorily. The 

 force for doing this is probably chiefly derived from the 

 action of the abdominal muscles on the abdominal air sacs 

 seen in the specimens shown, assisted by reaction that is 

 probably chiefly the result of the elasticity of the tracheal 

 vessels and other parts. That the alimentary canal is also 

 inflated appeared to be the case in transparent-bodied 

 Tipulae observed at emergence, there being a large cavity 

 containing both air and fluid, of which the latter was voided 

 on completion of the expansion of wings and contraction of 

 the abdominal proportions. The tension so obtained was 

 no doubt also useful in wing expansion, etc. 



Several members remarked that the}^ had heard the 

 larvae " squeak." 



Mr. Step said that the gurnard fish possessed an internal 

 air-bladder which was constricted in the middle, and by 

 means of pressing the air through this constriction it 

 produced a grunting sound. The fishermen had named it 

 the " Piper." 



APRIL 2Sth, 1901. 



Mr. H. S. Fremlin, F.E.S., President, in the Chair. 



The evening was devoted to a special lecture by Mr. R. 

 Kearton on " Wild Life in Nature." This was illustrated 

 by many pictures on the screen from his own photographs. 



MAY gth, 1901. 



Mr. H. S. Kremlin, F.E.S., President, in the Chair. 



Mr. Step exhibited a number of living specimens of a 

 Coleopteron, Mycetophagns qnadripiistnlntns, taken on the banks 

 of the Brent in decaying fungi. 



Mr. S. W. Kemp exhibited a box containing seventy- 

 eight cases made by larvae of caddis-flies (Trichoptera) of the 

 genera Phryganea, Limnophilns, Sericostouia, Anaholia, and 

 Molanna. They were all found either near London or at 

 Oxford. 



The larva of Limnophilns pellncidus cuts circular pieces 



