Destructive action of the Teredo navalis. 151 



and I observed that the wings of the young ones began to appear. The 

 head still retained the dark-red colour, but the black lines on the body 

 had become much fainter. 



Again, on the 31st, large flights continued to pass, driven by the wind 

 to the southward ; of course very few alighted. They caused little mis* 

 chief within our view. The wings of the young tribe (the whole four 

 being now formed) were about one-eighth of an inch in length. After this 

 time, I made no particular observations on their progress, being otherwise 

 engaged ; but they disappeared in a few days. 



2. Destructive action of the Teredo navalis on vessels built of Teak Timber* 

 By Mr C. Wilcox. 



The following interesting observations on the oeconomy of the Teredo 

 navalis is taken from the Report of the Portsmouth and Portsea Philoso- 

 phical Society. They form the report of a lecture by Mr C. Wilcox. 



" The habits and economy of the Teredo navalis, the most destructive of 

 the testacea, were described, and the irregular shape of the shell, descrip- 

 tion of the head, and formation of the hinge and valves noticed. A fine 

 specimen was exhibited, and the statement of authors who affirm that it 

 extends the whole length of the tube proved to be erroneous ; since these 

 tubes, which are formed by a peculiar secretion from the body of the ani- 

 mal, are often many feet in length and circuitous in their course. This 

 was shown to be the fact, by a large piece of wood pierced in all directions. 

 The manner in which it effects its passage, and the appearance of the 

 interior of the tubes were described. The assertion that the Teredo does 

 not attack teak timber was shown to be incorrect, and its destructive ra- 

 vages on the bottom of ships exemplified, by a relation of the providential 

 escape of His Majesty's ship Sceptre, which, having lost some copper from off 

 her bows, the timbers were pierced through to such an extent as to ren- 

 der her incapable of pursuing her voyage without repair. The lecturer 

 then exhibited the formation of the tubes (through an extent of several 

 feet) in a plank of African timber. Hence the opinion, that the Teredo is 

 attached to one end of the shelly tube was considered to be erroneous, as 

 in this case it would have exceeded seven feet in length. The opinion 

 that the animal revolved was also presumed to be unfounded, for then 

 only one valve (from the peculiar construction of the head) would be ef- 

 fective ; whereas by a seraivolution both are called into action ; while, 

 from its very tender state, and the contorted direction of the tubes, it must 

 of necessity be twisted up, if such revolutions took place. Mr Wilcox then 

 noticed the habits and economy of the Pholades, exhibiting some specimens 

 both in the living and dead state. Their manner of boring was explained, 

 their phosphorescence shown, and their ravages described. The lecturer 

 next adverted to an insect called the Lepisma, and concluding by stating 

 that these minute depredators were frequently so numerous, that 300 will 

 occasionally be found in the space of two inches Square, and their attack 

 commences the moment the timber is in the water, more particularly in 

 the eastern part of the globe. 



