1867.] Entomology. 109 



140 feet wide ; a fine promenade, 560 feet long by 50 feet wide, 

 leads to the pier head., which is 310 feet long by 140 feet wide. 

 The pier head has an area of 39,000 feet, and at each end of its four 

 corners is an ornamental tower, two similar edifices adorning the 

 abutments also. 



The Cincinnati Suspension Bridge is rapidly approaching com- 

 pletion. Its total length, including the approaches, will be 2,252 

 ieet; length of main span from centre to centre of the towers, 

 1,057 feet ; length of end spans, 281 feet ; width of bridge in the 

 clear, 36 feet ; and height above low water, 100 feet. It is sup- 

 ported by two cables of 12-J inches diameter, made up of 7 strands, 

 each of which contains 740 wires. The floor beams are of wrought 

 iron ; two iron trusses, 10 feet high, will separate the footways from 

 the carriageways, and an ornamental iron railing will protect the 

 foot passengers on either side. Wrought-iron girders, 30 feet long 

 and 12 inches wide, will run the entire length under the middle of 

 the bridge. 



7. ENTOMOLOGY. 



(Including the Proceedings of the Entomological Society.) 



In 1863 the Linnean Society published the first part of a memoir 

 by Sir John Lubbock, " On the Development of Chloeon dimidi- 

 atum." The second and concluding part of that memoir has 

 just appeared in the twenty-fifth volume of the Society's ' Trans- 

 actions,' p. 477. It is generally believed that all insects, with few 

 exceptions, pass through three definite stages of existence after 

 leaving the egg ; but in the case of Chloeon there are no such 

 stages ; instead we have a series of gradations. It is true that the 

 Epnenieridae, the family to which Chloeon belongs, have been long 

 known to have their metamorphoses incomplete, but we are indebted 

 to Sir J. Lubbock for a definite account of their various changes. 

 The condition in which the young Chloeon leaves the egg is un- 

 certain, but the smallest specimens being only 18-800ths of an inch 

 in length, and quite colourless and transparent, it is assumed that 

 these are in their " first state." From this point there are not less 

 than twenty states (or moultings), through which the insect pro- 

 gresses before it leaves the water, in which it has hitherto passed 

 its life, to assume the " proimago " form, and this differs apparently 

 from the perfect insect chiefly in certain peculiarities of the wings 

 and legs. It is quite impossible here to follow the various changes 

 which are minutely detailed in the two memoirs ; we can only observe 

 that it is not until the eighteenth stage, that the external sexual 

 characters of the males begin to show themselves, and that in some 

 of the stages a sort of retrograde movement takes place. 



