president’s address. 
245 
to working this locality, and introduced the large attracting lamps 
which have revolutionised fen collecting. I was fortunate enough 
to take over forty camosa, all males, so that the presence of at 
least that number of females may he inferred, and a fair stock of 
eggs must have been laid. In 1874, however, though the season 
was the best for collecting that 1 ever remember, and I worked 
the Fen regularly on alternate nights throughout July and 
August, I took only four specimens. Eight specimens in all were 
captured in 1875, four in 1870, and five in 1878, since which 
time I have not received complete records of the captures at 
Wickon. It certainly lingered a few seasons after that date. 
I fear, however, that for some years past it has not been taken 
at all. 
The insect is clearly dying out, if not dead. Possibly the 
confinement of the colony to so small a space and consequent close 
inter-breeding was fatal ; but this does not seem to have affected 
others of the local species that inhabit this last remnant of the old 
Fens. I have heard it suggested bv several entomologists that 
the hibernating larvie were drowned off in floods. My own idea is 
just the converse of this, viz., that the increasing dryness of the 
Fen is affecting the food-plant of ctenosa (the Sedge, Cla/Iium 
mariscus , which forms the crop of Wickon) so as to render it 
unsuitable as a pabulum. I am told that the crop now requires 
four years to come to maturity, whereas three years used to be the 
outside allowance. The following facts first suggested to me this 
notion. The winter 1873-74, which appeared disastrous to ervnosa , 
also seriously diminished the numbers of two other species. 
CaUimorpha dominula (the Scarlet Tiger) used to swarm at 
Wicken. On May 7th, 1873, Mr. Fletcher and myself took in 
a few hours a large number of larvte from one patch of Dwarf 
Sallow, and could have secured hundreds more without moving 
many yards — there must have been tens of thousands in the Fen 
(I may state, by parenthesis, that a good supply from our captures 
were turned down at Kanworth, but did not thrive). The next 
year it took me the best part of a day to collect three dozen, and 
it has been scarce ever since. 
