NATURAL LOCALITIES OF BRITISH COLEOPTERA. o7 
members of the genus occur on barren heaths or waste places 
that are never touched by the sweeping-net. There is no doubt 
that some rare species may be found in such localities, and 
hence, probably, their rarity, for very few people think of 
sweeping the centre of a barren-looking field. JI remember the 
late Mr. Garneys telling me of a rare species (I think one of the 
Mordellidz) that he took in this way, and brought to London just 
as it was on the point of being erased from the British list. 
Very few collectors have ever tried the twilight before 
sunrise; although many species might then be found, it is 
probable that it would not prove nearly so good a time as the 
twilight after sunset, as in the latter case the ground is heated, 
in the former it is chilled. There is, however, a very productive 
time during which hardly any beetle collectors think of working, 
and that is the night; lepidopterists know well that Carabide, 
Longicorns such as Prionus, Helops ceruleus, Eryx atra, and 
others, come freely to sugar. Opilo mollis owes its rarity 
probably to being, as a rule, a species that comes out at night, 
when it may be taken on elder and other trees. The Carabi are 
always prowling about by night, and on this account are so often 
found crushed in the pathways; it is rather the exception than 
the rule to see a large Carabus abroad in the daytime; actual 
sweeping, however, at night will soon prove how many species are 
abroad. It is a very good plan in many localities to sweep 
promiscuously in the dark with a large deep net, and then tie it 
up tightly, and examine its contents at leisure next day. Mr. 
Matthews and Mr. Crotch on one occasion took Stenus opticus 
(then very rare) in abundance by adopting this plan, although 
they could not find a single specimen during the daytime. One 
of the very few known British specimens of Sesia allantiformis 
was found by Mr. Matthews in his net one morning after sweep- 
ing in this way on the previous night, so that this may be a hint 
to lepidopterists as well, although they are nocturnal workers by 
profession already. 
With regard to weather and temperature a warm day after rain 
is the best; a little moisture is necessary, and a warm damp day, 
with no sun at all, will sometimes bring out such sun-loving 
Species as Longicorns in abundance, and everything else in 
proportion ; dry heat is unfavourable; a south or west wind is 
almost indispensable; a north or east wind is fatal to success in 
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