32 THE entomologist's record. 



latitude further north, yet it has a total of 2,713 day degrees above 

 me^., or, against 2,G10 at Cheadle, nearly 4 per cent more The 

 distribution of these is more important. In winter (November to March) 

 they are : Douglas, 458, Cheadle, 315 or nearly 50 per ceii . m 

 favour of the seaside station. For the rest of the year (April to 

 October) they are: Douglas, 2,255 ;. Cheadle, 2,305, a substantm^ 

 advantage in favour of Cheadle. Animal life might, then be active 

 during winter half as long again at Douglas as at dieadle. There 

 is however, the further disadvantage to Cheadle that it has during 

 the winter 564 day degrees under 42deg. whilst Doug as has only 

 247 Insects must, therefore, be so much more chilled at Cheadle 

 as to be unable to make a fair use of their chances. At Cheadle there 

 are fewer warm periods and less power to make use of them, ihere is 

 another factor operating at many of our coast stations, both on the east 

 and west, but especially on our south coasts, viz., the ground has a 

 steep slope facing south either as cliffs or downs and often protected 

 laterally from east and west winds by projecting downs, rocks, or head- 

 lands This is, no doubt, most frequently the case on steep rocky 

 shores where sundry nooks-small, no doubt, in extent-of ten have quite 

 a summer climate for short periods during the winter. Though such 

 places must intensify the effect of the general conditions, and must be 

 taken into account, I have no figures to show numerically what they 

 amount to, neither have I any definite information as to how far such 

 favoured spots retain species that would otherwise perish nor do i 

 know to what extent the habitats, at the northern limits of species on 

 the Continent, may be more or less such favoured spots, bo that witn- 

 out forgetting that such intensifiers of the general effect exist we niust 

 draw our conclusions from such averages as are available, ihe difler- 

 ence of climate making the south coast warmer by about 2deg. than 

 inland would, no doubt, enable some insects to live there that would 

 not "survive inland. The further difference making the winter much 

 milder is probably a more potent circumstance in mamtaining;^certain 

 species on the coast, so that it requires further examination Broadly, 

 the point is that the winter temperature of the coast is such as not to 

 reouire the quiescence of hibernation that obtains inland. 



I may first, however, note how these south coast temperatures 



compare with Continental temperatures. To make this more evident 



to the eye as well as the ear, I have roughly marked on an outline map 



of Europe three isotherms. The winter temperature of the south coast 



is about 42deg. This isotherm crosses the south-west of Ireland, runs 



along our south coast, crosses to France east of the Channel Islands, , 



runs southwards, and, bending eastward in the south of France, runs 



east throuf^h North Italy. The summer isotherm of 60deg. , which also 



runs near the south coast, instead of trending south after leaving us, 



runs north-east along the coast of Holland, through Denmark, takes a. 



great bight northwards to beyond GOdeg. N., into Scandinavia, and 



returning to the southern shore of the Baltic, follows it north-east to 



the neighbourhood of St. Petersburg. The mean annual temperature 



■of 50deg., which corresponds very closely with the isotherm of the 



same temperature on about April 25th, runs along our south coast 



passes eastward and slightly southerly, south of Brussels, north of 



Munich, very near Vienna, and thence fairly easterly. Our south 



coast, then, has a mean temperature, corresponding to 3deg. ot latitude 



