Kank — Oil Ii'ish Lepidojjfcra. 107 



and nocturnal, do not fly in an easterly wind, whicli is the only one 

 ■which could carry off English specimens perforce across the Irish Sea, 

 and you at once limit the list to those which voluntarily undertake 

 the transit, an impossibility to the Lithosiidse and Geometridae, which 

 constitute very nearly two-thii'ds of our Macro -Icpidoptera. 



That occasional visitants from France, such as Lycsena bcetica, Pa- 

 pilio podalirius, and Catephia alchymista, have been taken on the south 

 coast of England cannot be denied. But a south, or south-westerly 

 wind, which is one favourable to their activity, would bring them 

 across the Channel. Yet we do not find that the English south coast 

 receives any permanent accessions of species fi'om such arrivals. 

 Many hardy insects, such as Vanessa levana, abound in the north of 

 France, which have never been recorded in Britain. 



The genus Dianthoecia is another group of swift-flying insects, 

 though smaller in size than the Sphingidae. Of this whole genus 

 Great Britain possesses only eight species, four of which have not 

 crossed the Irish Sea ; out of which two are scarce and local 

 in the south of England ; but of the other two, one is generally 

 common, and the other abundant, in Somersetshire and elsewhere. 

 But Ireland also reckons seven species, three of which are not 

 found in England or Scotland. Of these, the first, D. barrettii, is 

 peculiar to the Hill of Howth, though now considered to be a remark- 

 able variety of D. luteago, a species which occurs rarely in Central 

 Europe. 



The second, D. compta, has been taken three or four times in Ire- 

 land, and is fairly abundant in France. The thii'd, D. csesia, an 

 insect found in some mountain districts on the Continent, has been 

 hitherto taken in the Isle of Man, and one specimen at Tramore, by 

 Mr. Warren Wright, many years ago. D. capsophila has been looked 

 on as having its head quarters at Howth, although it is also a Manx 

 insect, and two specimens have been taken at Pembroke, in Wales. 



One object I proposed to myself this summer was the further in- 

 vestigation of this group. The occurrence of D. barrettii only in one 

 very restricted locality at Howth, while its food-plant flourishes luxu- 

 riantly everywhere on the littoral, seemed a remarkable anomaly. I 

 was successful in taking it on the coast of Waterforcl, and, I believe, 

 the larvse on the Wicklow shores, but unfortunately an accident killed 

 the pupae before they hatched out. I have no doubt that the insect 

 occurs elsewhere, but its habits are such as to render it very difficult 

 to capture. The divergence of this insect fi'om its original type is so 

 great as to lead to the inference that a vast period must have elapsed 

 since its isolation from the parent stock. 



D. luteago occurs very rarely in Mecklenburg, Pomerauia, and 

 elsewhere in Central Europe, in Sardinia, Corsica, and it is one of the 

 rarest French moths. 



The other two Irish species, D. csesia, and D. capsophila, present a 

 puzzle in their geographical distribution. On the Continent the latter 

 is found in Spain, Corsica, S. France, and Switzerland, but never 



i:. T. A. PROC, SEE. II. VOL. IV. — SCIKXCE. U 



