f8 



Diacrisia mendica. Its History and its Variation. 



By Robert Adkin, F.E.^.—Read October 2Qth, 1922. 



The geographical distribution of Diacrisia mendica extends over a 

 considerable portion of the Palaearctic region. Commencing in the 

 west, we find it practically throughout Ireland, England and the 

 southern two-thirds of Scotland, thence across Europe, except in the 

 Polar regions and possibly the extreme south-east corner, just 

 touching Asia Minor in the neighbourhood of Mount Olympus, and 

 terminating, so far as we know at present, in Western Siberia at the 

 slopes of the Altai Mountains. 



History. 



The species in its typical form is sufficiently well known to ento- 

 mologists of the present day to need no description here, but to those 

 of a couple of centuries ago it appears to have been one of some 

 difficulty, chiefly on account of the disparity of the two sexes. 



The earliest mention I know of the species dates back to 1702, 

 when Jacob Petiver, in his " Gazophylacii Naturae et Artis," 

 figures at Plate xliv., no. 8, an insect which fairly well represents a 

 female /»t?/if//ra, and his description, "alba semidiaphana, guttulis 

 paucis nigris," well describes this sex; he tells us that he is "obliged 

 to Mr. Antrobus for this rare Gawse Moth," which seems to show 

 that the insect was not very well known in this country at that early 

 date, and that the male had not then been detected. 



John Ray's " Historia Insectorum " was published posthumously 

 in 1710, Ray having died some six years previously. At page 197, 

 An. 97, 6, his description — A moth rather below medium size, wings 

 and body white, a few black spots — clearly indicates the female of this 

 species. Then, at page 200, 7, 8. — A moth rather below medium 

 size, wholly dusky or dull cinereous, forewings broad, short, with 

 three black spots on both — leaves no doubt that the male was also 

 known to him, but it is evident that he was quite unaware that these 

 two moths were the sexes of one species. 



Between the years 1734 and 1742 — Reaumur published his 

 " Memoires pour servir a I'Histoire des Insectes," a fascinating 

 book dealing with insect bionomics and life-histories. In vol. II. 

 at page 60 he mentions some very hairy larvae that he had, and 

 says " the fast walk of which has made us call it the hare." He 



