IN THE BRITISH ISLANDS. 7 



a. var. xanthoceros, Hb. This variety has the anterior wings, with a 

 dark green band like the type, but with a pale ochreous basal line, or- 

 bicular and reniform pale ochreous, outlined in darker ; the pale 

 transverse lines beyond the reniform are also ochreous. Hind wings 

 grey with an ochreous tinge, base paler, and a pale line parallel to hind 

 margin. Most of our banded forms have the pale marks ochreous and 

 would thus belong to this variety. 



/3. var. erythrocephala, Esp. The diagnosis of Esper's variety 

 is : " Noctua spirilinguis cristata alis superioribus fuscis, albo nigroque 

 nebulosis, maculis duabus disci rufescentibus, (feminse albidis)" ( ' Die 

 Schmet.,' p. 309). Esper figures (PI. 128, figs, 1, 2 & 3) the larva 

 with the imago so that there is no doubt about the determination. 



y. var. interrupta, mihi. This is the variety with the central 

 band broken. The base is pale, the dark, central, transverse 

 band on the anterior wings is broken up by a pale patch extending 

 through it from the costa to the inner margin, the dark band being 

 represented by two dark lines on either side of this pale patch. I have 

 specimens of var. interrupta from all localities whence I have obtained 

 the type. When the pale transverse markings are ochreous, I would 

 add-ocArea to the varietal name, when white, alba to distinguish 

 them. 



2. Family: Bryophilidce, Gn. 



This small family is subject to a great deal of variation, and its 

 species are, practically, polymorphic. The polymorphism of this 

 species is a striking illustration of the effect of environment on the 

 colour of the species. They are almost all lichen-feeding species, and 

 the colour of the imagines agrees most perfectly, in many instances, 

 with the lichens on which they feed ; thus, in certain localities, 

 dependent on the character of the lichens, we find certain forms of the 

 imago prevalent, perla var. flavescens is almost the only form obtainable 

 on certain walls in certain districts, although in the same districts, on 

 different walls, the other varieties are common ; so it is with var. 

 suffusa, with var. pallida of the same species, and the various varieties 

 of muralis. This peculiarity extends to the varieties of the other 

 species, algce, &c. on the Continent. The different forms of variation 

 are always in the direction of the extension or suppression of some or 

 other of the typical coloration present, although under certain 

 conditions, coloured scales which are not normally present, are 

 developed to an extraordinary degree, as for example in perla var. 

 flavescens. A difference of intensity in the colour and development 

 of the typical markings also accounts for some of the most noticeable 

 forms of variation. We have only two common British species, both 

 of which are remarkably inconstant, while one reputed British species 

 algce is as variable on the Continent, as are our own species here. 



BryopMla, Tr., perla, F. 



The ordinary pale- grey form of this species, variegated with 

 transverse lines, usually found in the South of England, is the type of 

 this species. The description of Fabricius is : " Noctua cristata alis 

 deflexis cinereis riigro undatis : maculis duabus fuscis." " Alas 



