DIMORPHA VERSICOLORA. 243 



(Chapman). The egg is long, nearly 2mm., somewhat cylindrical in shape, 

 but almost twice as long as broad, the extremities rounded, a distinct 

 longitudinal depression on upper surface of egg ; the colour at 

 first pale yellow*, rapidly becomes dirty yellow and after three days 

 orange-brown, whilst the development of the embryo can be ob- 

 served, certain dark areas being very pronounced ; the colour then 

 gradually changes to purple-brown, and, five days after being laid, the 

 eggs are of a tint roughly corresponding with that of the dead birch 

 twigs (the infertile ones remaining yellow) ; the empty eggshell is 

 glassy, transparent, and distinctly iridescent (Ent. Rec, iv., p. 156). 

 The egg is about 2mm. in length, rather more than imm. wide, in 

 shape much like that of a brick with rounded-off angles, slightly 

 depressed on the upperside, sometimes on both sides, the surface 

 apparently smooth and very glossy ; when first laid, of a light 

 green colour, changing in the course of a few days to dark brownish- 

 purple, much the colour of a fresh birch twig ; this lasts for about 

 fifteen days, and it then assumes a purplish-violet tint, gleaming 

 like an amethyst, and the interior seems a little cloudy ; a few hours 

 later it is fainter and pinkish, and then the larva soon hatches ; the 

 empty shell, with the circular hole of egress at one end, still retains a 

 faint tinge of pinkish-violet after the larva has escaped (Buckler). The 

 eggs when first laid are of a bright yellow colour, but soon assume a rich 

 brown tint, much the colour of the twigs on which they are deposited ; 

 in warm, sunny weather, the change of colour will be effected in 24 hours, 

 but when cold and dull it occupies several days ; in this state the eggs 

 remain about three weeks or a month, varying with the temperature ; 

 the movements of the young larva can be seen within the pellucid 

 shell, and the young larva nibbles a hole at the end of the egg, 

 the majority getting clear in half-an-hour (Gascoyne). The 

 eggs at first bright yellow change gradually to pale purple-brown, 

 becoming brown rather than yellow in three days from laying 

 (Merrifield). Length of egg 2mm., width i'2mm., thickness at 

 larger end imm., at thinner end just under imm. ; in outline, a 

 long, rather brick-shaped oval, flattened on sides and edges, but 

 full and rounded at ends ; a large depression on upper surface, a 

 small one on lower ; colour finally of a livid leaden hue ; surface 

 smooth and varnished. The micropyle forms a dark spot at one 

 end, the surrounding network of cells faintly but clearly marked ; the 

 general surface only with the slightest trace of any reticulation 

 (Bacot). It is essential that the ova should be kept in the shade and 

 not exposed to the full rays of the sun until they begin to hatch 

 (Bernard-Smith). 



Habits of larva. — As soon as the larvae emerge, they con- 

 gregate and feed gregariously, sitting closely together on a twig 

 of the foodplant, clinging by their prolegs and holding the head 

 and thoracic segments away from the twig. When startled, they rapidly 

 throw themselves up, and much resemble Tenthredo larvae, although 

 the latter cling by their true legs and elevate the posterior segments. 



* We are informed that some error seems to have crept into the original here, 

 the egg being noted as first "pale greerj, then yellow," and several observers agree that 

 there can be no doubt that the egg is not green but yellow when laid It is strange, 

 if this be so, that Buckler {Lat-vcu, Sec, hi., p. 61) makes exactly the same error 

 of observation. Is there any vaiiation in the tint of different batches ? 



