HELIOTROPISM 
545 
of Lilac (Syringa persica), appeared to be quite indifferent to the sun’s 
direction. The fourth was at first settled facing the sun, but it very- 
soon moved, settled again, and at once adjusted its position so as to 
be perfectly oriented with tail to the sun. I subsequently watched 
the same butterfly settle three times, the first time with tail turned 
to the sun correctly, but the second and third times it alighted on 
Blue-bells and did not orient itself. 
Vanessa urticae , Linn., was far less common and only two 
specimens offered themselves for observation, of which the first was 
twice seen to adjust itself to correct orientation, but the second, on 
the same Lilac bush with the V. io mentioned above, appeared, like 
it, to be indifferent to the sun’s direction. 
From the preceding observations it may fairly be inferred that 
Vanessa io (and probably also V. urticae) when settled in full sun¬ 
shine, except sometimes when feeding on flowers, habitually places 
itself so that its tail is directed towards the sun. As however the 
butterflies were not seen to close their wings over their backs nothing 
can be said as to the shadow question. 
The next species that came under my notice was Melitaea aurinia , 
Rott., which was very abundant in a restricted North Devon locality. 
All the specimens observed were settled on flowers or low plants; 
in the great majority the wings were fully expanded, though a few 
had the fore-wings drawn back so as to form an approximation 
to the Deltoid shape. In order to secure perfect fairness my method 
was to record the position of every specimen seen so long as the sun 
was shining brightly. Three series of observations were thus made, 
with the following results 
First Second Third Total 
series. series. series. 
Tail to sun . 13 29 69 111 
Side to sun. 2 6 9 17 
Head to sun.1 2 0 3 
Adjustments after settling were often noticed, occasionally 
repeated adjustments. When there was a wind they settled at first 
with their heads to it, one butterfly succeeding in orienting itself only 
after much struggle. When the sun was not shining they were often 
noted settled at right angles to its direction. 
Under the circumstances in which this local butterfly, M. aurinia , 
occurred, it is difficult to see that the amount of shadow thrown 
could have been of any moment, though doubtless its colours 
would show up more if the undersides of the hind-wings when at 
rest had the sun shining directly on them rather than tangentially. 
2 n 
