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E. M. CAMPBELL-0N INSTINCT. 
pass into the light of day. It is quite probable that some of them 
regard the light of a lighthouse as an exit from darkness through 
which they attempt to fly. B. T. Lowne, who has kept small birds, 
tells me that if at all wild when let loose in a room, they will either 
dash against the window or, on a dull day, fly straight into a bright 
fire. They appear to me to consider light as a road to freedom. 
With the view of seeing how insects with habits not exclusively 
diurnal would regard a flame, I made the following experiment. I 
caught a few humming-bird moths, and released them in a room at 
night in which a lamp was burning. They all flew towards the 
light, and dashed repeatedly against the glass. Now these moths 
fly in' the brightest sunshine, and in the two twilights. I found 
the same experiment lead to the same result in the cases of Gamma 
moths and daddy-long-legs, which are active by day as well as by 
night. The large white butterfly will fly towards the lamp if 
flushed during its usual night’s torpor. All these insects appear to 
me to have committed the same error as birds when striking a 
lighthouse or rushing into a fire. 
This hypothesis obviously cannot extend to similar actions of 
Lepidoptera of nocturnal habits, and I am disposed to think that 
these insects fly towards a flame mistaking it for a flower. The 
objection that a flower visited by moths has scent, and that a flame 
has not, is removed by the fact that bees, which are guided by both 
the senses of smell and sight, will visit artificial flowers. They 
will also walk over a flower from which the corolla is removed in 
such a way that the nectar remains. This would account for 
the attraction of a moth to flame, but its persistent attempts to 
enter the flame appear to be largely due to the following physio¬ 
logical cause. The refulgence observable in the eyes of some of the 
nocturnal Lepidoptera fades away quickly on exposure to brilliant 
light, and reappears only after a considerable time has been passed 
in comparative darkness. Lowne * states that this refulgence is 
due to a luminous reflex from the contents of the rhabdia or rods of 
the eyes, and that its disappearance is owing to the contraction of 
a ring of pigment-cells on the outer end of each rhabdon or rod. 
Now, if the rays of light are prevented from reaching the reflecting 
contents of the rhabdia, they cannot pass to the retina. The moth 
under these conditions is either blind, or can only receive a visual 
impression similar to the undefined glimmer which we ourselves 
perceive when we turn with closed eyelids to a lamp. If the flame 
be such that the moth receives no luminous sensation, it is as likely 
to fly into the flame or bob against the ceiling as to go in any other 
direction. If on the other hand the flame be brilliant, and the 
luminous sensation received by the moth from the direct rays 
approximate to that of the degree of light in which it is usually 
active, the moth would continually seek the flame. 
I have still to refer to the question why animals which fly into 
flame do not fly towards the moon. Were they to do so, and the 
* “On tlie compound vision and the morphology of the eye in Insects.’— 
‘ Trans. Linn. Soc.,’ 2nd ser., Zool.,, vol. ii, p. 389. 
