THE HAWK MOTH.

Hawera & Normanby Star, Volume XLII, Issue XLII, 13 April 1922, Page 3

THE HAWK MOTH.

WHAT A TONGUE!

A moth very seldom seen in New Zealand, and certainly extremely rare in Wellington, a tobacco hawk moth (sphinx convolvulus), was caught at Lyall Bay last week by Mr. St. George A. Dowsing. This specimen has a tongue nearly five inches long, which, when not in use, it curls up like a watch spring. Realising its rarity Mr. Dowsing handed the moth to the Museum authorities.

In a recent Strand Magazine appears an article on this species of moth, written by Mr. John J. Ward, F.E.S. Mr. "Ward gives interesting photographs of the beautiful Convolvulus Hawk Moth. In one photograph, the moth is shown in the act of extending its remarkable proboscis, or sucking tongue, into the air amidst the flowers. Another photograph shows the tongue coiled un ; jike a watch, spring, and a fourth photograph, illustrates the moth with its tongue tucked away into the lower part of its head. In his article Mr. Ward asks, "Why does the moth need so long a tongue?" and he proceeds to explain: "That is a really wonderful story of evolution, for its proboscis has kept pace with the length of the floral tubes at which the moth seeks refreshment. As the flowers produced longer and longer tubes to protect the nectar at their bases from undesirable insects which did not assist in their effective pollination, so the invited guests (the hawk-moths) extended their tongues more and more to reach the sweet fluid; thus a reciprocal development of the floral tubes and the moths' proboscides was brought about. Look at the next flower of the tobacco plant (Nicotiana affinis) which you see in your garden opening its white petals towards eight o'clock in the evening and emitting its powerful scent, and carefully observe the two inches of the tube between the mouth and base of the flower, and there you have the whole story. The moth follows up the scent until it sees the white petals, :and over 'them, while poised on i£s powerful wings, it uncoils its proboscis and darts the tip of it into the remote depths of the flower in search' of the honey" fluid it contains, and an instant later it rises and withdraws it, only to descend again and plunge it into the next nearest bloom. It can, of course, also sip nectar from shorter tubes, as in the case of those of the honeysuckle; but the tobacco plant has specialised, as it were, on this particular type of insect for its fertilisation—a highly-evolved tactic, for the ex. termination of the insect would probably mean the extinction of the plant also.

"The moth's sucking-tube is not the simple tube it appears to be] it is,, indeed, a most complex piece of mechanism, consisting of a pair of flexible pipes laid side by side and grooved on i oiv inner surface, being interlocked v.\ih minute hairs to form an airtight til-ft through which the floral sweets are absorbed. Should a particle of nonfluid material pass up the tube, the moth can readily separate the two airpipes and so, remove the obstacle. The whole mechanism is a marvellouslyconstructed suction-pump. "As shown in the photographs the tongue can bo quickly, coiled up and put safely away beneath the lower part of the head, and the photographs show clearly the moth changing its position on the branches so as to enable it to clear its proboscis of the stems and leaves while recoiling it. I was also able to make a moving picture film of the moth extending and recoiling its tongue in this manner, and from the amount of film run off I was able to calculate that the uncoiling, waving in the air three or four tirnies. and recoiling occupied about seven' seconds of time.

"The Convolvulus Hawk Moth presents the most interesting British example of a moth with a really long sucking-proboscis, but, in warmer countries, still more wonderful examples occur. Charles Darwin had some flowers of a Madagascar orchid sent to him with whip-like nectaries of eleven and a half inches long, with nectar only in their lower inch and a half, and he ventured the opinion that there must he moths with proboscides between ten and eleven inches in length to" reach that nectar. The suggestion was ridiculed by some entomologists, but, later on, Fritz Muller recorded a moth from South Brazil with a proboscis which (even in the dried specimen) measured between ten and eleven inches and formed a coil of twenty or more windings.

"Some ten kinds of hawk-moths are found in the British Isles, some of which, as the Privet, Lime, and Poplar HawkMoths, are quite common species. The Death's Head is one of rarer kinds, and a migrant like the Convolvulus Hawk Moth, hut. unlike it, is remarkable for its short tongue.