Insects, 6899 



employing lliera with vigour his position is reversed in mid-air, and he descends to the 

 earlh, vainly endeavouring to change it or arrest his fall ; or he dashes himself with 

 violence against some obstacle, thus bringing his flight to a sudden conclusion. The 

 power to hover has been completely lost. After a few eflforts of this kind it becomes 

 almost impossible to compel a mutilated specimen to attempt flight. It will remain 

 fixed in one place for two or three days, and at the end of that time may make 

 a voluntary effort to use its wings. The irregularity, not to say the madness of its 

 flight, is no less observiible than in the beginning. Under these circumstances one of 

 my specimens escaped into the open air from my study in day-light. After extricating 

 himself from amongst the branches of a tree standing near the door, he arose into the 

 air in a spiral track, around which he ascended until attaining a height at which he 

 was almost lost to sight. Here he maintained himself by sailing on his wings, until 

 I lost sight of him by intervening houses. But though I placed myself quickly in a 

 position to see him again, he was nowhere visible, and must have descended suddenly 

 from mid-air. The males of the same species, taken by what is called pairing, in full 

 possession of all their powers and instincts, and animated especially by the sexual 

 instinct, are strongly attracted by light. If the light in a room be so guarded that the 

 specimen cannot injure itself, and a perfect male be held by the thumb and fingers 

 beneath the wings and thrown with force in a direct line from the light, the individual, 

 by the use of the wings, will arrest himself as the force of the impulsion diminishes, 

 and, reversing his position in the air, will return to the light in a direct line. This 

 may be repeated any number of times, and will be followed invariably by the same 

 result. Let the antennae of the specimen then be excised in successive portions. The 

 excision of the upper third does not diminish the power to arrest itself and to return 

 again iu a direct line ; but, beyond this jioint, flight begins to be impaired without 

 effecting in any manner the desire to return, until at last we reach a point where it 

 becomes evident that the voluntary direction of flight is no longer under the volition 

 of the insect, or that some co-ordinating influence is wanting, having special relation 

 to the direction of flight, or the uses of the muscles of the alary organs. Instead of 

 being capable of arresting itself and returning in a direct path, the insect now darts 

 from the point of arrest to the right or left, to the ceiling or the floor ; and this uncer- 

 tainty of direction and inability to arrest the force of impulsion continues to increase 

 until we reach the neighbourhood of the bulb, when the voluntary employment of the 

 wings almost ceases. All these results are obtained simply by the excision of the 

 pectinations of the antennee, leaving the antennal stalks uninjured. The desire 

 to fly is not affected in the first place, and it is only after the individual ascertains 

 the uncertain nature of his efforts that he fixes himself in a state of rest. The 

 structure of the organs, together with these experiments, entirely justify the inference 

 that the antennae, instead of being organs of any special sense, as they are usually 

 regarded, are, in Lepidoptera, instruments of atmospheric palpation, having especial 

 reference to the action and use of the wings in flight. This conclusion has been 

 reached contrary to my own preconceived ideas of the functions of those instruments ; 

 and I believe the view here taken is eniirely new. Should the experiments be 

 repeated by any observer, he should be careful to select for experimental study those 

 le]>idopterous insects that are unprovided with simple eyes or ocelli on the vertex at 

 the base of the antennae. In those species with ocelli on the vertex flight is deranged 

 scarcely at all, as compared with the effect of antennal excision on individuals unpro- 

 vided with these organs. — Dr. Clemens, in tlie '• Journal oj the Academy of Natural 

 Sciences,' Philadelphia. 



