68 INSECTS AND MAN 



Were the females blessed with the power of flight, their 

 distribution over large areas would follow, as a matter of 

 course; but, as they are practically confined to the spots 

 where they are born, the question of their travels has been 

 the subject of much experiment. Into the details of all 

 these researches we cannot enter, but one of them, at least, 

 is of special interest ; it concerns the caterpillar in the first 

 stage of its existence, that is to say, before the first moult. 

 In 1893 two Austrian scientists, Wachtl and Kornauth, 

 published the results of some experiments they had carried 

 out regarding the distribution of the first-stage larvae of 

 the nun moth, Psilura monacha, and, at the same time, 

 they described some peculiar hairs to be found on these 

 caterpillars, and stated that similar ones were to be found 

 on first-stage gipsy moth larvae. These hairs only occur 

 on the earlier stages of the caterpillar, and, as they are 

 furnished, near the base, with globular enlargements, 

 which were supposed to be filled with air or gas, they 

 were called aerostatic hairs, and the globules were called 

 aerophores. Experiments conducted in the forests of 

 Austria showed that the nun moth larvae were carried 

 long distances by the wind, and, by analogy, it was assumed 

 that the gipsy moth larvae, being similarly furnished, would 

 be carried like distances. Microscopic examination of a 

 first-stage larva revealed two kinds of hairs, arising from 

 each of the tubercles which are arranged along the body 

 (fig. 13). Of these hairs a few are slender and nearly half 

 as long as the caterpillar, and a considerable number of 

 much shorter ones are furnished with globular swellings 

 near the base. Whether these aerophores actually assist 

 the young larvae in their distribution, by making them 

 more buoyant, is not actually known, but experiments in 

 America show that the larvae can be carried, by the wind, 

 a third of a mile, from a point less than six feet above 

 the ground, and that the most favourable time for the dis- 

 persion is when the temperature is above sixty-five degrees 



