75 



OAKS AND THE CATERPILLAR PLAQUE. 



G. W. MASON, 

 Barton-on-Humber. 



I WAS much interested in the article entitled ' Sylvan Vegeta- 

 tion of Fylingdales, N.E. Yorks/ by Mr. J. W. Barry Nat/ * 

 1907, p. 423-31), more particularly that section upon the ' Oaks 

 and the Caterpillar Plague.' Mr. Barry refers to the immense 

 destruction to the leafage of the oak trees caused by the ravages 

 of the Caterpillar of the Oak Leaf Roller Moth [Torfrtx viridana), 

 and writes that ' when the caterpillars are at their height, 

 there is a sound throughout the woods as of a light but con- 

 tinuous shower of rain. This is, of course, from the fall of the 

 excrement.' I have frequently visited the large Pelham's Pillar 

 woods, near Caistor, in Lincolnshire, where the oaks are stripped 

 of their leaves in the manner described by Mr. Barry, and I 

 have often heard early in June a light, pattering sound. I 

 ventured to suggest to Mr. Barry, that the real cause of the 

 sound of the ' light shower of rain ' was the working of count- 

 less jaws of hungry larvae, not only of Tortrix viridana, but of 

 several of the genus Hybernia, together with numerous other 

 larvae. It is well known amongst Lepidopterists that June is 

 one of the great months in the year for tree feeding larvae. I 

 cannot help thinking that the excrement is too small to make 

 an appreciable noise ; and besides, the bulk of the larvae of 

 T. viridana are feeding within spun-up leaves, and most of 

 their excrement remains near them entangled in their silky 

 webs on the leaves. As a breeder of Lepidoptera, I know from 

 experience what a noise can be made by a brood of larvae 

 feeding in a small room. It reminds me, too, of a passage in 

 Figuier's ' Insect World.' The author is dealing with the rear- 

 ing of silkworms, and speaking of the full-fed larvae, he says : 

 * the produce of thirty grammes of eggs, consume in weight as 

 much as four horses, and the noise which their little jaws make 

 resembles that of a very heavy shower of rain.' Of course, the 

 silkworm full grown is a large caterpillar ; but I am inclined to 

 think that the larvae of the several species of Winter Moths 

 have a good deal to do with the noise. Mr. Barry, in 

 writing to me, says that the sound certainly comes from the 

 branches of the trees, and he should not have thought that there 

 were any other larvae on them in relatively appreciable numbers. 



1908 Mar . 



