85 '^^ 



Mr. G. Wailes commmncated the following: — 



Rhododendrons and their Enemies. 



" Mr. Noble's communication, as to the destruction done to his Rhododendrons, 

 reminds me of the doings of the larva of Mamestra Brassicae auiougst miue. Many 

 years ago when the variety was scarce in gardens, these larvae nearly ate up the whole 

 of the young foliage of a plant of Rhododendron caucasicum album in a very few 

 days, and on detecting the mischief I picked off some dozens of them. Since that 

 lime I have occasionally seen marks of their handiwork on the lower leaves of R. pon- 

 ticum, especially where the branches sw.ept the surface of the turf. This year they 

 have flown at nobler game, and made sad havoc in a house which I have devoted to 

 the growing of the Sikhim aud Bhootan species. My collection of these fine plants 

 wants only some liiiee or four to include in it all the introduced species, and consists 

 of more tlian a hundred planls. I mention this to show that the larvse had full choice 

 of food before thein, whilst their attacks have been confined to the following, — glau- 

 cum, baibatum, Maddeni, Hookeri, VVindsori and Jenkinsi, and of these the planls 

 were scattered about in different parts of the house, iniermingled with the oiher sorts. 

 I need hardly add that the mischief was done at night, and evidently by larvae 

 of nearly full growth, as may be seen by the leaves I enclose, and, as I found to be 

 the case, when I managed to capture the offenders. My impression is that a female 

 moth had gained access by the open windows, and had deposited her eggs on some 

 other plants in the house, and I noticed that some young Chinese primroses, &c., had 

 their leaves partially eaten, which I concluded was the work of small slugs, and that 

 it was not till other food failed, or the larvae had acquired a taste for roaming, that 

 they had recourse to the Rhododendrons. I have also observed that the larva of some 

 Torlrix attacks aud twists up the small leaves which terminate the growth of such 

 species as R. Dalhousiae, Edgworthii and formosum, but have not yet succeeded in 

 rearing the species. The damage is very trifling, as they don't appear to meddle with 

 the dormant buds. 



" Another curious circumstance connected with these plants I have noticed as regards 

 the habits of what is termed " the white scale," a species of Aspidiotus. This pest, as 

 is well known to all plant growers, confines its attacks almost exclusively to the under 

 sides of leaves, where it often escapes the vigilance of the gardener. In the case of 

 one of my plants of R. Edgworthii, from a nursery, it had established itself on the upper 

 surface along the midrib, and on the depressed veins caused in this species by the 

 bullate areoles of its beautiful leaves. To this locality it had evidently been driven by 

 the thick tomentum which covers the stems and under sides of the leaves, and so pre- 

 vents its attaching itself to the surface of the leaf itself. Here, unfortunately for its 

 safety, it at once strikes the eye and is readily destroyed. 



" The very young leaves of several of the species have suffered also from the doings 

 of the larvai of one of the Tenthredinidae, 1 think an Alhalia, which in summer 

 attacks almost all plants under glass, and seems a general feeder, eating the leaves 

 half through from the under side. This I will endeavour to rear, notwithslandiug the 

 almost irresistible inclination one naturally feels to be rid of it, and to ascertain what 

 it really is." 



