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THE TROPICAL AGRICULTURIST. 



[December i, 1884. 



cheap and effectual insecticide in the shape of water, and 

 a nice shower from the engine or syringe, combined with 

 occasional watering at the roots, will do wonders for roses, 

 for insects, generally speaking, hate water; it is deadly to 

 them. But there is amatterof special interestand importance 

 in connection with the use of water. It is that hot water 

 is more deadly to insects than cold water, and all kinds 

 of plants may be sprinkled or dipped in hot water without 

 injury, provided only it is not too hoj}. You may, by using 

 a trusty thermometer, make a safe rule, and use the water 

 at from 120 deg. to 140 deg. of Fahrenheit, and with this 

 simple agent you may deal out death to the vermin and 

 life to the plants — a very curious example of killing two 

 birds with one stone. In practising this plan, a few care- 

 ful trials should be made. Trust not your hand to know 

 how hot the water is, for you may make a mistake and 

 hold us responsible for the consequences. Provide a bucket 

 of hot water and stir it well about, and by adding hot or 

 cold bring it to 120 deg. Then take a few pot plants, such 

 as fairy roses, primulas, &c, and dip them head downwards, 

 so as to wash the leaves, and move them up aud down 

 a few times, aud then set them aside, to drain. They 

 will be none the worse for it, and the green fly wiil be 

 completely washed from them. — Amateur Gardening. 



THE RAVAGES OF GRUB. 



From the Right Hon. the Earl of Derby to His Excel- 

 lency the Hon. A. H. Gordon, G.O.M.G. 

 Oeylon. 

 No. 297. Downing Street, 6th Oct, 1884. 



Sie, — With reference to my despatch No. 22a of the 15th 

 of July, I have the honour to transmit to you a copy of a 

 further letter from Mr. Thiselton Dyer, enclosing a copy of 

 a report made to the Government of Bengal on the insect, 

 the ravages of which have been mischievous in the coffee 

 plantations of Ceylon. I am, &c, 



Derby. 



Enclosure. 

 Kew Gardens to Colonial Office. 



Royal Gardens, Kew, 23rd Sept. 1884. 



Sir, — Referring to my letter of July 1st last, transmitt- 

 ing to you a report by R. McLachlan, Esq., F.R.S., on the 

 ravages of •' grub " in the coffee plantations in Ceylon, and 

 calling attention to a similar visitation which bad completely 

 devastated the public garden at Darjeeling, I am now desired 

 by Sir Joseph Hooker to transmit to you, for the further 

 information of the Ceylon Government, the accompanying 

 cpoy of a report to the Government of Bengal on the insect 

 which appears to have done the mischief in India. 



For a copy of this valuable document Sir Joseph Hooker 

 is indebted to Dr. King, the Superintendent of the Calcutta 

 Botanic Garden, who - is now in this country. It has been 

 drawn up by Dr. Anderson, F.R.S., the well-knowu Indian 

 Zoologist, and Sir Joseph Hooker believes that, taken in 

 conjunction with Mr. McLaehlan's report already in your 

 hands, it practically exhausts the information attainable on 

 insect ravages of this type. 



I am, &c, 

 W. T. Thiselton Dyer. 



Sub-Enclosure. 



Erom the Honorary Secretary, Zoological Gardens, to 

 C. W. Bolton, Esq., C.S., Under-Secretary to the Govern- 

 ment of Bengal. 

 No. 398. Zoological Gardens, Alipore, 28th Oct., 1883. 



sjm, — I have the honour to inform you that on the receipt 

 of your No. '»>» F., dated the 9th May last, I forwarded 

 specimens of the cockchafer in question in all its stages to the 

 British Museum for identification, as stated in paragraph 6 

 of Dr. King's letter dated the 28th May, 1883. 



Since then I have been anxiously waiting for the inform- 

 ation for which I asked, but T. regret to say that I have re- 

 ceived no reply as yet. I have, however, sent Dr. Gunther 

 a reminder on the subject. 



With regard to the information called for in your letter 

 under reply, I would first point out that all my knowledge 

 regarding the history of this pest at Darjeeling is derived 

 from the reports forwarded to Government by Mr. A. T 

 Jaffrey and by Dr. King, and I have no personal acquaint- 

 ance with the ravages committed by the cockchafer. 



First, as to the probability of any danger to the plants 



resulting from these grubs. Dr. King's experience recorded 

 in his letter is an illustration of the danger that may arise 

 from sending out plants from the soil of a locality, such 

 as the Public Garden at Darjeeling, impregnated with eggs 

 and larva? of this beetle. Tea plants, as is well-known, 

 have no immunity from the attacks of vegetarian beetles 

 in their two stages of larvae and imago, so that were this 

 cockchafer accidentally introduced into a tea garden, it 

 would in all likelihood attack the tea bushes in the same 

 way as it does shrubs and vegetables of the most diverse 

 characters aud properties. In Europe, allied cockchafers 

 also seem to know no limit to the variety of their diet. 

 Whenever these insects occur indigenously, there is always 

 the danger of cycles of iucrease occurring among them, 

 during which they occasionally destroy nearly the entire 

 vegetable life of a district. These cycles are again followed 

 by periods in which the numbers become immensely re- 

 duced, and the pests practically disappear. This has been 

 the experiemce in Europe and A merica. These periods of 

 increase are brought about by certain conditions favouring 

 the deposit and rapid hatching of the eggs and the vital- 

 ity of the newly escaped larva?. One of the conditions 

 which has been ascertained to conduce to the spread of 

 the species of the group of Melolonthidre, of which the 

 cockchafer is a member, is the presence of manure or 

 decaying animal refuse, and I have therefore very littte 

 doubt Mr. Jaffrey and Dr. King have rightly explained the 

 cause of the sudden appearance of the beetle in such vast 

 numbers at Darjeeling. As to whether there is any reason 

 to apprehend danger to the tea plants in Sikkim from 

 this pest, I can only say that if the centre of infec- 

 tion is not efficiently removed, danger must be' appre- 

 hended ; as the species if allowed to go on increasing 

 in numbers, even for a limited period, must of necessity ex- 

 tend its range. Every means therefore should be taken 

 to free the soil in the Public Garden from the larva?, 

 and measures should be taken to destroy the insect. In 

 Europe the following methods are pursued for this purpose: — 

 1. Collecting the beetles. This may be done by picking 

 them from the low bushes and by shaking them from the 

 trees in the plantation on to sheets spread underneath as 

 practised in the forests of Germany and France. Smaller 

 trees are shaken by the hand, whilst the beetles may be 

 precipitated from the larger trees by a smart blow with a 

 heavy hammer against the trunk. Trees which stand singly 

 or at the edge of a plantation, and the leaves of which are 

 eaten by the beetles, shelter generally the largest number. 

 The early morning is the best time for collecting the Europ- 

 ean species as they are then most torpid. In the evening 

 and during the night they are in full activity. 2. Collect- 

 ing the larvae. Care should be taken to destroy all grubs 

 found in manure heaps and in manure when it is spread out 

 over gardens. 3. The soil also should be frequently 

 ploughed or dug up, and the larva? should be sought for and 

 destroyed. In nurseries and in vegetable gardens, when 

 the plants are in rows, the grubs generally follow the rows, 

 making their progress by the dead plants above ground, 

 aud in such cases the grubs will generally be found near the 

 plants that last died. 4. All birds feeding ou the perfect 

 insect, such as crows, jays, magpies, &c., should be strictly 

 preserved ; likewise shrews and moles, which feed on the 

 larva?, and also such carnivorous grouud beetles as the 

 Carabidce. 



I may add that the beetle which has done so much damage 

 in the Public Gardens, Darjeeliug, has been determined here 

 as Lachnoster/ta serrata, but this indentification requires to 

 be verified. Little or nothing is known of its life history 

 which will probably be found in its broad outlines to cor- 

 respond to that of its European and American allies, 

 Melolontha vulgaris and Phyllophaga fusca. 



The former M. vulgaris requires three or four years for 

 its complete development from the egg to the death of the 

 perfect insect but Mr. Jaffrey seems to think that the life of 

 the Darjeeling species is limited to a much shorter period. 

 This aspect of the history of this pest requires careful 

 observation. M. Reiset in his investigations on the ravages 

 of M. vulgaris, presented to the Academie des Sciences in 

 1868, found that in France the larva? of that species takes 

 two years to complete its growth to the pupa stage, four- 

 teen months of which are spent in active feeding and ten 

 months in dormant hibernation. The duration of the pupa 

 stage he found to be eight months, and that the adult cock- 

 chafer lived for three years and a-half. 



