3( 



^ME TROPtCAL AGFJeULTURlSfa 



[l^EB. I, iBBy. 



ing on the former. Signer Lo Bianco spent several 

 dftys on one of the boats for the purpose of inquiring 

 into this and other scientific matters. Few men possess 

 a keener eye for such sides of nature, or have enjoyed 

 80 good an opportunity of training and regulaiing 

 it as his connexion with the Zoological station at 

 Naples has afforded him. In his opinion the original 

 bank was submerged by volcanic action, and the mud 

 killed the mature polyps. The germs and larval forms, 

 which still existed in the water, settled upon such 

 branches of dead coral as still rose above the sedi- 

 ment, and so began life anew. If he is right, the 

 Sciacca is a kind of submarine Herculaneum. There 

 is not likely to be any immediate improvement in the 

 coral trade. As soon as prices rise, the large tirms 

 will be tempted to sell a part at least of the stock 

 they have hitherto reserved in the hope of better 

 times. If he depression lasts, they may be compelled 

 to do so, which would lead to a further fall. This 

 can have but a small interest for the general public, 

 but the sight of the boats whose crew.s sail or row 

 for long distances without the aid of a compass, guided 

 only by the stars or the glimpse of some distant 

 headland, and in their fishing employ instruments 

 which are said to have been hardly modified since the 

 days of the first Roman Emperors, may suggest a 

 summer afternoon reverie. — Saivrday Eevicw. 



ANOTHER INSECT SCOURGE. 

 The following has been addressed to the editor of 



The A rgics : — 



Sir,^-1 desire to call attention to a species of coccus 

 known as dorthesia. This destructive pest was first 

 observed in the island of Bourbon. Thence it spread to 

 Mauritius, about 25 years since. In Mauritius it de- 

 stroyed the orange and lemon trees, many of tht 

 ortamental shrubs and acacias, and wrecked most of 

 the beautiful plantations and shrubberies. At Port 

 Louis it still exists in loathsome masses on the hand- 

 some Talipot palms. 



About 12 years ago in was noticed for the first 

 time in the Botanical-gardens, Cape Town, and most 

 probably arrived there from Mauritius with piants 

 sent to the Botanical-gardens. During the first sum- 

 mer it spread about three miles into the suburbs alung 

 the railway. Its fearfully destructive character now 

 became evident, for the orange trees, the Australian 

 wattles, the pittc sporums, and the blackwoods became 

 loaded with this disgusting parasite, and the trees 

 slowly but surely succumbed to its attacks. 



Its vast powers of ii crease and its peculiar struc- 

 ture rendered all attempts to check its progress unavail- 

 ing. The adult female dorthesia is about one-third 

 of an inch long, and is fm'uished with a pair of white 

 fluttd wings, similar in form to those of the cicada. 

 Underneath these wings the body appears to be one 

 mass of ova, comprising hundreds of individuals. Syr- 

 inging, &c. , failed to reach this ova, and although the 

 adult dorthesia was sometimes reached and killed, the 

 young escaped, and they are so light that a breeze 

 scatters thtm far and wide. 



All trees of the orange kind, such as lemon, citron, 

 ehaddock, &c., proved especially suitable food for the 

 dorthesia, and once a tree became infested no amount of 

 syringing or washing prevented its destruction. The 

 disastrous results of its arrival at the Cape are all too 

 evident. 



Formerly in Cape Town itself, and throughout 

 the suburbs, the orange tree lent a charm to the gardens 

 that no other tree could give, and in the Westetn 

 Province orange-growing form a most important source 

 of wealth, many farmers netting several liundreds a 

 year from their orange groves. Some of these groves, 

 planted by the Huguenots and their descendants, wtre 

 of great age, and besides being profitable, were objects 

 of great beauty. Those of the Pearl, French Hock, 

 and Wagenmaker's Valley were especially famous. 



To-day this is all changed, and except for a few 

 dead stumps these fragrant groves and this valuable 

 asset in the country's wealth have disappeared. 



Not 80 the dorthesia ; it is still advancing steadily, 

 aud leaving deetructioa in its wake, and will continue 



to do so as long as suitable food is within reach. 

 This plague appears to enjoy a wide range of food, 

 for I have seen medlars, pear trees, oaks, quinces, 

 and many other trees smothered with it. It crowds 

 the stems and leaf-ribs of the pittosporum, the wattles^ 

 the Cape plumbago, aud the pomegranate. Strawberry 

 plants become so covered that the fruit cannot be 

 eaten. French beans and many vegetables also suffer 

 from its ravages, besides roses and many garden flowers, 

 Vines are slightly affected. 



Now, sir, thi« dorthesia has appeared in Melbourne. 

 Yesterday, at Mr. Guilfoyle's request, I accompanied 

 him to the Customhouse, and indentified the coccus 

 covering the two pittosporums at the entrance as 

 dorthesia. I wrote some weeks ago to the Agricul- 

 tural department, urging that every precaution should 

 be taken to prevent its introduction, as there was 

 great risk of its being brought from Mauritius. 



As it is already here, and it has proved so des- 

 tructive elsewhere, I think it the duty of the autho- 

 rities and of the public to use the most strenuous 

 efforts to cope with it before the advent of warm 

 weather. Every jjarticle of vegetation affected by this 

 scourge should be destroyed by burning. It i.s also 

 desirable that a short bill should be introduced to 

 deal with this and similar noxious insects that may 

 reach these shores. 



The shrubs of Melbourne are beautified by trees 

 and shrubs that are particularly liable to attack, and 

 the total extermination of the orange, pittosporum, wattle, 

 and other trees is certain to ensue in a very short 

 period, unless the dorthesia is stamped out. 

 —I am, &c. E. J. DUNN. 



Referring to Mr. Dunn's letter Mr. A. N. Pearson, 

 the Government agricultural chemist, who has had 

 much experience as an entomologist, writes ; — 



" Some cuttings of the pittosporum trees in front 

 of the Custom-house were shown to me about a 

 month ago by a gentleman who was experimenting 

 with some fluid which he hoped would kill certain 

 insects thbt were found on the plant, and I was asked 

 by the secretary of agriculture to state whether or 

 not the insects were dead. I had not previously 

 seen these insects. They were, however, of the coccus 

 family and from the description given in Mr. Dunn's 

 letter I should say they were the dorthtsia he 

 speaks of. There se^i^ms to be some mistake, how- 

 ever, in Jlr. Dunn's description. The mature fe- 

 ma es of all the coccidaj, so far as I know, are 

 wiufiless; the males have wings similar to those of 

 the cicadas (the insects commonly called locusts) ; 

 but in Victoria the body of the female becomes a 

 mass of eggs in nearly all cases, little remaining of 

 the original icsfct beyond a mere shell or skin covering 

 the eggs beneath. In the dorthesia known in Eng- 

 land, however, the mother does not become so com- 

 pletely absorbed into her offspring as is case with 

 most of the other members of the family. All members 

 of the family of the cocciilse which are likely to vifit 

 the shores of Australia may, with very little risk of 

 error, be set down as noxious and warranting imme- 

 diate destruction, even at the cost of some-what drastic 

 measures. All who have anything to do with orchards 

 know what a pest the scale iusect^s; and many in- 

 sects commonly called " blights " are members of the 

 coccus family. I have not heard of this particular 

 dorthesia before ; but species of dorthesia are known 

 in England, and one member of the coccidae family, 

 if I remember rightly, was the cause of the destruction 

 some years ago of all the orange trees in one of 

 the Azores, «here the growth of oranges was the 

 main occupation of the inhabitants. The surest way 

 of destroying these insects is to burn the branches 

 on which they are found, and I learnt this evening 

 that the two pitto-.sporum trees in front of the cus- 

 tom-house, on which these insects had been found, 

 were saturated with kerosene aud compleleiy burnt, 

 so that unless the dorthesia has spread from those 

 two trees it no longer exists in Melbourne. The in- 

 sect which was .shown to me was boat-shaped, varying 

 in size from a micrcscopic object to one-third of a a 

 iucb io length; dirty grey on (b9 back, red uud^r 



