7 



Another remedy now much used in California against the red scale (Aspidiotus aurantii), is 

 hydrocyanic acid gas. Professor Riley thus describes the process: — "The cyanide is dissolved by 

 boiling in water for a few minutes, using 1 gallon of water for each 5 pounds of cyanide. To 

 generate the gas, sulphuric acid is caused to flow upon the cyanide solution in a fine stream, causing 

 the gas to be rapidly given off in the form of a whitish fog. The moisture is taken up by passing the 

 gas through sulphuric acid, which by reason of the water taken up becomes diluted, but may still be 

 employed to generate fresh quantities of gas." 



" The gas is confined to the trees under treatment by means of a suitable canvas tent or fumigator, 

 of which a number of styles have been patented. They are constructed so as to be lowered over the 

 tree from above or to inclose it from the sides." It is found that the gas must be dried as above 

 described, as otherwise it is injurious to the foliage of the trees. It is also stated by Mr. Ooquillett 

 that the trees are less liable to injury when fumigated at night, than when treated in the day-time. 

 The apparatus has lately been simplified, so that it is possible for a planter to fumigate his orchard 

 at the rate of 30 to 40 trees a night. The ordinary commercial fused potassium cyanide is used in 

 the manufacture of the gas, which, it must be remembered, is highly poisonous. 



Very full accounts of the gas treatment, with figures of the apparatus, will be fouud in the 

 Reports of the U. S. Department of Agriculture and other works, which may be consulted in the 

 library of the Institute of Jamaica. If any one resident in the country is desirous of using these 

 remedies, and wishes for more complete details, I shall be happy to give any information in my 

 power ; but the essential features of the remedies are given above, and doubtless the exact method of 

 working and kind of apparatus used would have to depend in each case on the available facilities, the 

 kind of plant attacked, and so forth. 



I shall be greatly obliged to all those who try these remedies, if they will communicate the result 

 to me, so that it may be published for the benefit of the community. The kerosene emulsion has 

 proved very successful on Orange trees near Kingston, but there has been very little experimenting 

 with these remedies in Jamaica 



Natural Enemies. 



Nature has methods for destroying scale-insects which are more effectual than anything which 

 can be accomplished by human means. These consist in other insects, preying upon them, either 

 predaceous in the ordinary way, or infesting them as parasites. They may be grouped as follows;— 



Hymenoptera. 



(1.) Family Chalcididce. — Minute four- winged insects, the larvae or grubs of which are mostly 

 parasitic within the bodies of insects. They can be at once distinguished from the larger Ichneumon 

 flies, by their wings, which, instead of being covered with a network of veins, have the venation 

 extremely reduced, the most conspicuous part being a short vein ending in a knob or stigma, which 

 extends from near the middle of the upper edge of each fore-wing. They are often beautifully 

 metallic green or blue. Mr. L. 0. Howard remarks (Proc. U. S. Nat. Mus., 1891, p. 571.) that 

 hardly a species of scale insect can be found which does not have a formidable parasite among the 

 Chalcididce, of the sub families Aphelininm and Encyrtinoe. These interesting and important little 

 parasites can be reared by keeping the scales in a closed box with a glass top, which admits of their 

 easy observation. When scales are examined with a hand-lens, they may very often be seen 

 perforated by small round holes, where the parasites have escaped ; and in other cases, the parasite will 

 appear as a dark spot or patch within the body of the Coccid. In such cases, by counting the number 

 of infested, and the number of healthy scales, we may estimate the importance of the parasite. 



(2.) Family Mymaridce. — These are similar to the Chalcididae, but still more minute, and Mr. 

 Howard is of the opinion that many, if not most, of those bred from scale-insects are parasitic upon the 

 eggs. Considering the minute size of a Coccid egg, it does indeed seem wonderful that these creatures 

 should be able to undergo their metamorphoses within them ! When we examine a Mymarid under 

 the microscope, the antennas are seen to be somewhat different from those of the Chalcids, and the 

 wings are narrow, especially the hind pair, with very long fringes. A few Proctotrupidoe have also 

 been recorded as bred from scale-insects ; these are very similar to the Mymaridae, but differ in some 

 important structural characters. Many writers class the Mymaridce as a sub-family of Proctotrupidw. 

 Of the Braconidm, which have distinctly veined wings, one species (Lysiphlebus citraphis Ashmead) has 

 been recorded, (Insect Life, Vol. Ill, page 60), as bred from a mealy bug. 



Lepidoptera. 



The caterpillars of some moths live upon Coccidae and their eggs. No instance of this sort is yet 

 known in Jamaica, but several have been recorded in the United States, and in Australia the black 

 scale {Bernardia olecej was observed by Mr. Koebele to be kept well in check by the larva of 

 Thalpochares cocciphaga. 



Neuroptera. 



Lace-wing flies (Chrysopa), easily recognized by their green colour and four finely reticulated 

 wings, have been found to destroy Coccidae in the United States and Australia. These flies, of which 

 one species breeds abundantly on the lignum-vitoe in Kingston, are very delicate and hurmless-looking 

 creatures, but their larvae are extemely voracious, and as they live upon injurious insects, they are 

 very useful. 



CoLEOPTERA. 



The many beetles now recorded as attacking Coccidao belong almost entirely to the family Coccinel* 

 tides, or lady-birds. They are great helps to the gardener, and should bo encouraged in every way ; 

 their appearance is so well known that there is no occasion to describe them. 



