346 



THE AGRICULTURAL NEWS. 



October 29, 1910. 



INSECT NOTES. 



FROG-HOPPERS IN TRINIDAD. 



Considerable interest attaches at i)resent to the damage 

 inflicted on sugar-cane in Trinidad Tiy insects known as frog- 

 hoppers. These are generally found associated ^Yith a con- 

 dition of the canes known locally as blight. E.'ctensive 

 investigations into the life-history and general habits of these 

 insects have been made recently in Trinidad by Mr. F. W. 

 Urich, Entomologist to the Board of Agriculture. A paper 

 dealing with this subject was published in the Bulletin of the 

 Depmtment oi Agriculture, Trinidad, Vol. IX, p. 15, and an 

 interim report by the same author has been recently issued: 

 the following article is based upon the information contained 

 in these. 



Frog-hoppers belong to the family Cercopidae, of the 

 order Hemiptera, sub-order Homoptera. Three species are 

 known to occur in Trinidad, all members of the genus 

 Tomaspis, of which the most important would appear to be 

 Tovias'pis xiostica, Walker, though another species, probably 

 T. hicincta, is apparently also of fairly general distribu- 

 tion. These insects are related to the scale insects and 

 aphids, and are all found attacking living plants, obtaining 

 their food-supply by sucking the juices, as do the other tj-pes 

 of insects mentioned. 



Frog-hoppers have been known to occur for some time 

 in Trinidad, and several publications on the sulyect have 

 been issued from time to time, particularly in the Proceed- 

 ings of the Agricultural Society of Trinidad and Tobago. 

 Full reference to the.se articles is given in the paper by 

 Mr. Urich mentioned above. In addition to Trinidad, the 

 insect is reported as occurring in Central and northern South 

 America from Mexico, Nicaragua, Costa liica and Demerara, 

 and also probably from British Honduras. Canes which are 

 affected become stunted in growth, and the leaves become 

 spotted and eventually die off. The lower leaves become 

 diseased first, but the upper ones are eventually attacked; 

 and if the insects are numerous, the damage done may be so 

 severe that nothing but the bare cane is left standing. In 

 some instances, when the severity of the insect attack has 

 been reduced by dry weather, the canes may recover to 

 a considerable extent. 



LiKE-HisTOEY. The sggs are deposited in dry cane and 

 grass sheaths near the ground, or they may be found sticking 

 to grass stems, just below the surface of the ground. The 

 egg stage may continue, under favourable circumstances, from 

 twelve to twenty days, the main requisite for hatching being 

 a sufficiency of moisture. If the weather is dry, the eggs may 

 remain dormant for as much as four months. On hatching 

 out, a nymphal stage follows, which lasts for a period of 

 thirty-two to forty-two days. In this stage, the insects are 

 surrounded b}- a covering made up of bubbles of fluid, and 

 this gives rise to their popular name of spittle insects. They 

 attach themselves by means of this froth to the young roots 

 of cane or of various grasses, notably of the Savannah grass 

 of Trinidad, Para grass (Panicum muticnm) and Razor grass 

 (Scleria scindens), as well as of various other grasses, and of 

 some herbaceous plants. They are quite active, and can crawl 

 about, often changing their position several times, in order to 

 obtain a fresh food-supply. During this stage, the insects 

 change their skin four times, the wing pads becoming visible 

 during the third and fourth stages. Just before changing its 

 .skin for the last time, the nymph ascends a grass or cane stalk 



to a height of from 1 foot to 3 feet, and undergoes the final 

 moult in a kind of chamber hollowed in the froth surrounding 

 it. The adult insect of 'J'oinanpis postira is about 8 mm. in 

 length; the head and prothorax are bronze with tawny 

 band.s; the width across the wings varies. On emerging from 

 the spittle chamber, the adults crawl up the stems of grasse.s 

 or cane.s, and secrete' themselves in the axils of the leaves or 

 in the folds of unrolling leaves. They remain in this position 

 until dusk, after which they emerge and crawl out and move 

 about on cane or grass leaves. They may be found 

 feeding at this time, or taking short leaps from leaf to leaf 

 either in search of additional food, or of mates; or they may 

 be found crawling about the ground. They also feed during 

 the day, when secreted in the leaves. As the eggs are laid 

 separately and may take different lengths of time to hatch 

 out, depending upon the moisture supply of the situation 

 in which they are laid, it naturally results that the broods 

 are continuous, and that practically all stages in the life- 

 history may be found at any time during the year, unless 

 the weather is exceptionally dry. The insects can tide over 

 such a period of drought, when in the nymjilial stage, by 

 sheltering under heaps of trash, or on grass growing as 

 a weed on -cane field-s, as well as in crack-s in the soil. 



-METHODS OF CONTROL. Two principal methods have 

 been employed for reducing the numbers of these insects. 

 The first consists in destroying them b}- means of light traps 

 at night. These traps are made of ordinary hurricane lant- 

 erns, standing on bricks in common baking pans tilled with 

 oil and water. Each trap is placed on a small mound of earth 

 about 1 foot high, and several are usually employed in each 

 field, at intervals of about .50 feet. By the use of forty- 

 eight traps of this type, as many as 2.52,5-59 insects were 

 captured on one estate in Trinidad, in one night. The second 

 means of control consists in keeping the fields weeded as 

 cleanly as possible, until the canes are old enough to keep 

 down the weeds for themselves. After the field has been 

 clean weeded and the trash removed, it is found that a careful 

 applicj,tion of a contact insecticide, such as kerosene emulsion 

 produces very good effects, if carefully applied. The mixtures 

 recomn'ended are kerosene emulsion diluted 1 in 10, kero- 

 sene lysol emulsion 6 per cent., and cyanide of potassium 1 oz. 

 to 1 gallon of water. These should be applied by means of 

 a knapsack sprayer. Each stool of cane must be thoroughly 

 drenched, and the spray should also beap[ilied to the ground 

 between the cane rows. The spraying should be repeated at 

 intervals of three weeks. The best time of the j-ear for 

 ajjplying the sprays is immediately after the crop and before 

 the rains commence. It should further be pointed out that 

 all weeds and trash removed from infected fields should be 

 burned or deeply Imried, and that in serious attacks it may 

 even be found advisable to strip the canes completely of all 

 their trash, and to collect this carefully and burn it. 



N.\TUR.\L ENEMIES. The Only natural control of any 

 consequence which has so far been observed is that of 

 a fungoid disease which occurs on both the adults and 

 the nymphs in Trinidad. Some account of the work 

 which has been carried on with this fungus in Trinidad 

 appears elsewhere in this number of the Agricultural 

 Newts, under the heading of Fungus Notes. 



In addition to that in the publications mentioned above, 

 information is given in the Agricultural Neios, Yol. V, p. .3'50, 

 and in the Proceedings of the Agricultural Society of Trini- 

 dad and Tobago, Vol. A'lII, part 9, the latter of which has just 

 come to hand. In this, a paper is given by Dr. Gough, who 

 first discovered the eggs of the frog-hopper, a few days before 

 this was done by Mr. Urich. 



