394 



THE AGRICULTURAL NEWS. 



December 13, 1919. 



INSECT NOTES. 



LOCUSTS IN BRITISH GUIANA- 



British Guiana was invaded in I'.UT by an enormous 

 swarm of migratory locusts, which, originating in Venezuela 

 at or near the mouths of the river Orinoco, spread over the 

 entire coastal region of the northwest territor)' as far as the 

 Essequibo River which formed the eastern limit of the migra- 

 tion. A sionlar invasion occurred in 1886 which extended 

 as far as Berbice. An account of the invasion and of the 

 iife-history of the insect appeared in the Bulletin of 

 Entomohgical Research for July 1919 (Vol. IX, p. 341) 

 by G. E. Bodkin, B.A., (Cautab.), Department of Agri- 

 culture, F.Z.S , F.E.S., Government Economic Biologist, 

 and L. D. Cleare, Jnr., F.E.S., Biological Division Depart- 

 ment Science and Agriculture- These notes form a brief 

 review of this article. 



The invasion was reported in July 1917, and by that 

 time the locusts were well distributed. It is believed that 

 the swarm arrived in British Giiima during June. Cassava 

 and maize were the favourite food-plants of the locusts, 

 and inmany places cassava was entirely defoliated, and the 

 corn was destroyed. Other plants suffered from the attacks 

 of the.se insects, but to a much smaller extent- 



The insect concerned in this invasion was probably the 

 game as that identified as SMstocerca paranensis, Burm., 

 which invaded Trinidad a few years ago. There seems to 

 be a great deal of confusion in regard to the name however. 

 The species is variable, and slightly differing forms bava 

 been described undtr different names. The insect is similar 

 in appearance to the common West Indian grasshopper 

 (5. pa/lens, Thunb ). 



After an inspection to determine the extent of the 

 invaded territory and the seriousness of the attack on crops 

 and other plants, an active campaign was started for the 

 control of the locusts. Thi-t campaign, which was con- 

 sidered to have been eminently successful, was conducted 

 over an are^i of 250 square miles, at a cost of ■?2,03S 60 

 (£424 145. 2^-). 



Of all the methods tri^d the use of poisons was the least 

 effective. Other me hods were the destruction of the eggs, 

 burnng, driving into trenches, and the use of molasses and 

 U\- 



With a little experience th2 spots which are attractive 

 to the adult females for egg-laying can be located, and by 

 searching the .soil in these localities enormous numbers of egg- 

 masses can be collected. 



In the drier districts very satisfactory resr.lts were 

 obtained by burning, 'I'he swarms of hoppers were located 

 in the bush, fire started all round, and the swarm destroyed. 



In cultivated areas the hoppers were driven into a mas 

 ol day bush and the bush then fired. The driving of the 

 swarms into trenches proved a simple and eHicacious method. 

 As tlie hoppers arrived in the water in the trenches, kero- 

 sene was thrown in, and the film of oil on the surface of the 

 water hastened the death of the insects. 



Tar or molasses amtarrd on tarpaulins, sheets, palm 

 leaves, banana leaves, flat pieces of tin or other flat surfaces 

 were efficacious in catching large numbers of insects. The 

 smeared materials were spread under clusters of hoppers on 

 the f foliage of plants, and they were shaken off, or the swarm 

 was surrounded by these things, and the hcp^iers driven on 

 to them- 



Practically all the control work was directed to the 

 destruction of the hoppers or immatuie insects. The adults 

 are more difficult to deal with, as they can fly, and egg-layiog 

 had begun before the control campaign was organized. 



It was found necessary to enforce the provision of the 

 Insect Pe^tand Plant Diseases (Prevention) Ordinance of 

 1914, in order to get certain of the farmers to undertake the 

 work of fighting the locusts. When a few examples had 

 been made, no further diihculties of this sort arose. This 

 was the first occasion on which this law had been enforced 

 for the control of an insect pest. 



LIFE-HISTORY. 



Suitable spots are chosen for egg-laying, and here 

 enormous numbers of adult females congregate. The eggs 

 are mo.'tly deposited in the cooler hours of the afternoon. 

 The female forces her abdomen into the soil tunnelling a 

 small excavation by means of the horny processes on the tip 

 of the abdomen. The eggs are voided into the excavation, 

 embedded in and surrounded by a mass of frothy substance, 

 which hardens and becomes somewhat brittle- Each egg-mass 

 contains fifty to sixty eggs which are found at a depth of 

 about 2 i inches. The egg stage occupiei* a peri-)d o' two to 

 three weeks. The newly hatched larvae are a light pea-green in 

 colour, with dull black markings, and they are covered with 

 fine, light-coloured hairs. The antennae are black, the base of 

 each segment i.s yellow, there is a black meso-dorsil line, and 

 the hind femora show three brond black bands 



The first nymphal stage lasts eight days. At the end 

 of eight days the skin is shed, and then the general coloura- 

 tion is much darker, being black with light markings. This 

 stage occupies seven to eight days. In the third nyaiphal 

 stage the general appearance is similar to that of the Sdcond. 

 This period extends from ten to thirteen days. 



Th? lourih stage lasts also ten to thirteen day-, and the 

 appearance of ibeyuuug hopper is m^ich as in the luiid. The 

 wing pads which were first to be seen in the previous stage 

 are now more conspicuous. 



The fifth and sixth nymphal stages are marked by the 

 increasing size of the wing pad<, and the developinu; intensity 

 uf the colour markings. These stages njcispy from nine to 

 eleven, and from fourteen to sixteen days, respectively, 

 making a total length of the cycle from ovipositioi to 

 maturity of tlie insect of from sixty four to t-igh'y days. 

 The length of time from the cha"ge into the adult form to 

 the deposition of tiie eggs is not given, but it would probably 

 add not more than a few days to the figures already stated. 



SUMMARY OF ENTOMOLOGICAL 

 INFORMATION DURING 1919 



For several years past it has been customary to issue a 

 summary of the information relating to entomologicil sub- 

 jects which has appeared in the public.itions of the Imperial 

 Department of Agriculture. This summary has usually 

 been published in the Agricultural Ncwa in the last number 

 or the last tw'> numbers for the year. 



During the year 1919, Insect Notes have appeared in 

 the accustomed place in every number of the Agricultural 

 Nr-.cs. The reports on the Department of Agriculture in 

 the several islands have contained interesting entomological 

 notes, but as the inforn'ation contained in these notes has 

 appeared in another place (Keport on the Prevalence of some 

 pests and diseases in the West Indies during 1917, W'rst 

 hidinn Hullctni, Vol. XMl, Part 2 p. S3) thry will not be 

 Wviewed here. 



