218 



THE AGHICULTUKAL NEWS. 



■Jt-LY 1, 1916. 



INSECT NOTES. 



NATIVE FOOD PLANTS AND FEEDING 



HABITS OF THE COTTON STAINER 



IN ST. VINCENT. 



(Concluded.) 



The following is the concluding part of ihe notes pub- 

 lished in the last issue of the AgiieuUural A'tws de.ling 

 with the native food plants of the cotton stainer in general, 

 and one of them, the silk-fotton tree, in particular. 

 The present notes concern the '.John ItuH" tree (Thespei-ia 

 j>0}iuLnea, Corr.). 



This medium-sized tree is known lucallj- under four 

 vernacular names, these are: '.John Bull', 'AJahoe', 'Gam- 

 boge", 'Bermuda Cedar". It occurs more freciuently along 

 a part of the Windward District which starts at .Stubbs village 

 and extends to Langley Park estate, than in any other part of 

 the island Its numbers are constantly being added to here 

 -owing to the fact that the people use the branches as 'live' 

 posts for fence.s, boundary marks, and wind-breaks. In the 

 Leeward District, and also in the farther portion of the 

 Windward District, the tree has been destroyed to a consider- 

 able extent on account of its haruouring cotton stainers. It 

 produces tiovvers on young shoots. The first flower on 

 a branch opens in February and the last in April, as tar as 

 can be judged at present. About ten flowers are produced 

 on each fruiting shoot of the current season's grovvih. Each 

 Hower gives rise to a fruit which ripens two munihs later. 

 The ripe, leathery, circular, capsular fruit measures 1 1 to 1 1 

 inches in diameter and ^-inch in depth, and contains a number 

 of seeds which are sliahtly larger than those of Sea Island 

 cotton. The seed is thinly covered with a shore downy 

 fuzz. The walls of the young fruit contain a yellow resin- 

 ous liquid, from wliich the tree obtains the name of 

 'Gamboge". The fruit never opens to liberate the seed except 

 by the decay of the leathery covering, and persists on the 

 bianch for a year or more before it drops oil', so that in the 

 month of April there may be no less than twenty fruits, old 

 and young, on each small branch. By the time the young 

 capsules are ripe, the shells of those of ihe ])revious season 

 commence to crack as a result of age, and openings appear 

 usually roiiiidabout the base of the fruit The important 

 point which it is desired to bring out here is that the '.John 

 Jiiiir tree at all times carries a very latge number of .seed 

 re.ssels containing food on which the cotton stainer can live. 



It was mentif)n(;(l in the earlier part of this article that 

 the cotton stainers left the tields about the time the cotton 

 sialks were pulled \x\<. In districts where there were silk - 

 cotton trees they awaicid the boiling of the tiees, as has been 

 described. In districts where theri^ were no silk-cotton tree.s, 

 liut 'John Bull' trees, some of the stainers very (piickly 

 niitde their way to these trees, especially if tliey were close at 

 hand. At the middle of .Xpiil only a few stainers were 

 found away from '.John Bull' tree?, and these were all on a few 

 isolated trees cif the 'Horse Itadish" iveo (Moriiiga ptfiyqos- 

 perma). Here they were feeding on the nectar of the 

 Howers, but were not breeding, and not a single young bug 

 vas observed. All tlie evidence collected, pointed to the 

 fact that it was at the end of February that the insect.-s 

 left the cotton field.s, or about the time tlic cotton stalks 

 were being destroyed. 



In the month of April on every fruiting '.lolin lUill' 

 tree tLere were thousands of insects, both mature and imma- 

 ture, feeding on the old and young fruit. A favourite place 

 ■or tlie young stainers was the old cracked fruit, and at times 



a swarm of them would emerge from such a fruit when 

 opened. The people of the district therefore, state that the 

 'pods breed the stainer bug', and it may be that the mature 

 insects actually lay their eggs in the cracks of the old shells, 

 and the young on hatching out feed on the seed; but eggs so 

 laid have not yet been found. Whereas no insects were 

 seen to be breeding on other plants examined, they were 

 breeding very freely on the '.John Bull' tree, and the conclu- 

 sion arrived at is, that the tree is an even greater menace 

 to the Sea Island cotton industry than the silk-cotton tree, and 

 that botli .>hould be destroyed or systematically prevented 

 from fruiting. 



When it is mentioned that cotton planting was started 

 in April clo.se to a large number of badly infected '.John Bull' 

 trees, it will be realized th-^t unless the tree is destroyed, it 

 will be impo.ssible to prevent the cotton stainer from badly 

 damaging the valuable Sea Island cotton crop. 



An examination was made of the fruit of the ' John 

 Bull' tree attacked by the stainer in order to ascertain, if 

 po.ssible, whether the insect induced a di.sease. No trace 

 of disea.se was found, but there were proliferations of the 

 walls of the fruit and damaged seed. 



There are few natural enemies of the cotton stainer. So 

 far, the chief one observed was the 'l^ipiri' or 'Hawk-beater' 

 (Tyrannus rostr-Uvs). Stomachs of this bird were examined 

 and each was found to contain a large number of these insects. 

 Other birds which prey on the bug to a limited extent are the 

 'Bhick bird' or 'Bequia Sweei' ((JuUodus /uminosas/; the 

 'Tick bird' (Vroiofihaya ani), and domestic fowls. A .small 

 mite, externally parasitic on the stainer, was frequently seen, 

 but appears to be of little importance. A few dead stainers 

 on which live ones were feeding have a'so been noticed, but 

 the cause of death could not be a.scertained. 



As a lesult of the.se investigations, it is suggested that 

 the control of the local cotton stainer will depend primarily 

 on: — 



(a) The destruction of all the old cotton stalks as 

 early as possible after picking is finished in each 

 .season. 



(b) The destruction or pruning back of all fruiting 

 'silk cotton' and '.John Bull' trees. 



These o{)erations c-in be readily carried out. The control 

 of the cotton stainer after it has entered the cotton field is a 

 difficult matter, but it ought to be far easier to .solve this 

 question in the near future, provided the s igges-ions mide 

 are carefuby followed throughout St. Vincent and a close 

 season for cotton, say, from February to .Maj-, is instituted. 



Investigation work on the drugs and poisonous plants 

 of South Africa has been proceeding for some time at the 

 Imperial Institute, and in the current number of the Bulletin 

 of the Bnperial Institute is published a summary of these 

 investiyations as far as completed. The results obtained are 

 interesting and valuable. V'olteno di.sease (a cattle and horse 

 disease prevalent in certain parts of the Union of South 

 Africa,) has been definitely traced to the presence of a poison- 

 ous alkaloid in a plant eaten by the animals. This plant is 

 Srneau lotiioliuf, a near relative of the common groundsel of 

 Great Britain. 'Cape slangkop', a plant belonging to the lily 

 family, which causes cattle poison in the other districts of the 

 Union, contains a poisonous glucoside similar in action to that 

 found in the common foxglove. Among other South African 

 plants of which the properties are still being investigated at 

 the Inijierial Institute are the roots of the 'Ntsema' which 

 are said to be extensively used by the natives employed on 

 the Witwatersrand mines in the preparation of an iutoxicatinsf 

 drink known as 'kali'. 



