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THE AGRICULTURAL NEWS. 



October ii, 19U. 



INSECT NOTES. 



A NEW COTTON PEST. 



An unusual occurrence has taken place at .St. Kitts 

 during the present cotton-growing season, which seems to 

 indicate that a new and unexpected jiest of young cotton 

 plants has appeared. 



The circumstances of thi.s occuri-ence are briefly stated 

 herewith. 



On two estates in St. Kitts much trouble was experi- 

 enced in getting cotton established in certain fields, the 

 young plants being eaten off as soon as they appeared above 

 ground. On one estate about 30 acres had suffered from 

 these attacks; one field of 14 acres was planted several times, 

 and completely destroyed each time; and eventually another 

 crop was planted instead of cotton. On another estate 

 a patch of about 2 acres in a large field was planited and 

 eaten down .«ix times. 



The characteristic feature of these attacks is to be found 

 in the fact that the cotyledons or seed leaves are eaten. Any 

 plant which gets through the seed leaf stage and develops 

 its first foliage leaf seems to escape further attack. 



The cause of this injury has been difficult to locate, but 

 after repeated searches the Agricultural Superintendent has 

 established the fact that the damage is done by cockroaches. 



At the time of the Mycologists's visit to St. Kitts in 

 July these affected cotton fields were visited by that officer 

 with Mr. Shepherd, when they found a few crickets, grass- 

 hoppers and cockroaches, but no beetle-grulis or cut worms 

 were found which might have caused the injury. 



'Sh. Shepherd afterwards applied a piiison bait of corn- 

 meal and Paris green to a portion of this field planted with 

 cotton for this purpose. Four days later the plants were just 

 coming up, and they were unliiirmed: but there were large 

 numbers of dead cockroaches lying on the ground in the 

 vicinity of the rows where the poison had been applied. 



Since that time the Agricultural Superintendent has 

 conducted experiments with similar cockroaches collected in 

 the fields where the cotton has been attacked; and these 

 in.sects in captivity have destroyed the young cotton in 

 a manner exactly similar to that in which the young plants 

 were destroyed in the field. 



The cockroach concerned in these attacks on cotton 

 has been identified as the Australian cockroach (Periplaneta 

 australasiae). This is the common household cockroach in 

 the West Indies. The insects so far observed in the field have 

 all, or nearly all, been the young or immature stages of this 

 species. 



This attack on cotton by cockroaches is very unexpected, 

 for although several species of these insects are known to 

 occur in these islands they have not before been suspected of 

 being serious pests of field crops. Their association with the 

 injury under consideration lends a new interest to them, and 

 it is hoped that whenever cockroaches are observed in the 

 fields by planters and others, they will be coDected and 

 forwarded to the Agricultural Officer in each island, with 

 a statement of the conditions under which they occur, and 

 remarks as to the kind and extent of injury whir-h they are 

 supposed to cause. 



TRI-TRI IN ST. LUCIA. 



An interesting note on the habits of these little fish 

 appeared in the West Indian Bulletir-, \'n\. XIV, No. 1, 

 based on the observations made by ilr. W. X. Sands in 

 regard to St. Vincent. It will be remembered by those who 

 read this article that the tri-tri is able to ascend an almost 

 perpendicular surface provided it is covered with a film of 

 moisture. In tliis way the fish are enabled to migrate up 

 the rapids so tyiiical of West Indian streams. 



The economic side of the habits of these fish is brought 

 out in a letter recently received from .Mr. A. Brooks, Acting 

 Agricultural Su[)erintendent, St. Lucia. In this it is 

 recorded that the tri-tri have invaded the hydraulic ram at 

 the Reunion Kxperinieut Station to such an extent that 

 the water service was temporarily put out of action. 

 It seems that the .fjsh travelled about |^ mile up the 

 C'hdiseul River, then along a stone canal and climbed a 

 perpendicular stone wall 15 feet high over which the 

 waste water flowed from the I'am. Thoy continued on 

 through a small hole in the wall and entered the house 

 containing the ram. They then passed through the double 

 valves, the ram which was working at full pressure all 

 the time, and entered the air chamber and w-ere then 

 forced up the delivery j)ipe tri a height of a little <)ver 

 200 feet. Arriving there they gave ;i great deal of trouble 

 by blocking the hose nozzle. 



A few days later the ram stopped and it was foimd to 

 be entirely choked with tri-tri, aucl the chamber of the air 

 cock on the plateau 200 feet above, when opened, were found 

 to be full of these fish, still living in a condition of consider- 

 able activity. 



To prevent any further invasion of this kind a wire 

 screen has been placed in a suitable position to render the 

 recurrence of such an event impossible. 



Telegony. — .\ very interesting article im thesuliject of 

 telegony (the supposed influence of impregnation upon subse- 

 quent conceptions) appears in the Journal of Htreditp for Sep- 

 tember 1914. In this article, as in the previous one noted in 

 the Arjriculturnl, Neio.t, it is shown that there is no direct 

 influence. The circvimstance has to be borne in mind, 

 however, that a female which produces a second ottspring i.s 

 no longer the female that produced the first offspring; in 

 other words, the conditions of environment of the second 

 foetus are difi'erent from those of the first. But the e.ssential 

 fact is that the female has no means of 'warehousing' in any 

 way the characters belonging to the first male. It is known 

 of course, by way of example, that during the development of 

 the foetus the functions of the mother's jiancreas cease to 

 operate, the two (jrganisms being entirely- dependent upon 

 the pancreas of the foetus. This indicates a complete inter- 

 mixture of blood, but investigations have shown that the 

 blood of the mother returns to its normal composition 

 immediately aftei' birth. Similarly the functions of the 

 pancreas become normal again as shown by the composition 

 of the blood as regards its sugar content. From these 

 considerations it will be obvious that what is generally 

 considered telegony has nothing to do with heredity, and 

 should not lie introduced into discussions on points which 

 concern the transmission of characters. 



