2G6 



THE AGRICDLTURAL NEWS. 



August 17, 1912. 



INS[CT NOTES. 



THE COTTON WORM IN THE 

 UNITED STATES IN 1911. 



In a recent number of the Ayricultuj-al News (see Vol. 

 X, p, 378) reference was made to a general outbreak of the 

 cotton worm {Alabama argillacea) in the cotton-growing 

 districts of the Tnited States. It was mentioned that 

 Mr. W. D. Hunter, who is in charge of the southern field 

 firop insect investigations of the Bureau of Entomology of the 

 United States Department of Agriculture, was endeavouring 

 to account for the unusual occurrence of this in.sect on the 

 theory that it had invaded the Southern States by migration 

 from Mexico and perhaps also from the West indies. 



At a meeting of the American Association of Economic 

 I'.ntomologists at WashingtDn, D.C , in I lecember last, 

 Mr. Hunter read a paper on the Outbreak of Alabama 

 iirgillaceu in 1911, which has been published in the Journal 

 of Economic Enlomologij, Vol. V, p. 123. The following 

 items are abstracted from Mr. Hunter's paper and the report 

 nf the discussion which followed its reading. 



For nearly a quarter of a century there has been no 

 serious outbreak of the cotton worm in the cotton belt of the 

 United States until 1911, and as a result many planters were 

 not familiar with this insect. The reserve stocks of Paris 

 green and other arsenicals throughout the South had become 

 much reduced, and when the outbreak of the cotton worm 

 became general the demand for arsenicals became very great, 

 many of the larger factories in different parts of the country 

 running night and day. 



The earliest seasonal record for this insect in 1911 was 

 received from Brownsville, Texas, which is on the Mexican 

 border, and at two near-by points in Mexico. As early as 

 June 10, the greater number of cotton fields in this district 

 were almost entirely stripped of their foliage. In Louisiana 

 and Mississippi, defoliation of cotton fields began to be 

 reported about the middle of July. In the eastern part of the 

 cotton belt, thi.s condition was observed in August and 

 September. 



It is concluded that the outbreak of 191 1 started from two 

 infestations, one apparently unimportant, in the eastern part of 

 the cotton belt, another of greater importance in southern 

 Texas, which began in Mexico, but it does not seem that the 

 occurrence of the cotton worm throughout the cotton belt 

 could be e.^plained on the theory that these two infestations 

 Lad spread and eventually coalesced. At widely separated 

 points extending far to the north of the latitude in which 

 this insect breeds, large swarms of cotton moths appeared 

 almost simultaneously between September 19 and October 

 29. It is stated that the occurrence of these enorraoua 

 numbers of moths toward the end of the season and the 

 rapid increase cf the caterpillar shortly before that time were 

 due to invasion of moths from South America through 

 Mexico or over the Gulf of Mexico. 



Rather complete and full records exist of the depreda- 

 tions of the cotton worm from 1793 to 1881. These 

 contrast strongly with the meagre accounts of this insect in 

 more recent years, when bj- the use of arsenical insecticides 

 and changed plantation methods the effects of cotton worm 

 attacks have been mucii modified. 



In 1840 the theory was advanced that severe attacks of the 



cotton worm occurred once in twenty- one years. The records 



-how that in the years 1783, 1804, 1825, 1846, 18G8, 1890, 



lid 1911 there have been severe and general outbreaks of 



Ihi.s insect, while in other years the attacks have often been 



severe in localities but not general throughout the cotton 

 belt, with the exception of one that occurred in 1872-3. 

 Two of the periods indicated by the figures given are of 

 twentj'-two years while the others, it will be observed, are of 

 twenty-one years each. 



Another point of interest which was brought out in the 

 discussion of Mr. Hunter's paper had to do with the food 

 plant of the cotton worm, and its native home. So far as is 

 known at the present time, the only food plant of the cotton 

 worm is cotton, and it is not believed that this insect can 

 live and go through its developmental ch.mges to maturity 

 on any other plant. It is known that the native home of 

 the cotton worm is somewhere south of the United States, 

 probably South America, and it seems to be the opinion 

 among those entomologists who have studied the subject 

 that this insect is incapable of passing the winter in the 

 United States. In that case it is necessary that an invasion 

 of moths should take place each year before any caterpillars- 

 can appear in the cotton fields 



This being so, may it not happen that the severe out- 

 lireaks of cotton worm in the Lesser Antilles follow invasion 

 of the moths from South America.' 



These invasions are probalily not from the same sources- 

 as those in the United States which cause the first attacks 

 there, since in these islands the cotton worm is seldom if ever 

 to be seen in the field in numbers before the last week in 

 September. This date would, however, coincide closely with 

 that at which the great flights of moths were recorded in 1911. 



If, on the other hand, the severe outbreaks of cotton 

 worm in these islands, in certain years, are to be accounted 

 for by inva.sionsof moth.=, it is diflicult to understand why the 

 island of St. Vincent should have escaped and not have 

 experienced a single attack during the past ten years, when 

 in the Orenadines, St. Lucia, and Barbados there have been, 

 during this time, several seasons in which this pest has been 

 present in enormous numbers. 



A Weevil Enemy ofCaravonica Cotton. — Ac- 

 cording to the E'perimeyxt Station Record (Vol. XXVI, No. 4, 

 March 1912) a weevil has attacked Caravonica cotton in 

 Morogoro, German East Africa. The habits of this weevil 

 and the injury caused by it are similar to those caused in the 

 United States by the Mexican cotton boll weevil {Anthono- 

 mus graiidis). 



The description of this pest, which appeared in Pflon- 

 2cr, 7 (1911) No. 514, p. 18, was by H. Morstatt. 



Caterpillars Eating the Grass of Lawns. — 



Mr. J. C. Moore, Agricultural Superintendent, St. Lucia, in. 

 a letter to the Imperial Commissioner of Agriculture, states^- 

 that caterpillars have done considerable damage by feeding 

 upon the grass of the lawns at the Botanic Gardens. Speci- 

 mens of the caterpillars, and of the moths bred from them, 

 have been forwarded for identification. 



Mr. Moore finds that a spray of Paris green in water 

 kills the caterpillars, and does not burn the grass much. 



This insect is similar to, if not identical with, a small 

 moth of the family Pyralidae, reported by Mr. Patterson as^ 

 doing similar damage at the Agricultural School in St. Vin- 

 cent. 



In St. Vincent, the grass-eating caterpillars were exten- 

 sively parasitized by S/nlochalcis femoratus. 



