154 



THE AGKICULTLfRAL NEWS. 



May 10. 1913. 



INSECT NOTES 



ROOT BORERS AND OTHER GRUBS 

 IN WEST INDIAN SOILS. 



The ai'ticle on this ."subject in the last i.^.sue nf tlie Ayri- 

 <-ulit,rid Keics provided usetnl information ri-garding the 

 occurrence of, and damage inHicted lij-, tlie different ."ipecies of 

 hard back beetles in Barbados and St. Kitts. The following 

 notes continue the fubject in regard to the species in 

 Aniigua, Porto Itico and St. \'incent, and contain important 

 infonnation on the habits of the common hard back. 



'I'he blown bard back in Antigua {Lai-hnosterna sp ). 



In Antigua, grubs of hard back beetles have for several 

 years past been suspected of causing injury to sugarcane, and 

 in December and January (191 1-12) serious damage was done 

 to ii Held of onions. In the latter instance the roots and 

 bulbs of the growing onions were eaten to such an extent as 

 to cause the loss of praclically the whole crop on a field of 7 

 acres. 



In the case of the attacks on sugar-cane, the cutting.s 

 used for planting were often injured sutticiently to prevent 

 the growth of the shoots, thus necessitating a considerable 

 amount of replanting or supplying. 



In the older canes, these grubs are suspected of being 

 riioi trimmers and causing damage by destroying the fibrous 

 roots. 



Itecently (Febmary 1913) the Superintendent of Agri- 

 culture for the Leeward Islands has reported an attack of 

 this kind on Indian corn, in Antigua. In tliis in.-;tance the 

 corn was beginning to ripen iis grain, and the injury to the 

 rooH~ resulted in an appearance of tlje plants similar to that 

 observed in plants dying of drought. K.\amination revealed 

 the fact that many of the larger root.s were denuded of tlie 

 finer laterals. Injury of this sort may have been partly 

 responsible for the conditions of Indian com sutt'ering from 

 root disease, at times in Antigua, before the presence of the 

 grubs was as^ociated with the unfavourable condition of 

 Indian corn, but in this instance no root disease symptoms 

 could be discovered on e.\amining the roots. 



The adult of this grub is a brown hard back somewhat 

 smaller than J'/ii/talns smillii, and considerably larger than 

 L'tc/aiostirna })af7-iielis. Specimens were sent for identitica- 

 tioQ to Mr. Guy A. K. Marshall of the Imperial Bureau of 

 Entomology, who states that it is La<-/inostirna sp. and that 

 there are no specimens of it in the British Museum. 



The May lieetle or 'Caculo', in I'orlo llico {Lnc/mos- 

 tetna sp ). lieferences; Annual lieports, Porto Rico Experi- 

 ment Station: Second Annual Report of the Sugar Producers' 

 Association of Porto liico, 1911.12. 



This is another brown hard back, larger in size than any 

 of those already discussed. The following quotation is taken 

 from the report by Mr. I) L A'an 1 >ine, I'lntomologist of the 

 Sugar Producers' Association, included in the Second Annual 

 Report (see reference above). 



'The "May beetle', iMchnaati) im sp. 



'The injury to the roots of the sugar-cane by the white 

 i;rubof the May beetle is the most acute insect problem before 

 the Porto Rican cane planters. Mr. K. A. Schwart;: of the Bureau 

 of Entomology at Washington pronounces the species to be 

 closely allied to L. ueylrcla, Burm. 'I'wo further species of 

 the sub family Melolonthides have been collected from the 

 cane field.", one of which breeds at the roots of cane and the 

 distribution agrees practically with that of the common 

 Lachno.-Nterna, though it occurs in comparatively very small 

 numbers. At least three species of the related subfamily 



Dyanstides have been collected also, and in a certain district- 

 one of these, a large Rhinoceros beetle outranks the common 

 "May beetle" in numbers and in the injury to the cane ' 



The white grub in Portu Rico is a root trimmer, and so 

 serious were the injuries resulting from its attacks that the 

 Sugar Producers' Association mainiained one of its Assistant 

 l'".ntomologists in the United States for a considerable time 

 employed in searching for a parasite or parasites which might 

 exercise a satisfactory control over it in Porto Rico. 



The white grub attacks the roots of orange trees and of 

 several grasses, as well as of sugar-cane. Often as many 

 as fifty grubs have been taken from soil around the base of 

 young orange trees. They sometimes cause the death of the 

 tree. The adult beetle is a leaf feeder. 



Lachnoslerna patenx in St. Vincent. Reference: Agri- 

 enllnral iVtics, Vol. XI, p. 34tj. 



This hard back beetle is considerably larger than any of 

 those already mentioned. Only the adult form is known. 

 In this stuge nf its life it feeds on the leaves of cacao and 

 other plants. 



DYN.VSTII).\K. 



The insects included in this group are mostly scavengers 

 in their mode of feeding in the larval cordition; that is to 

 say, the grubs of the Dynastid beetles generally feed on dead 

 and decaying vegetable matter. 



It is known, however, that they sometimes depart from 

 this habit and become active enemies of growing plants. 

 Examples of this are found in the West Indies, and several 

 species, in which this change of habit is known to have 

 occurred, are referred to below. 



The common hard back {Liiitirus tuinnlosus). Refer- 

 ences: West Indian Bul'etin, Vol. VI, p. 37; Agricultural 

 News, Vols. VII, p 218, and I.\, p 18G 



This is the most widely distributed in the West Indies 

 and probably the most generally known of all the beetles in 

 these islands. 



It is the dark brown or black hard back which occurs 

 in all the islands of the Lesser Antilles and is the one 

 that is attracted to lights in houses, and comes buzzing and • 

 bumping around the Inmps, falling with a thud to the floor 

 or table, and then after a short pause frantically startino- 

 ort" again. 



The larvae live in d>-caying vegetable matter such as . 

 megass, dead leaves, and pen manure. They probably do 

 not attack plant tissues, that is, it is unlikely tliat they 

 feed on roots, under ordinary circumstances at least, 

 although tliey are often found in the soil in which plants 

 are growing. 



It is only recently that the ditl'erence between 

 the larva of this insect and that of the brown hard 

 back {Phytalus smit/ti) has been recognized in Barbados, 

 and it seems likely that confusion may exist in each 

 island as to the distinctions between harmless grubs 

 in the soil and those which injure plants by feeding upon 

 their roots and portions of the underground stem. These two 

 kinds of grubs are similar in their general appearance. The 

 grubs of all hard backs are whitish in colour and are 

 possessed of three pairs of slender legs, which are attached 

 to the thoracic segments — the anteri<ir portion of the body 

 just behind the head. The presence of these three pairs of 

 legs is the chief characteristic which distinguishes the 

 bard back grubs from the root borer or weevil larvae, as 

 these latter are always without legs. 



A related species, Li</i/rus rw/iaps, is known as the 

 sugar cane beetle in the southern L'nited States. It is in 

 the adult condition that this insect is injurious, for it is the 

 adu". which eats out cavities in the underground stem por- 



