42 



THE AGMCULTURAL NEWS. 



January 29, 191G. 



INSECT NOTES. 



DANGEROUS HARD BACKS. 



The subject of hard back grubs in the soil has received 

 consideration in several publications of this Department 

 during the past two or three years. Owing to enquiries 

 recently made at this Office in regard to these insects, the 

 following summary of the present situation has been prepared 

 for the information of West Indian planters. 



REFEEEXijES. Dur- 

 ing the period from 

 March 21 to .June 7, 

 1913, the Insect 

 Notes in six num- 

 bers of the Agri- 

 cultural News (Nos. 

 285 to 290) dealt 

 with root borers and 

 other grubs in West 

 Indian soils, and 

 these articles were 

 reproduced with 

 illustrations as No. 

 7.3 of the Depart- 

 ment's Pamphlet 

 Series. In 19U, 

 Pamphlet No. 75, 

 entitled Sugar-cane 

 Tests of the Leeward 

 Islands, discussed 

 further the occur- 

 rence of these insects, the damage done by them, and the 

 methods of control, or rather of reducing their numbers. Both 

 these pamphlets were fully illustrated. 



In January and February 1914, the Entomologist made 

 a visit to St. Kitts and Antigua, which had for its principal 



Fl: 



1. Ligyrus tuniidosui (about 

 twice natural size). 



Fio. 3. >Strati:;/us titanus; the larva 

 (about natural size), 

 object tlie investigation of the then conditions of the hard 

 back grubs in those two I'residcncies, and the information 

 obtained at that time was included in Pamphlet No. 75 

 already mentioned. 



SITUATION IN ST. KITTS. The Small brown hard back 

 •which occurs in St. Kitts as a pest in sugar-cane fields is 

 Lachnosterna patruelis. This insect was found by the 

 Entomologist in 1912, occurring in large numbers in the 



Fig. 2. Larva of L. tuimdoms. 



soil of a sugar-cane field, where the canes were suffering badly 

 from drought, the effects of root disease, and the attacks of 

 termites and other insects. There were so many influences 

 adversely affecting the health and condition of the cunes that 

 it was not possible to form an ojiinion as to the exact part 

 played by the hard back grubs. 



These grubs are parasitized by some hymenopterous 



insect, in the same manner as Phi/talus smithi in Barbados is 



parasitized by Tiphia parallela. 

 Tix>hia parallela occurs 



abundantly in St. Kitts, at 



certain times and in certain 



localities at least, and it 



may not be too much to 



assume that this is the 



jiarasite of Lachnosterna 



patriielii; but this point has 



not yet been proved. It is 



important that the adult 



should be raised from some 



of these parasitic grubs in 



order that the parasite may 



be identified. Since the first 



record of Lachnosterna patruelis as a probable pest of sugar- 

 cane in 1912, this insect has been found frequently in the 



soil of sugar-cane fields, and it is believed to be a pest of 

 some importance as a root feeder: 

 it seems to be specially important in 



f connexion with attacks of root fungus. 



SITUATION IN ANTIGUA. The 



\ brown hard back of Antigua is 



Lachnosterna sp. For several years 

 there have been complaints that 

 grubs were seriously injuring sugar- 

 cane in that i.sland. On investiga- 

 tion it always happened that very 

 few grubs were to be found, until 

 at the end of 1911, a field of onions 

 of about 7 acres was very badly 

 injured, almost completely destroyed 

 in fact, and the hard back grubs 

 were then found in great numbers. In 1914 the Entomo- 

 logist found this insect in large numbers in ripening Indian 

 corn which showed the effects of severe root injury. During 

 1915 two sugar-cane stools were .sent from Antigua to the 

 Head Office. From 

 the soil attached to 

 the roots of these 

 canes thirty-six well- 

 grown hard back 

 grubs, presumably 

 grubs of the brown 

 hard back, w e r e 

 obtained. 



The account given 

 in Pamphlet No. 75, 

 p. 12, of 1,000 ol 

 these grubs beini,' 

 collected per acrr 

 in the soil of an 

 Indian corn field, Fi< 

 and the presence of 

 as many as thirty 



six grubs in the soil adhering to the roots and biises 

 of two stools of ratdon canes, would seem to indicate that 

 these grubs are capable of occurring in numbers sufficient to 

 cause considerable injury to growing crops. 



V 



Fii!. 5. Brown hard 



back, Phytalus 



smithi (natural 



size). 



t. Larva of P. smithi attacked 

 by larva of Tiphia parallela. 



