122 



THE AGRICULTURAL XIAYS. 



April in 



1915. 



INSECT NOTES. 



Tins 

 ing grubs 

 complei in-. 



adults. 



bOIL-INHABITING GRUBS. 



is the season of the year when certain soil-inhabit 



which attack some of our West Indian crops tre 



their larval growth andare about to emergi is 



Diaprepi s abbreviatus. 



These insects are of two general kinds: the root borers, 

 Diaprepes abbreviatus, Exophthalmus esuriens, and perhaps 

 other closely related species, and the hard back group 

 including Pkyialus smithi, several species of Lachnosterna 

 and Cyclocephala. 



Readers ol the Agricultural 

 Keivs will remember that early 

 last year (April 1911) the 

 Leeward Islands runt bona ap- 

 peared iii great numbers in one 

 district in St. Kitts. The adult 

 insects were found in a cotton 

 field in such abundance that 

 some lo,000 were reported to 

 be captured in a short time. In 

 an adjoining field, ripening cane 

 plants were obviously suffering Fn 

 from some disease or pest, and 

 examination revealed the pres- 



ence of enormous numbers of the grubs of Exophthalmus 

 eniriens, attacking the underground portion of the canes. 

 This insect became abundant in lime trees at Montserrat 

 about the same time, and at Antigua on limes about 

 a month later. The injury caused by the 

 adult beetle is not \ei\ severe. The root 

 injury caused by the grubs may be con- 

 siderable in the ease of limes i in sugai 

 cane. 



Diaprepes abbreviatus, which is the 

 root borer of sugar-cane in Barbados, 

 occurs in several of the West Indian 

 islands where it may be a pest of 

 sugar-cane, limes or cacao. Of the 

 hard back grubs which are known to be 

 or are believed to be injurious to growing plants, it is 

 lik"ly that in each island one or more species will be 

 found. In St. Kitts, the small brown hard back, Lachnosterna 

 patruelis, is abundant in the cane fields of certain districts. 

 In Antigua, Lachnosterna sp., a slightly larger brown 

 hardback, is known as a pest of Indian com and young cane 

 plants, and it has in one instance at least proved destructive 

 in onion cultivation. In the Windward Islands 

 there ail- several species of Cyclocephala and 



Leucothyreus which occur as hud back pests of 

 various crops. 



The adults of the root borers, Exophthal 

 nms and Diaprepes, after emergence take refuge 

 among the foliage of plants. Exophthalmus may 



be looked for among the leaves ol lime trees, 

 pigeon peas, castor plants, and French cotton, while 



Diaprepes hides in the corn, sugar-cane, ami 



amongst the foliage of other plants which may 



grow in or near tl gar cane fields. 



The larVac of these two beetles feed oil the 



plants of many kinds. 



Fig. 3. Diaprepes abbreviatus; th 



The hard back beetles are more difficult to find as they 



col it from the soil during the night and burrow down 



igain and remain buried during the day. The hard back 

 grubs will be found in the soil amongst the roots of cane 

 and com. probably pretty close to the plant and nol rery 

 much out in the banks. 



Both the root borer weevils and the hard back 1 ties 



eat the leaves of plants to some extent, and their presence is 

 often revealed bj leaves with ragged edges, and with holes 

 eaten through them. 



This is the time to keep a careful watch lor tl :cur- 



rence of these beetle-. In any cane field in which canes have 

 appeared to be dying of drought just before ripening, careful 

 examination should be made for the grubs of these In .ties, 

 and if they occur there, the stumps should be dug out as 500D 



a- the canes are reaped and 

 broken up so that the birds, 

 ants, and toads may have an 

 opportunity ol getting at them. 



Where these signs ale -ecu, 

 search should be made among the 

 foliage for the root borer adults, 

 and in the soil near the ha- I 

 the plants for the hard hacks. 



A little later, probably with 



Fig. 2. Exophtftahnus tic first rains, the adults will 



esuriens; the adult, be emerging, and as they are 



seen, regular collections should 



lie made in order to prevent egg hiving as far as possible. 



'The planter should know which tields the beetles are 



coming from and should make vigorous efforts to prevent 



tin- infestati f any others, by collecting and destroying 



the beetles, bj digging the stumps 



and exposing the grubs or collecting 

 them. The eggs, also, of the 



borers maj be collected, since these 

 are often deposited in situations where 



they may be easily found. These i [ 

 arc laid on leaves of cane, com, cas- 

 tor, etc., and they are covered from 

 view by means of a bit of leaf stuck 

 down over them. The figure shows 

 the general appearance of the root 

 irrangenient on the leaf. 



ties and their eggs IS 



borer eggs and their 



The collection of the root borer bi 

 a very useful practice when they occur iii abundance, and it 

 is quite easy to train young boys to find them readily. 

 When tiny have once learned how to search and where the 



beetles hide and where the eggs are deposited they become 



very proficient. Many planters do not have this kind of 



work performed because tiny think that if their 



neighbours do not cooperate in the practice, no 



C 1 will result. It is of course desirable that 



collecting should be energeticallj carried .m 



throughout each infested district during the 



season of emergence ol the beetles and ol 



laying. Much maybe accomplished, hov 

 by any individual planter working alone. 



to. I. Phytalus tmithi. 



In the case of the hard back the matter ol 



ting the adults ami eggs is more difficult, 



but the grubs maj be collected easily in. I 



roots of often In large numbers from tields of Indian coin, and 



At this time of the year those in the a fair degr f I trol may be maintained m this 



cane field will be found in the underground portion of the 



, svhere they are eating the inside part of the plant. II. A. P.. 



