186 



THE AGRICQLTUKAL NEWS. 



June 11, 1910. 



INSECT NOTES. 



THE HARDBACK BEETLES. 



There has been reported recently in Barbados the occur- 

 rence in unusual numbers of a beetle similar to the ordinary 

 hardback {Ligi/vus liimu/osus). For the purposes of distin- 

 guishing between these two insects in this short article, it 

 might be well to designate the commoner form as the black 

 hardback, and the one at present under discussion as the 

 brown hardback. The black hardback is of fairly common 

 occurrence and has been mentioned briefly in recent num- 

 bers of the A;/ricii!tii^'al Neii:x(see Vol. IX, pp. .58 and 106). 

 It is frequently to be seen flying to lights at night, when it 

 makes itself conspicuous by its humming and buzzing and 

 knocking against ceilings and walls. The larva, or grub, of 

 this insect lives underground and feeds mostly on decaying 

 vegetable matter, although it may sometimes eat the small 

 roots of growing plants. This grub has sometimes been 

 confused, in the minds of planters and others, with that of 

 the root borer. The diti'erence between these two has been 

 explained in the articles mentioned. It may be well to state, 

 however, that the root borer grub has no legs, and is generally, 

 if not always, to be found inside the underground portions of 

 the stool of cane; whereas the grub of the hardback has three 

 pairs of thin legs, and is always to be found in the soil, 

 among the roots of plants, or anywhere where there is an 

 abundance of trash or other <.irganio matter. 



It is not supposed that the black hardback is responsible 

 for any serious damage to growing plants, either in the lar- 

 val or the adult stage. As has been already stated, the 

 larva is chiefly a scavenger, living on decaying matter, and 

 the adult does not appear to feed to any great extent. 



The brown hardback, which has been identified as Ci/cla- 

 cephala sp., is generally less abundant than the black 

 one. During the month of May, in this year, however, this 

 insect has been reported to occur in large numbers in two 

 restricted localities in Barbados, as many as 500 to 600 

 adult beetles having been captured in a single night in each 

 of these places. Most people in Barbados, and probably in 

 the other West Indian Islands, are familiar with the appear- 

 ance of this brown hardback, but very few have perhaps 

 ever seen more than two or three at a time. They are 

 attracted, to a small extent at least, to lights, and many 

 people who have seen them in their houses have regarded 

 them merely as the young or immature form of the black 

 hardback. This is, of course, not the case, as the young 

 form of a beetle is a grub, and when the insect has left the 

 grub stage, passed through the pupal stage and emerged as 

 a winged insect, it is adult and of full size, and there is very 

 little ditt'erence in a[]pearance between the individuals of the 

 same species. 



The larva of the brown hardback is not known, and it 

 may be possible that it is so nearly like the grub of the black 

 one that the two kinds have not been separated, and on the 

 other hand, it may be that it occurs in different situations and 

 under ditt'erent conditions. It is certain that the larva of the 

 brown hardback would be found to be an underground grub, 

 and it may have a habit similar to that of the black hard- 

 back; it may be entirely injurious through feeding on the 

 roots of living plants and not on decaying vegetable matter. 

 The roots of roses and other garden plants are sometimes 

 attacked by grubs in the soil, and the.se are called hard- 

 back grubs, but it may be that investigation will show 

 that this is the work of the brown hardback and not of the 

 ordinary black one. 



The attacks of the brown hardback have all been made 



at night, and a careful inspection at any time during the day 

 does not reveal the presence of these insects, unless the 

 ground at the base of the plants is carefully searched, also. 

 These beetles come out in the evening, as it gets dark ; but 

 as daylight approaches, burrow into the soil to a depth of 

 3 or 4 inches, where they remain in hiding. This habit of 

 hiding in the .soil during the day is common also to the black 

 hardback. The brown hardback attacks a great variety of 

 plants, the rose and hibiscus .seeming to be principal favour- 

 ites, and certain kinds of roses seem to be preferred to others, 

 notably, La France and Marechal Niel. A visit to these 

 attacked areas with a light at night reveals the beetles busily 

 engaged in feeding on the leaves. The mating of the sexes 

 also occurs at this time and place. The beetles are easily 

 disturbed and if the plant, or the branch on which they are 

 clinging, is shaken or jarred, they loosen their hold and drop. 

 The remedies proposed for the control of these insects 

 are of three kinds: — 



(1) The use of Paris green, in the manner in which it is 

 employed in the cotton industry, on the leaves of the plants 

 attacked. 



(2) The u.se of a light-trap, consisting of a lantern 

 standing or suspended over a tray of water to which a small 

 amount of kerosene has been added. Any beetles attracted 

 to the light will fly against the glass and drop into the water 

 below, where the kerosene will kill them. This recommenda- 

 tion is only tentative, because it is not known how great an 

 attraction the light may have for this insect. 



(.3) Collecting. Where these insects occur in large num- 

 bers they might be easily shaken, or jarred, ott' the plant into 

 a bucket containing water and kerosene. 



It is not. known what natural enemies these beetles 

 may have, but it is expected that the common toad 

 would be very useful in this connexion, for while this 

 animal has not been seen feeding on these hardbacks, 

 excremental matter has been found consisting largely of 

 undigested portions of the brown variety, and it is thought 

 that this shows the work of toads. At the present time 

 there is no record of injury to crops or plants of economic 

 importance, but it can be easily understood that insects 

 which are capable of developing in such numbers as to make 

 it possible to collect 500 or 600 in a single night in a corner 

 of a small garden, might become an extremely serious pest if 

 they should ever occur in proportionate numbers over large 

 areas. Many of the plants on which these insects feed are 

 entirely denuded of leaves. This is especially true of certain 

 roses, and the leaves of other plants have been eaten to 

 a very considerable extent. 



The Agricultural Experiment Station of the University 

 of Illinois published a bulletin (No. 116) in 1907, dealing 

 with the white grubs and Maj' beetles which occur in that 

 State. Twelve species of these insects are found there, nine of 

 which are considered t<i be injurious, and three are harmless. 

 One of the injurious species belongs to the same genus as the 

 brown hardback now under discussion — Ci/chjrephala. Two 

 of the harmle.ss forms known in Illinois belong to the genus 

 Ligyru^, and are therefore related more nearly to our black 

 hardback ( Li'iyiiis tumnhsits). This bulletin gives many 

 interesting notes on the life-history of the injurious beetles 

 and white grubs, all of which belong to the genus 

 Lachnosteriia and, it is stated, require about three years 

 for the completion of their life-cycle, the greater part of 

 which is occujiied in the larval stage. The pupal and adult 

 periods, up to the time of egg-laying, probably do not 

 last more than two or three months. The length of the 

 life-cycle of the Cydoci-phahi is not given, but it may be 

 assumed to l>e about the same as that of the species of 



