106 



THE AGRICaLTURAL NEWS. 



April 1, 1911. 



INSECT NOTES. 



THE MOLE CRICKET IN TRINIDAD. 



Dr. Fredholm read a paper before the Agricultural 

 Society of Trinidad and Tobago on December 20, 1910, on 

 the mole cricket (Smjiteriscus didactylus). This paper was 

 published in the Proceedings of the Society for February 

 1911, page 1.53. 



Mention has been made of the mole cricket in the 

 Ai/ricultural Netvs at various times, and in the Insect Notes 

 entitled Crickets, in Vol. VI, p. 106, the previous references 

 to this insect are given. It is also stated that there are tvfo 

 other species of mole cricket known in the West Indies; 

 these are Scapteriscns variegatus axiA. Grytlota/pa hexadactt/la. 



The mole cricket appears to be a more serious pest in 

 Trinidad than in the smaller islands, and a brief abstract of 

 Dr. Fredhohii's paper may be of interest to readers of the 

 Ayricult aral News, since this is based on extended experience 

 and observation. 



It is estimated that the damage by the mole cricket in 

 Trinidad amounts to about §1.5,000 per annum, and this 

 amount of loss, together with the difficulty with which 

 it is controlled, makes this insect a pest of importance. The 

 mole cricket lives underground, in galleries which it 

 tunnels for itself, during the whole of its life-time. The 

 adults sometimes come to the surface at night, but during 

 the day they remain hidden. It is not difficult to determine 

 the location of their galleries, since these are generally so 

 near the surface that they are indicated by the loosened and 

 slightly raised earth which forms the top of them. These 

 galleries ramify, running in all directions on the level, 

 and descending into the lower soil. It is noted, however, 

 that mole crickets rarely inhabit any but very level spots and 

 that their superficial galleries seldom extend upwards when 

 any slight elevation is encountered. 



The mole cricket is very powerful in the matter of bur- 

 rowing through the soil; but on the surface is very awkward 

 in walking and jumping, and feeble in flight. Its food is 

 largely the underground portions of plants, and when small 

 plants are cut oft' near the surface and fall within the 

 reach of the insect, the leaves and tender stems are also 

 eaten. Earthworms and insects smaller and weaker than 

 itself are often killed and eaten by it, when these are encoun- 

 tered in the galleries. 



Mole crickets have .several natural eneniie.s in Trinidad, 

 the most important of these being insectivorous birds, the 

 savannah blackbird ((Juiscalus crassirostris), the tic'k bird 

 (Crotophwja aiii), and the qil' est ce qu'il dit {Lav ins pilunga). 

 which feed freely on these insects wherever they are found, 

 and are very persistent in hunting them out. They snap 

 them up quickly whenever the in.sects appear above ground, 

 and they also carefully scrutinize the raised top of every Imr- 

 row, and when any movement of the soil indicates the pres- 

 ence of an in.sect beneath, the birds break through into the 

 gallery and capture the insect. Fowls also search diligently 

 for mole crickets, scratch them out of their galleries, and eat 

 them. Ground lizards and toads, too, are natural enemies of 

 this insect. 



Many remedial measures have been tried from time to 

 time, but only a few of them have proved entirely satisfactory. 

 In the protection of small areas, as in the case of provision 

 grounds and gardens, no great difficulty should be e.tperi- 

 onced if war is persistently waged on this pest. Before 

 |ilanting, the soil should be thoroughly turned up by forking 

 or ploughing, thereby e.xposing the mole crickets to their 



natural enemies. A trench about 1 foot wide should be dug 

 round plots of this kind. If the ground is left clean for .some 

 time before planting, the absence of food will have a tendency 

 to force the insects to seek other feeding ground.-*. Hand pick- 

 ing after heavy showers will result in the capture of large 

 numbers, when they are driven to the surface to escape from 

 drowning in their burrows. 



Poisoned baits have been found useful, the most effi- 

 cacious poison being arsenic or some arsenical compound. 

 The baits are prepared with some favourite food plant 

 of the pest, which is cut or chopped into fine pieces, slightly 

 moistened, and thoroughly mixed with a small amount of 

 white arsenic or Paris green. This maj' be distributed along 

 the rows of plants where the insects feed, either on the top 

 of the soil, or slightly covered with it. Poisoned bait used 

 in this manner has the objection that it may be eaten by 

 fowls and useful birds. A valuable substitute is a bait 

 made by using fresh horse dung to which poison has 

 been added; mole crickets are very fond of this, and there is 

 less danger of its being eaten by their natural enemies than 

 when ordinary food baits are used. Mole crickets which have 

 been poisoned immediately retreat to their burrows and die 

 in the ground, out of the reach of birds. Voung plants 

 in nurseries can be protected by placing around each 

 a screen made from banana leaves, leaves of mammee apple, 

 or a wire screen, or even .short sections of bamboo. For the 

 treatment of lawns, strong soap solutions have been found 

 successful; these are merely poured on the ground, and serve 

 to drive the mole crickets to the surface, when they should 

 be collected by hand, as the soap and water does not kill 

 them. For protecting large areas, it is suggested that light 

 traps should be used. These are made by suspending a bright 

 light over a tray containing water, on the surface of which 

 is a film of oil at least ,V-iich in thickness. They have been 

 found fairly satisfactory, but it is worthy of note that the 

 number of males caught by these traps is greatlj' in excess- 

 of the number of females. In conclusion, it is stated that 

 the most effective and economical method to pursue is the 

 protection of the natural enemies, especially birds, which 

 exercise such a large influence over the extent of the occur- 

 rence of this pest. 



THE GREEN SCALE. 



In the report of the Government Entomologist of Ceylon 

 for 1909, mention is made of the green scale {Coccus viiidis 

 [Lecanium viride]) which was a serious pest of coflTee a few 

 years ago. Since the abandonment of coffee cultivation, this 

 insect has shown a tendency to establish itself on tea in cer- 

 tain districts, and in one area it has assumed the proportions 

 of a .serious pest. At the time of the writing of the report, 

 it was largely abundant in one district only, but there are 

 indications that it may become a pest of tea. 



The Entomologist could not account for its prevalence 

 in only one district in destructive numbers, since it had 

 been equally abundant in all the coftee-growing districts, 

 and is still generally distributed throughout the island; 

 besides, there seems to be no reason why it should not adapt 

 itself to act in one section as well as another. 



The suggested control measures aio the burning of 

 prunings, and the spraying of the trees with kerosene emul- 

 sion, except when 'Hushing", when a simple mixture of soap 

 and water should bo used. 



The reiudval of the wild food plants from the vicinity of 

 tea cultivation is recommended, in order that re-infestatioa 

 may not so readily take place from outside. 



