Vol. XII. No. 269. 



THE AGRICULTURAL NEWS. 



171 



The larvae of the weevils referred to in these nott'S are 

 all whitish grub.s without legs; the larvae of the hard backs 

 are all similar to each other in the tact th.u they possess three 

 pairs of slender legs, und a long swollen al'domen or hind- body. 

 They are also whitish in colour, but at the hind end of the 

 body the dark contents of the anal pouch shows through the 

 body walls, giving a dark appearance to this portion. 



XATUr.AI, £NE.MIES. 



(1) Of the adults. 



Birds, lizards and toads are recognized as being insect 

 ■feeders, and it is likely that they aie the most erticient 

 natural enemies of the adult forms of the insects considered 

 in this series of articles. 



The large weevils generally hide during the day among 

 l,he leaves of plant.s, often remaining motionless and well 

 concealed for a long time, and it is likely that as long as they 

 remain perfectly quiet many of their enemies fail to observe 

 them. The hard backs, on the other hand, emerge from the 

 ■soil at night and return to hide there during the day. The 

 toad feeds at night, largely, and on this account is able to 

 capture large numbers of hard back beetles among the 

 nocturnal insects which comprise its food. The predaceous 

 enemies which capture only the adult insects cannot have 

 a very great influence on the numbers or rate of increase of 

 any of these beetles, since many of those which are devoured 

 are captured only after they have fulfilled their sexual 

 functions, that is, after mating has taken place and many 

 eggs have been laid. 



(2) Of the larvae. 



The larvae of the weevils and hard backs live in such 

 -situations that they are ordinarily protected from the attacks 

 of such (.'redaceous enemies as birds, lizards, and toads. 

 "When, however, they are e.xposed, as in ploughing or forking 

 in the field, or in breaking up infested cane stools or dig- 

 ging over manure and megass heaps, they are immedi- 

 ately open to attack mainly by birds and ants, and to a slight 

 •extent also by lizards and toads. 



The most etticient form of control is found in the case of 

 those insects which act as parasites, laying the egg in or on 

 the immature form of the host insect, and thus providing for 

 the sustenance and development of the young at the expense 

 of the life of the host. 



The root borers of the sugar-cane in Harbados and the 

 Leeward Islands are not known to be attacked by parasites, 

 Isut the Fiddler beetle of Jamaica is attacked by a burrowing 

 •wasp, Elis atrata. I'liytalus siiiithi and Ligyrus tumiilosus 

 are attacked by other burrowing wasps of the same family, — 

 the Scoliidae — the parasite of the former being Tiphia 

 _pxralella and of the latter Dielis dorxata. The parasite 

 larva discovered on the grub of Lacfmosterna patrHeh'f! in 

 St. Kitts was most likely that of a Scoliid wasp. 



It is very probable that in the case of all these beetles 

 there are parasites exercising a greater or lesser ilegree of 

 control, and that more extended observations on the life cycle 

 of these insects will reveal the presence of these beneficial 

 insects. 



The burrowing wasps, some of which are known to be 

 ^xvrasitic upon soil-inhabiting grubs, belong to the family 

 Scoliidae, of the order Hymenoptera. It is of interest to note, 

 that among these insects are to be found .some which attack 

 grubs of the I.amellicorn or Scarabeid beetles, of which one at 

 'least is a parasite of the grub of a weevil of the sub-order 

 Mhynehophora. 



The adults of the Sooliid wasps often exhibit a consider- 

 able dirterence of appearance between males and females. 

 In the case of Tiplaa parahlla, the distinction is mainly one 

 ■ of .size, the female being much the larger, The colour is 



very similar in both sexes, being black with faint lighter 

 markings. DidU dormta, on the other hand, shows a differ- 

 ence in both size and colour markings between the males 

 and females. The female is slightly larger, with large red 

 spots on the dorsal surface of the abdomen, whilst the male 

 in addition to being smaller, shows bright lemon-yellov/ 

 njarkings. 



These Scoliid wasps are to be seen in cultivated fields 

 and other situations throughout the West Indies. The 

 habit of flight is the same in all — a quick, almost darting, 

 motion, low down, often just skimming the surface of the 

 ground. They frequently alight for a moment as if to 

 inspect the ground, and then resume the characteristic flight. 

 Sometimes, however, they immediately burrow into the 

 ground. This they do quickly, disappearing within two or 

 three minutes. 



Tn the case of DiulU dorsain,, when the sexes can easily 

 be distinguished during Hight, it is noticed that the females 

 generally burrow into the soil, altho-agh the males have been 

 observed to do so also The female wasp is in search of the 

 grubs in the soil, and when she finds one of these she sting-i 

 it and deposits an egg on the skin of the grub. This egg 

 hatches and produces a parasitic grub, which attaches itself 

 by means of its mouth parts and feeds on the body contents 

 of the beetle grub, probably not causing its death until it 

 (the parasitic grub) is nearly full-grown and ready to pupate. 



In the case of many of the parasitic Hymenoptera, the 

 eggs are deposited within the body of the host, and the 

 parasitic larvae live and complete their larval development in 

 this situation. Certain other hymenoptera capture insects 

 and spiders, and sting them to produce immobility or paraly- 

 sis, but not death. The paralysed prey is then used by the 

 hymenoptera to store its nest, thus providing living food for 

 its young. 



Thus the method of the Scoliidae in this matter )( 

 providing for their young, appears to be intermediate between 

 the two methods described above. The host is stung 

 and more or less paralysed, but is not carried away; the 

 egg is placed on, and not in, the host, and the parasite grub 

 lives on, not in, the host. 



In the succeeding issue of the Agricidtaral News will be 

 presented a table summarizing the information given in the 

 foregoing articles. 



The Educational Value of Agriculture.— 



Some of the advantages of instruction in elementary agricul- 

 ture are described in the ICfperiiiienl Station Record for 

 November l'.M2. It is pointed out that when well given, the 

 advantages of this instruction are as follows: (1) it commands 

 from the beginning a wide range of the interests most common 

 to children; ('2) it forces measures and comparison and judg- 

 ment thereon, upon the t;hild at every turn; (.3) it trains 

 a child to be careful, exact, patient and persistent; (4) it 

 otfers in the gardening work all the elementary problems of 

 form, colour and proportion, and so lays the foundations of 

 a sense of beauty; (5) it att'ords abundant opportunity for 

 emulation and cooperation; and (6) it teaches boys and 

 girls to work. In<uomuch as it discourages pure reasoning, 

 students should also be taught pure mathematics, logic and 

 languages. The author points out that 'our trouble in the 

 past has been that we have tried to take our school children 

 directly into this abstract world of direit thinking and 

 exalted feeling without passing them through the prelim- 

 inary stages of concrete experience, elemental virtues and 

 active self-expressions.' 



