250 



KNOWLEDGE & SCIENTIFIC NEWS. 



[Oct., 1904. 



Conducted liij F. Shu.lington' Scales, f.r.m.s. 



CoccidsLe. 



WitK Notes on Collecting and 

 Preserving. 



By Alice L. Emhli;tox, B.Sc. 



[Continued from page 224.) 



As regards the possible introduclion of the San Jose 

 into Europe, there is little cause for alarm, for the 

 climatic conditions and the character of fruit-growing 

 in this continent would make it hard for this scale ever 

 to become a serious factor here. 



In the West Indies enormous damage is done to 

 crops of all kinds, and yet it is only within the last 

 decade of the 19th century that attention has been 

 paid to scientific work on economic entomology. The 

 sugar-cane pests in particular are responsible for a 

 heavy, regular loss to the planters ; investigations are 

 now, however, being carried on with a view to finding 

 remedies and controlling methods. 



It is best to begin with measures of quarantine 

 against the introduction of new diseases. Preventive 

 measures ought to be adopted, for it is of enormous 

 importance if an outbreak of a disease can be avoided, 

 and it is only by a knowledge of the life-histories of the 

 pests that an attack can be predicted and controlling 

 conditions set up, such as, for example, alternation of 

 crops and trap-crops. If, however, the insect is 

 already established, then suitable remedial measures 

 must be applied, either by the direct use of poisons, or 

 by the indirect control through the presence of enemies 

 to the injurious insect. Fortunately for the horti- 

 culturist, Cpccidae have innumerable enemies, and the 

 problem of their control is largely solved by the action 

 of checks provided by Nature, such as birds, lizards, 

 bats, etc. Apart from these there arc the multitudes 

 of insects that prey upon Coccidae, either as predators 

 or parasites ; these tend, in a state of nature, to keep 

 the balance right, but this equilibrium becomes much 

 upset by the artificial conditif)ns set up in cultivated 

 countries where it is impossible to avoid this disturb- 

 ance of the influence of natural checks. 



The Coccidae are hosts for numerous minute insect 

 parasites, as well as being food for the predaceous 

 ladybird beetles (Coccinellidae), which are among their 

 most important natural enemies. Among the many 

 thousands of minute Hymenopterous insects in the 

 world to which have been given the popular name of 

 " Chalcid flies," there is prob.ably no single family 

 that is of more interest and importance from an 

 economic point of view than that of the Encyrtidae. 

 The various species composing this family, like the vast 

 majority of Chalcid flies, live parasitic.illy in the eggs, 

 larvfe, pupse, and imagoes of other insects, and hardly 

 a single order of six-legged insects is wholly free from 

 their attacks. But in this family, and more especially 



in the sub-family Encyrtinae, the species are of more 

 particular interest and importance for the economist, 

 since so many of them are found attacking and destroy- 

 ing Coccidae. The work on the development and life- 

 histories of these small creatures is of necessity very 

 minute, seeing that the hosts are usually only one or 

 two millimetres in length in the adult condition ; and 

 yet little can be done in the matter of encouraging these 

 beneficial creatures unless their life-cycles are well 

 known. Much of the work demands special methods 

 for the microscopic preparations. To illustrate this we 

 mav take the well-known brown scale on ferns and 



5 tn.m.- 



Fig. 1. 



EXPLANATION OF FIGURES. 



Portion of Fern=frond attacl^ed hy Lecanium hemi^phacricum \ar. 



/iltciiin, the Coccid being parasitised by Comyz in/vlix. 



Egg before separation of the two masses. 



Egg after losing the >olk = niass. 



First observed larva with bifurcated tail. Length. '75 mm. 



Larva showing spiracles. 

 — Prepupa in situ in the host, inverted position. /i^host; 



/■ = parasite; pi plates. 

 -Cpmys iu'lUx. j, dorsal view. Length, 2 '.s mm, 



awn by F. ShiUiugton Scales after dtai^'iiiris by Miss A. L. Embleion, 



palms {Lecaitium hemisphaericum), which is parasitised 

 to an enormous extent by a minute Encyrtid (Comys 

 infelix). On a fern frond that has, say, 200 Coccidae 

 upon it, at least 190 of these will be killed by the 

 Comys. The female of this little fly measures 2.5 mm. 

 in length, and is black, with fuscous patches on its 

 wings. It is very curious that the male is extremely 

 rare, for whereas the females occur in myriads, the 

 males have only once or twice been obtained. In many 

 ways the life-history of this fly, as far as at present 

 known, is extraordinary and unique. The newly- 



