278 



KNOWLEDGE & SCIENTIFIC NEWS. 



[Nov., 1904. 



Conducted hy F. Shillington Scales, f.r.m.s. 



CoccidoLe. 



With Notes on Collecting and 

 Preserving. 



By Alice L. Emlilhton, B.Sc. 



{Continiud from page 251.) 

 I-KOM lliis laricl .sketch of some of the puints in the 

 life-history of Comys mfelix, it can be gathered that 

 very special microscopic methods are required to do 

 such a piece of work on Coccid parasites. It has been 

 found that the eggs can be sectionised while still in the 

 abdomen of the fly. The best fixing reagent has been 

 found to be Gilson's fluid (the formula for which will 

 be found in a footnote), used cold. The specimens 



Formula for Gilson's Fluid : — 



Nitric .\cid, 46° .. .. .. i9'5 cc. 



Glacial .\cetic Acid .. .. 55 cc. 



Corrosive Sublimate .. .. 23 75 cc. 



Alcohol, 60 per cent. . . . . 125 cc. 



Distilled Water . . .. .. noo cc. 



were left in nearly half-an-hour, then washed very 

 thoroughly in 70 per cent, alcohol, and so gradually 

 taken to absolute alcohol, cleared in cedar wood oil, 

 and fixed in paraffin (not too hard — certainly not more 

 than 52 degrees melting point). The sections give best 

 results for nuclei of eggs when stained by the iron- 

 akmi-ha-m.-itoxylin method, with eosin as the second 

 stain ; the nuclei in such preparations show their struc- 

 ture very clearly, and the mounts are permanent. 

 The youngest little white larvee are best seen in water 

 or dilute glycerine, the trachea;, then remaining full of 

 air, show up dark and well-defined. For some struc- 

 tural points it is well to treat them with very weak 

 osmic acid, or, better still, expose them for a minute or 

 two to the fumes of osmic acid over the mouth of a 

 bottle containing it. It is inadvisable to use alcohol 

 with these larvse, as they shrink, and very little can be 

 ascertained from such specimens. Some aqueous 

 stains take well on these larvcP, but on the whole those 

 mounted in water or dilute glycerine, unstained, seem 

 the most satisfactory, though they have the disad- 

 vantage of not being permanent. 



The crystal-containing envelopes are best seen by 

 polarised light. The microchemical tests to prove 

 these crystals to be uric acid also need special care and 

 methods. Many of the other points in such an 

 investigation as this must be confirmed by means of 

 serial sections, to prepare which it has been found best 

 to fix the specimens in Gilson's fluid, the nitric acid of 

 which serves to soften the chitine. \'arious stains may 

 be used, hut to see nuclei the iron-ha'matoxvlin and 

 cosin will be found to be as good as any — or with 

 (jrubler's orange G instead of eosin. 



The above gives an inadequate account of the 

 methods of investigating some of the finer points in the 



developing and life-history of a Coccid parasite, but, 

 perhaps, it would not be out of place here to give some 

 general directions for collecting and preserving Coccidae 

 themselves. Such directions have been given over and 

 over again by entomologists of all countries for the 

 collecting and preserving of Coleopicra, Lepidoptera, 

 etc., but Coccidae are not, and never have been, 

 favourite insects for the collector, and so it may not 

 be superfluous to give here some notes as to the best 

 methods to be employed for collecting and preserving 

 these interesting but much-neglected creatures. They 

 differ so widely from other insects that special methods 

 are necessary. There is a great field for the collector 

 in Coccidology, as collections have been made from 

 very few parts of the world, for, whereas very repre- 

 sentative collections exist of other insects from North 

 and South .'\merica, most European countries, Africa, 

 New Zealand, and India, yet the Coccidae are practically 

 unknown. The collections that do exist are at best 

 very local and very incomplete. This is all the more 

 extraordinary when one remembers how destructive 

 Coccidae are, especially in tropical countries, where they 

 are conspicuous on almost every plant. This neglect 

 has not come about because these creatures are in any 

 way specially difficult to deal with, for they are re- 

 markably easily collected, and immense numbers can 

 be packed in very small space, and sent through the 

 post without harm befalling them. 



As regards localities, though Coccidae are found 

 north and south of the fortieth parallels, yet they can- 

 not be looked upon as abundant. Search for them will 

 be best rewarded in the warmer temperate zones, and 

 in the tropics, where there is a vast unworked field of 

 investigation that would richly reward the entomo- 

 logist. They are found chiefly on trees and shrubs, 

 ferns and palms ; much collecting may be done by those 

 who receive plants from the tropics, and importers 

 have great opportunities not only for collecting these 

 insects, but also for preventing the introduction of 

 harmful species. 



In collecting it is best to simply gather portions of 

 the host plant without disturbing the parasites, and to 

 get plenty of the material, and both sexes where possi- 

 ble. In preserving it is well to avoid alcohol, for 

 specimens collected in this way are often useless and 

 cannot even be identified ; however, it is sometimes 

 iiselul lor the softer species, but, as much as possible, 

 Coccidae should be preserved dry. Flat card boxes 

 serve the purpose best, though envelopes are useful ; 

 yet boxes have the advantage of saving any parasites 

 that may emerge ; a full description of locality, date, 

 etc., should be written on each. Tin boxes being air- 

 tight give rise to mould, and should therefore be 

 avoided. With those specimens which are too fragile 

 to preserve well, a rough sketch of their form should 

 be made. To keep permanently, place the Coccidae in 

 glass tubes, with cotton wool stoppers until the speci- 

 mens are quite dry, and then later put in india-rubber 

 stoppers. 



To mount for the microscope, it is first necessary to 

 boil away all the soft parts with caustic potash, and 

 then mount in Canada Balsam, after the usual washing 

 dehydrating, and clearing procedure. 



A Means of Ma^rking the Position of 

 Objects upon the Cover- Glass. 



It is often necessary to mark upon the upper surface 

 of the cover-glass the position of objects mounted be- 

 neath it, but it is by no means easy to do so without 



