THE WOMBAT. 83 



As a rule Coccids are injurious to vegetation, especially 

 in warm and temperate regions. They have been reported 

 from all parts of the world — from " China to Peru " — and 

 perhaps Australia furnishes a greater number than any other 

 •country yet known. In cold climates they only occur in hot 

 houses and green-houses, therefore gardeners are often 

 familiar with them. As there is scarcely a eucalypt in 

 Victoria free from Coccids, the student of the family has 

 unlimited scope for observation. Of course there are such 

 insects as Pseudococcus casuarinc?, Maskell, which appear to 

 have a very restricted range, the one named being, so far as 

 I know, only recorded from Myrniong. In 1891 I furnished 

 specimens of this insect to Mr. Maskell, who named it, and 

 included it in his paper of 1892, N.Z. Trans. It was 

 plentiful in 1891, yet since then I have been unable to find 

 any trace of it. In the specimens observed (perhaps several 

 score), no sign of parasitism was discovered. Can anyone 

 suggest why certain insects appear in unusually large numbers 

 after an almost entire absence of them for several years ; or 

 why others disappear equally suddenly. It is all very well to 

 say "natural conditions" were favourable or unfavourable (?) 

 But what conditions could be unfavourable to insects such as 

 Pseudococcus casuarince, where no parasitical enemies are 

 known to exist. The Coccids of Victoria present many such 

 interesting and peculiar phases well worthy of consideration. 

 There are already many Coccids in this colony imported from 

 other lands, and as they are so easily brought on trees or 

 plants — even on sawn or hewn timber — it is not to be 

 wondered at. In these days of rapid communication many 

 Coccids are thus spread over the world, and it is unfortunately 

 too often the case that insects thus introduced find more 

 suitable quarters in their new home, and in the absence of 

 their natural enemies often become serious pest's. For 

 instance — " The Cotton Cushion Scale " (Ice'rya purrliasi 

 Mask.), which was accidentally introduced into North 

 America some years ago, threatened the extinction of the 

 orange groves in California, and this was only prevented by 

 the timely introduction from Australia of Vedalia cardiualis, 

 a parasitic coleopterous insect, which luckily soon stamped 

 ■out the pest. Lecanium hesperidum, Linn., has clearly thus 

 been scattered far and wide over the earth's surface, and 

 Dactylopius adonidum, Linn., bids fair to have a world-wide 

 distribution. 



A few remarks about the principle of Coccid classification 

 may not be out of place. Systematic working entomologists 

 find it necessary to amass collections, and the time has 

 passed away when two or three specimens were considered 

 sufficient to represent a species in a collection, indeed forty 

 •or fifty, or even one hundred specimens are now necessary to 



