WATER-BEETLES

Evening Post, Volume CIX, Issue 102, 4 May 1925, Page 2

WATER-BEETLES

SUCCESSIVE BRITISH INVASIONS

The collecting haliit has a firm hold upon the average schoolboy, and in choosing "Insect Collecting and What It Leads To" as the subject, of the first of Ins-six Christmas' lectures at the Koyal Institution, Mr. Frank Balfour Browne made sure of a strong appeal to his juvenile audience. And when lnj added to his fascinating story the spectacle of a glass tank containing a number of diving water-beetles his popularity was complete, and many a boy must have left the building with the' determination to follow Mr. Balfour Browne's example and become the proud possessor of a miniature aquarium, which combines with instruction so much that is pleasant and amusing.' As Lecturer in Zoology (Entomology) at the University oi Cambridge, Mr. Balfour Browne bos made a special study of the water-beetle, and on Saturday he was able t» hli ».- what a variety cf general knowledge i-;m he gained by an examination of thehabits of the fascinating little creature, l'irst of all, lie had a word io hiv about the cranky collectors. Darwin's "naturalists without souls," men who never add anything to their collections unlws l.icy have taken it themselves, and in . Uiiii connection he fold an'amutiug story of two collectors who. after a vain search for a parlj.-ular specimen, were ottered two living examples Irom his own stock. ■As a salve to conscience, they placed the unoffending crcatuvpj in. glass lubes, and by emptying the contents into tiu-ir nets, which they had ] ( iw«;rcd into ;i pond, were able to. say I hut they Had themselves taken the beetles from Ui;>. water! ' Advising his hearers to concentrate on some small group of insects,.. Mr. ISsilfoui- Brownie pointed out that, 'while-. Britain possesses more limn iO3O -diffevent kinds of hectics, thc-ro arc (•■wer than SCO in the walcv-bwlii; ■ gvw •'■ These, again, are divided into "tin!.: types, those found in ponds ami-ditches being distinct fiom those in l:tkcs. ar-i" these, again, differ from the i;ihabit-j;,u ot the livers and streams. And a curious fact in connection with this dislrij biition is that as a particular pond' changes in character with the growth oi vegetation, so the type of water-beetle changes also. It has been found, too that beetles of the brightest colours occur only in Southern or" Central England, while only the dullest colours-are' • found in the North, and tlie ■ lectureascribed the difference to the vin-,-Hmount of sunshine. Again, a. l:c rtaiM type of water-beetle is found only in the North and West, another on ] v in the South and West, a third only in the ■south and .East, and. acec-din- to the theory of Professor Edward' Korbcs each group really repiescnts a diffeieiit invasion of the country. Mr. Balfour Browne'told how, at hiibi; time or other, Britain was invad.*d by f n grOUJ? ,0t ™teii-beetles; which'- was followed by another group that .pushed tne first into the corners. Invasion m, - eeeded invasion, - with the (-ainc i-c--W» Tne smallest group to-day is that v.-hiei' inhabits the South and West [he •!->' smallest j« found in the North .•,V,,-| nest, while the South and Ea«t "ion., is a very large one, and is closely\- -I ciatcd with the general group V|>n>ad over the wliole country. The North ami West group is associated with a ,•„!.■( chmato and is believed to have conu- in ;WHh the .Ice Age. The South and V\est group, being the, smallest, therefore came „. before the Ice Age, while tlie-bouth and East group is still arrive ing We are still being invaded fromCentral Europe^ and Mr. ■ Balfour Browne, believing that England's' climate is slowly getting warmer, and will eventually return to its. former tropical condition., pictured the time vdien more and more beetles will come from the South and squeeze out the present inhabitants of the West and North *iready the-conditions are becoming too hard t for the small Lapland beetles wliicn are found only in the North, and the time wjil come when they will bfl squeezed out altogether. And, most intcrestmg of all, there are signs of a new inva^oa by an old species, for a beetle unknown in Ireland thirty veara X NnT' ex ( traolf »a»'y abundant in vest Ii??, • a"d is Pd£hinS f.ulL^~ rZtr 1 I CSe mvasions originate iv> Brown , Ur-lle' and m- Balfour hi owne, drawing an analogy from the Great War, declared that that "at I i-ophe might well be in keeping «& the general tendency of species to n cnat pait of the Continent. Subsequent lectures of the series will .-asps, caterpillars, the dragonfly -,nd the water-beetle, and, finally, w i th X j habits of insert.... flnd .' tlle wo Vof «£?