INSECTS AND WEATHER

Evening Post, Volume CXVI, Issue 24, 29 January 1934, Page 16

INSECTS AND WEATHER

RECENT INVESTIGATIONS Thie chief work of the entomological department at Kothamsted Experimental Station, according to the annual report of the institution, is the study of the factors, .determining, the size of insect population. Insect pests are always with us, but so long as their numbers are small they are comparatively harmless. Sometimes, however, one species begins to multiply, and it 3 power to increase is so enormous that the harmless few speedily become a serious pest, causing great loss of crops. Hitherto: the factors responsible for this rapid multiplication have been but little known, and consequently it Ims not been possible to«takc preventive steps beforehand, or even to warn farmers of the probability of. attack. This subject is now under full investigation at : Eothamstod. , Soon after Dr. C.B. Williams entered on his duties as head of the department in July, 1932, ho began an investigation into the relation of insect's' numbers to weather conditions! The great difficulty has been to find some numerical expression of the.abundance of insects. Dr. Williams is trying to 'Ovcrcomo this by taking- daily samplps of all flying insects uuder' definite standard conditions and' ' identifying and counting them. ; He- does this by means of a light trap, operating, from 'sunset- to 6tinrisc, and .fitted with a mechanism for dividing the period of operation, into eight sub-periods, so as to show the- '-nctual' hours during which ''each catch of insects is obtained.' ■.: • The trap 'is near to the meteorological enclosure/ so that the- precise meteorological conditions during each subperiod are "known. All the'working conditions, including the intensity of thp light, arc standardised, so that the catches of each season may be compared with those of any other. It is lioped: in time,, to obtain data from which relations between weather conrditions and rate of multiplication of insect population may be worked out. It does not necessarily follow that a large catch of insects, means a large multiplication of the local population. Insect migrations are .known to occur, andrsteps: are now being1 taken to follow then). A migration of small cabbage white butterflies was observed at Rothamsted in mid-August, 1932. The horde was traced to the Norfolk coast, where, it. had arrived presumably from the Continent. It had travelled westward, passed over Hothsunstcd, niid the, resulting larvae did a good deal of damage to s cabbages in September. ■ Another factor'affecting the- size, of the insect population'is the degree of parasitism. This is being studied by I)r. Barnes, using certain of the midges as, the test insect. ' "An .interesting observation was made on two of the grass plots by Dr. Siiurgii, in slu'dying one of the thrips infesting the grasses..Where the grass land h:ul been treated with lime, about 12 to 20 per cent, of the'thrips were parasitised by a ncmstodc. Where, however, tire grass J.nnd had received no lime, the thrips were free from parasites. This is. jiow being further investigated, SPRINGBOARD DIVING .•_= .«. ■ . '".'.'... ~ EBISBANE, January 2S. At the Australian swimming championships the low springboard diving resulted: -Masters (Victoria), 1; Tickle (Now South Wales), 2; Mott (Victoria), 3. ■ KxprcsK railway locomotives in Ijiitnin criiT.v aboul IS tons of ivatw in their tendaw- ■ .