America] yield a thous and s piders , which can catch 200,000 flying ins ects ,’ says Dr.
Rupperts hofen. The tiny and delicate young of the wheel-net s piders that emerge in the s pring
are especially important, he says, ‘as they spin in a teamwork a net umbrella above the top
s hoots of the trees and thus protect the young s hoots agains t the flying ins ects .’ As the s piders
molt and grow, the ne t is enlarged.
Canadian biologists have pursued rather similar lines of investigation, although with differences
dictated by the fact that North American forests are largely natural rather than planted, and
that the species available as aids in maintaining a healthy fores t are s omewhat different. The
emphasis in Canada is on small mammals, which are amazingly effective in the control of
certain insects, especially those that live within the spongy soil of the fores t floor. Among s uch
insects are the sawflies, so-called because the female has a saw-s haped ovipos itor with which
she slits open the needles of evergreen trees in order to deposit her eggs. The larvae eventually
drop to the ground and form cocoons in the peat of tamarack bogs or the duff under s pruce or
pines. But beneath the fores t floor is a world hone ycombed with the tunnels and runways of
small mammals—whitefooted mice, voles, and shrews of various species. Of all these small
burro wers , the vo racious s hrews find and cons ume the larges t numbe r of s awfly cocoons. They
feed by placing a forefoot on the cocoon and biting off the end, s howing an extraordinary
ability to dis criminate between s ound and empty cocoons. And for their ins atiable appetite the
s hrews have no rivals. Whereas a vole can cons ume about 200 cocoons a day, a s hrew,
depending on the s pecies , may devour up to 800! This may res ult, according to laboratory tes ts ,
in des truction of 75 to 98 per cent of the cocoons pres ent.
It is not s urpris ing that the is land of Newfoundland, which has no native s hrews but is bes et
with sawflies, so eagerly desired some of these small, efficient mammals that in 1958 the
introducti on of the mas ked s hrew—the most efficient sawfly predator—was attempted.
Canadian officials report in 1962 that the attempt has been s uccess ful. The s hrews are
multiplying and a re s preading out ove r the is land, s ome marked individuals having been
recove red as much as ten miles from the poi nt of release.
There is , then, a whole battery of armaments available to the forester who is willing to look for
permanent s olutions that pres erve and s trengthen the natural relations in the fores t. Chemical
pes t control in the fores t is at bes t a s topgap meas ure bringing no real s olution, at worst killing
the fis hes in the fores t s treams , bringing on plagues of ins ects , and des troying the natural
controls and thos e we may be trying to introduce. By s uch violent meas ures , says Dr.
Rupperts hofen, ‘the partners hip for life of the fores t is entirely being unbalanced, and the
catas trophes caus ed by paras ites repeat in s horter and s horter periods ...We, the refore, have to
put an end to thes e unnatural manipulations brought into the most important and almost last
natural living space which has been left for us .’...
Through all thes e new, imaginative, and creative approaches to the problem of s haring our
earth wit h ot her c reatu res there runs a cons tant the me, the awarenes s that we are dealing
with life—with living populations and all their pressures and counter- pres s ures , their s u rges
and reces sions. Only by taking account of s uch life forces and by cautious ly s eeking to guide
the m into channels favorable to ours elves can we hope to achieve a reas onable
accommodation betwee n the ins ect hordes and ours elves.
The curre nt v ogue for pois ons has failed utte rly to take into account thes e mos t fundame ntal
cons iderations. As crude a weapon as the cave man’s club, the chemical barrage has been
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