Wisconsin State Cranberry Growers Association / Wisconsin State Cranberry Growers' Association. Forty-fifth annual meeting, Wisconsin Rapids, Wis., December 2, 1931. Forty-fifth summer convention, Wisconsin Rapids, Wis., August 18, 1931
Chambers, E. L.
How nature maintains her balance, pp. 9-14 PDF (1.7 MB)
WISCONSIN CRANBERRY GROWERS' ASSOCIATION 9 HOW NATURE MAINTAINS HER BALANCE By E. L. CHAMBERS, State Entomologist When insect pests and plant diseases are as prevalent throughout the state as they. have been this season, and our shade trees are being killed by Cottony Maple Scale insects, and our alfalfa and small grain is being destroyed by army-worms and other cut worms, we are fre- quently asked, "What can be expected in another year?" These outbreaks of serious insect pests are a result of the breaking down of one or more of the restraining bonds which Nature uses in keeping such pests under control. Some of the factors which tend to restrict the population of insects are climate, bird population, and the presence or absence of insect parasites and predators. Outbreaks of this kind are not confined to species of the insect world alone and neither are they confined to the animal kingdom. The standard dictionary defines an outbreak as "a sudden and violent breaking forth of something that has been pent up or restrained." This defini- tion seems particularly apt for describing the biological meaning of the word, because it implies that all Nature is in a condition of re- straint and that an outbreak is something abnormal, due to the break- ing of one or more restraining factors. Usually, an insect will become very abundant, and if it is a native insect, it will suddenly disappear the year following a serious outbreak. The reason for this may be attributed to any one of a number of factors, including the prevalence of parasites and predators, unfavorable weather conditions, or an un- usual abundance of birds, mammals, reptiles and other forms of ani- mal life which feed upon these insects. No stage in the development of an insect is free from the attack of these predators and parasites. Even though the eggs of the insect are generally very small objects, they nevertheless have both their predacious and parasitic enemies. No matter how carefully they are hidden away, some of them are al- most certain to be found and destroyed. The larvae of defoliating insects and other insects on the surface of plants, because of their comparatively exposed position, are attacked by a host of enemies too numerous to mention. When the larvae drop to the ground, either accidentally or, as many do, to prepare for the pupal stage, they ex- pose themselves to attack of such predators as mice and skunks, which are very fond of insect food and feed ravenously upon any larvae they find. Ants also frequently feed on smaller larvae. While the insects usually seek secluded spots for pupation, many spin cocoons to protect themselves during this quiescent period, but careful as they may be to hide or protect themselves, many of them will be found and killed. Were it not for the fact that numerous species of insects and higher animals destroy large numbers of both the adult and the young larvae of the Colorado Potato Beetle, this pest would be much more abundant than it already is. In addition to this destruction by other insects, of which between 30 and 40 species have been observed to actually prey upon the pest, the bobwhite or quail, robin, crow and several other birds either pick the beetles from the vines-or dig
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