STATE HORTICULTURAL SOCIETY. 



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the care of their fledglings is said to require may account for the small 

 number of adult insects now destroyed. The old birds have, perhaps, 

 simply swallowed, once in a while, a mouthful of the food they were 

 gathering for their little ones. 



This is the point, however, at which there is introduced into this 

 calculation the element of uncertainty attaching to individual judgment 

 and opinion. Up to this point results should be almost absolutely 

 accurate and certain. Concerning the kinds of food in birds* stomachs 

 and the relative amounts of each kind there is but little chance for error 

 if the investigator is competent and careful. When we come to consider 

 the relative values of different groups of insects, however, or of insects 

 of various sorts on the one hand and certain fruits on the other, we have 

 before us a problem not to be accurately determined in the present state 

 of entomological science, and in fact not accurately determinable, no 

 matter how full our knowledge of insect habits may become. While the 

 fruits have a market price, insects are a class of property which has never 

 been put upon the market, and whose nominal value, positive or negative, 

 depends on the individual knowledge, judgment, opinion, prejudice or 

 notion of the holder. In fact, scarcely a single species is so fully known, 

 with regard to its habits, its distribution, its history, its numbers, its rate 

 of increase, its natural enemies and the whole complex net-work of its 

 relations, that even the most intelligent entomologist can more than guess 

 as shrewdly as possible at its economical value stated in standard 

 currency. The means I have taken to insure as nearly correct an idea of 

 this difficult matter as I could have already been described to you ; but 

 the practical conclusion is that no bird should be condemned to death 

 because of a slight percentage against him. A very decided preponder- 

 ance, one way or the other, alone can justify a positive conclusion 

 respecting the real value of a species. 



Taking up the July record, we find the scale trembling in the 

 balance. The caterpillars eaten by the fourteen birds studied in this 

 month have fallen to three-and-one-half per cent, of their food, the 

 injurious beetles to two per cent., the cethoptera to four-and-one-half per 

 cent., while six-and-one-half per cent, was predaceous beetles, and one 

 per cent, spiders — seven-and-one-half per cent, of beneficial insects 

 against ten per cent, of injurious ones — taking the insect-food alone. But 

 a beneficial insect is far more beneficial than an injurious one is injurious, 

 because each perdaceous insect destroys, as a rule, a number of herbivo- 

 rous ones, so that these fourteen robins undoubtedly did much more 

 harm in destroying their seven-and-a-half per cent, of carnivorous beetles 

 than they did good in eating their ten per cent, of plant-eaters ; and 

 when we reach the bottom of the table and find the paper black with the 

 fruit percentages — raspberries, blackberries and currants running up a 

 total of seventy-seven per cent, of the food — even the most devoted 

 friend of the robin must admit that, if these foorteen were fair examples, 

 the robin is a nuisance in July. If his insects were all injurious we 

 could easily condone his offenses in the fruit-field, but his taste for 

 Carabidse condemns him. 



