Page:The Scientific Monthly vol. 3.djvu/393

 NEW JERSEY'S INSECTS

��387

��as scavengers^ these being found principally in the orders Coleoptera and Diptera. Belonging chiefly to the Mallophaga and Diptera, we have only 2.40 per cent, which are injurious to vertebrates, among which however are species closely associated with man and disease. In the Coleoptera, Hymenoptera and Diptera are found most of the pred- atory forms, amounting to 16.97 per cent. These, of course, are en- gaged in feeding upon and destroying those of their kind and others which might be more or less beneficial. The largest percentage, 48.19, consists of insects which injure vegetation and is made up chiefly of species from the Lepidoptera, Coleoptera and Homoptera although some of the other orders are fairly well represented. In the parasitic group, the 12.05 per cent, is found solely in the Hymenoptera and Dip- tera. Classing the scavengers, the poUenizers, the predatory and the parasitic forms together, we have a total of 47.28 per cent., a number which almost equals the percentage of injurious ones. Thus it is seen that almost one half of the species of insects which we have in our midst are engaged in useful activities.

Considering the injurious ones from another viewpoint, namely^ that of destructiveness, it is surprising how small a proportion is de- structive enough to warrant the application of insecticides or remedial measures. The following table (III) gives the total number of species in the seven most important orders and the number and percentage of destructive ones. It must be remembered, of course, that there are numerous other species classed as injurious, but these do not occur in sufficient numbers to make their presence felt or they conflne their at- tentions to imimportant plants and are therefore not included in the list.

TABliB in

��Ord«r

��Coleoptera .... Lepidoptermf.. Hprmenoptera

Diptera.

Heteroptera... Homoptera.... Orthoptera....

��Total No. SpeolM

��3,108

2,120

2,007

1,707

413

607

152

��No. of D«8traoiiTe Speolet

��50 58

9 28

8 28

5

��PeroenUfo of Do- stmctiTe Spoeies

��1.60 2.73 0.44 1.64 1.93 5.52 3.28

��Of the entire number of species listed from New Jersey, 10,530, which includes all orders, only 1.76 per cent, is really destructive. Of the entire number in the seven orders in Table III., only 1.85 per cent, is destructive. As to the individual orders, the Homoptera have the largest percentage and the Hymenoptera the smallest, which is not strange considering the fact that all of the members of the Homoptera are plant feeders, while the Hymenoptera consist of both beneficial

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