This section is from the book "Commercial Gardening Vol1", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
Although belonging to the same group as the Millipedes or Julus worms the Centipedes (Geophilus subterraneus) are not harmful to crops. On the contrary they are beneficial, inasmuch as they feed on insects, caterpillars, worms, snails, and slugs; they are active and flesh-eating insects, and should be preserved for the good they do.
From what has been said above it may be taken that although nature has sent many insects to plague and worry the cultivator of plants, it has also provided antidotes in the way of birds of all kinds, Ichneumon Flies, Ladybirds, Lacewing Flies, Tiger and other Beetles, Frogs, Toads, and Lizards, Hawkflies, Spiders, and even Slugs, by which they may be kept in check. Unfortunately, with the many poisonous washes now in use it is possible that when applying them the cultivator is slaughtering his friends as well as his enemies. Indeed he is practically not even on speaking terms with his friends, and in many cases would not recognize them as such even if he were to see them. It would be worth while to make a special effort to cultivate colonies of Ladybirds, Ichneumon Flies, Lacewing Flies, and Hawkflies especially, as these by sheer force of numbers would readily suppress the various destructive aphides and caterpillars. When one comes to realize the wonders of the insect world, and how some kinds prey upon others, one is forcibly reminded of the truth of the couplet, that - "Large fleas have little fleas upon their backs to bite 'em, Little fleas have lesser fleas - and so ad infinitum ".
Fig. 162. - Ear-shelled Slug (Testacella halotidea).
Fig. 163. - Epiblemum scenicum (twice natural size).