The other little creature is called Sphaero´ma--it has no English name--from the fact that it can roll itself into a ball. It is not difficult to identify, from the fact that all the segments of the pleon are joined into one plate, the hinder margin of which is entire, thus [image]. The garden will afford us a hunting-ground for the last specimen of this group for which we have space--the Woodlice. Enough has been said of the method of looking over and breaking-up I´sopods generally to render detailed description unnecessary. The inner pair of antennae, however, are so small as to be readily overlooked: indeed, on first sight these creatures seem to have but a single pair. Some have, and others have not, the power of rolling themselves into a ball; and, concerning the former, Swammerdam tells the following story:-- ‘One of our maidservants had at one time found a great number of Woodlice in the garden, contracted into round balls ..., and thinking she had found a kind of coral beads, she began to put them one after another on a thread, but it soon happened that these little creatures, which roll themselves up in such a manner only for fear of harm, and appear as if they were dead, being obliged to throw off their mask, resumed their motions. On seeing which, the maidservant was so greatly astonished, that she threw away the Woodlice and the thread, and cried out, and ran away[56].’ CHAPTER VI AQUATIC INSECT LARVAE In this chapter we shall deal with a few aquatic insect larvae. Of these, some are aquatic also in the perfect condition, while others emerge from the pupa stage as aërial insects. It requires no great amount of care to keep these creatures, and some hints on this subject and on collecting are given in the first chapter. The larva of Dytiscus is abundant during the greater part of the year, and is almost sure to be met with by the collector, who will find it an extremely interesting object for examination and study. No other creatures should be put in the same bottle with these larvae; and if there are several of them in one bottle, it is a good plan to put in plenty of pondweed, which will often keep them from attacking each other. When full grown, the Dytiscus larva may attain a length of two inches or rather more. Its colour is dingy brown, and its aspect forbidding enough to justify the uncomplimentary names that have been bestowed upon it--Water-devil and Water-tiger. It certainly rivals the tiger in fierceness, and its method of stealing up to its prey and attacking it from behind led Swammerdam to call it the Sicarius or Assassin Worm.