Doubtless the best known, to most people, of this type of breather, are the Giant water bugs, which accumulate in such large numbers under and in the globes of electric lights. The paired nature of the breathing tube is well shown in the plate. These bugs are powerful swimmers, as is shown by their flattened hind legs. Even young fish are not overlooked by these voracious bugs. A South American kind is much larger than our species, reaching from four to four and one-half inches in length, or about twice the size of our species. The shortness of the air tube suggests that this organ is not used in just the same manner as in the Water-scorpions, and the areas of fine hairs on the under side of the body suggest that these insects may be somewhat of a compromise between those insects which carry air below with them and those which remain submerged, except for the tube which communicates with the air. Most of the insects previously mentioned are ones which throughout life live in water, but a very large number are aquatic only during their larval or immature stages. The Mosquito is a good illustration, of this type. In some of its habits the Mosquito is well known, but this is primarily due to the biting habit of the female. The researches of recent years clearly show that the annoyance from the bite itself, is, in the case of some kinds of Mosquitoes, only a small part of the mischief that they can do. The life history of the Mosquito has been summarized somewhat as follows by Dr. L. O. Howard: The eggs are laid at night, in a boat-shaped mass containing from two hundred to four hundred eggs. These may hatch in 16 hours, the larval stage lasting about a week, and the pupal stage about 24 hours. Thus the entire cycle may be completed in 10 days, under favorable circumstances, but may be greatly delayed by a low temperature. The rapidity with which the complete cycle may be passed through makes it possible for a very large number of broods to occur during a single season. The Wigglers or Wiggle-tails, often so numerous in rain-barrels, are the larvæ of mosquitoes. Every one has noticed that these larvæ when not disturbed rest at the surface, but when frightened drop slowly downward in the water, since they are heavier than this medium, yet they rest at the surface, by means of a rosette of thin plates at the tail end of the body. These act as the hairs on the legs of the Water-strider, and make use of the tension of the surface film which holds the larva up, as the surface tension held up the Water-strider. On the next to the last segment of the Wiggler there is a large breathing tube which reaches to the surface when the larva is floating. The food of the larva is said to be decaying vegetable matter. The short pupal period is also passed floating, but it now has two breathing tubes near the points of attachment of the wings. When ready to transform it crawls out onto the pupal skin and dries its wings preparatory to flight.