30 



INSECTS 



fast to some object. Thus it takes con- 

 stant effort in order to remain below the 

 surface. For this reason it is quite nat- 

 ural that they should very often be found 

 floating at the surface where no effort is 

 needed to maintain their position and 

 where an abundant supply of air is acces- 

 sible. 



Another method of securing fresh air, 

 but differing from that of any of the in- 

 sects previously mentioned, is by means 

 of elongated breathing tubes, thus allow- 

 ing the insect to remain submerged and 

 yet secure a fresh supply of air from the 

 surface. This method is used by some 

 predaceous water bugs, as shown in the 

 plate, Ranatra fnsca. As with all of our 

 Predaceous water bugs, which have the 

 elongated respiratory tube at the end of 

 the body, the Water-scorpion has its fore 

 legs adapted for capturing and holding its 

 prey, which consists generally of small 

 fish and insects. The apical part of the 

 fore leg folds back on the basal part 

 which is grooved on its inner face, as a 

 knife blade folds into its handle. As the 

 slender legs of this bug would indicate, 

 it is not an active swimmer, but crawls 

 about slowly. 



Doubtless the best known, to most peo- 

 ple, 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 com- 

 promise 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 men- 

 tioned are ones which throughout life live 

 in water, but a very large number are 

 aquatic only during their larval or imma- 



ture stages. The Mosquito is a good il- 

 lustration 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* sum- 

 marized 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 htmdred eggs. These 

 may hatch in i6 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 

 W'hich 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 larvae of 

 mosquitoes. Every one has noticed that 

 these larva? when not disturbed rest at 

 the surface, but when frightened drop 

 slowdy 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 ten- 

 sion of the surface film which holds the 

 larva up, as the surface tension held up 

 the Water-strider. (. )n the next to the last 

 segment of the Wiggler there is a large 

 breathing tube which reaches to the sur- 

 face when the larva is floating. The food 

 of the larva is said to be decaying vege- 

 table matter. The short pupal period is 

 also passed floating, but it now has two 

 breathing tubes near the points of attach- 

 ment of the wings. WHien ready to trans- 

 form it crawls out onto the pupal skin and 

 dries its wings preparatory to flight. 



Our common mosquitoes belong to 

 three genera, Ciilex, Anopheles and Cor- 

 ethra. The annoyance caused by the irri- 

 tation resulting from the bite is not un- 

 derstood, as no poison gland has been 

 found. The females only of our mosqui- 

 toes are known to suck blood. From re- 

 searches made during the past few years 



