June, 1917] Hungerford: Life History of a Boatman. 1]7 



Color. — The brown color is mottled with markings of gray patches 

 regularly arranged. The black fringe of hairs on the thorax at once 

 marks it from the second instar. Fourth longitudinal bands of light 

 blotches mark the definite pattern on the abdomen. 



Structural Peculiarities. — The appearance of the hairs on the 

 thorax as mentioned above and shown in the drawing, PI. IX, fig. 7, is 

 its most distinctive feature. These fringes enmesh the air and pro- 

 vide a reservoir by means of which the nymph is able to carry below 

 an air supply.'' It is this instar that the corixid first manifests much 

 concern regarding its air supply. But from this stage on, frequent 

 adjustments of air store are effected. The metathoracic tibia pos- 

 sesses in all the instars a characteristic depression on the rear margin. 

 This is guarded by hairs and appears to be used in this and later 

 nymphal instars to transfer the air held by the hairs on the wing 

 pads and behind the head shield to other portions of the body. It 

 will be noted that the wing pads, which are covered with a pile of 

 short hairs, do not surpass the metathorax. Compare the drawings 

 of this with those of later instars. 



The fore femur and tibia are stouter than any of the other limbs, 

 especially the tibia, which is more than half as wide as long. 



The mesotarsal claws are still longer than the tarsus itself. The 

 spines on lateral margin of the abdomen are now more numerous than 

 in previous instars, and there are two pairs of short spines on caudal 

 margin of the abdomen. 



Fourth Instar. 



Size. — General measurements: 



Mm. 



Width of head 1.25 



Greatest abdominal width 1.62 



Length of body 3-5 



Specific measurements : 



Femur. Tibia. Tarsus. 



Prothoracic leg .684 



Mesothoracic leg 1.25 .706 .381 



Metathoracic leg 872 .587 1.41 



6 For a full account of respiration of a Corixid see Johannes Hagemann's 

 paper " Beitrage zur Kenntnis von Corixa " in : Zoologischen Jahrbiichern, Bd. 

 30, 1910. (Abt. f. Anat.) 



