. Animal biology; Human biology. Parts II & III of First course in biology. Biology. INSECTS 75 are sometimes called the Six-Footed class (Hexapodd). The insects are the only animals that have the body in three divisions. Man, beasts, and birds have only two divisions (head and trunk); worms are not divided. Define the class insecta by the two facts characteristic of them ( possessed by them alone), viz. : Insects are ani- mals with and —. Why would it be ambig- uous to include " hard outer skeleton " in this definition ? To include "bilateral symmetry"? "Segme
. Animal biology; Human biology. Parts II & III of First course in biology. Biology. INSECTS 75 are sometimes called the Six-Footed class (Hexapodd). The insects are the only animals that have the body in three divisions. Man, beasts, and birds have only two divisions (head and trunk); worms are not divided. Define the class insecta by the two facts characteristic of them ( possessed by them alone), viz. : Insects are ani- mals with and —. Why would it be ambig- uous to include " hard outer skeleton " in this definition ? To include "bilateral symmetry"? "Segmented body"? The definition of a class must include all the individuals of the class, and exclude all the animals that do not belong to the class. The leg of an insect (Fig. 125) has five joints (two-short joints, two long, and the foot). Named in order from above, they are (i) the hip (coxa), (2) thigh ring (trochanter), (3) thigh (femur), (4) the shin (tibia), (5) the foot, which has five parts. Which of the five joints of a wasp's leg (Fig. 122) is thickest? Slenderest? Shortest? One joint (which?) of the foot (Fig. 122) is about as long as the other four F]G I26-_FooT OF joints of the foot combined. Is the relative FLY, with climbing length of the joints of the leg the same in Pads- grasshoppers, beetles, etc., as in the wasp (Figs.)? Figure 125 is a diagram of an insect's leg cut lengthwise. The leg consists of thick-walled tubes (o, n) with their ends held together by thin, easy-wrinkling membranes which serve as joints. Thus motion is provided for at the expense of strength. When handling live insects they should never be held by the legs, as the legs come off very easily. Does the joint motion of insects most resemble the motion of hinge joints or ball-and-socket joints? Answer by tests of living insects. There are no muscles in the foot of an insect. The claw is moved by a muscle (m) in the thigh with which it is connected by the long tendon (2, s, t, v). In whic
Size: 1911px × 1308px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1910
