INSECT ENEMIES AND THEIR CONTROL 117 



The two sexes of the nematode are shown in Figs. 35 

 and 36. These worms are so minute that it is necessary 

 to use enlarged illustrations in order to show their 

 various features. Fig. 35 represents the mature female, 

 which is nearly pear-shaped and less than a millimeter in 

 length. The body cavity of the female is occupied by 

 eggs and larvae. Fig. 36 shows the slender, threadlike 

 male, which is 1 to 1.5 millimeters in length, with en- 

 larged parts. Scofield, of the U. S. Department of Agri- 

 culture, gives the following life history of the nematode 

 in Circular 91, U. S. Bureau of Plant Industry : 



"The larvae of the gall worm upon hatching from the egg, which 

 hatching sometimes occurs within the body of the parent, ultimately 

 escape from the host plant and live for a period in the surrounding 

 soil. These larvae, although very active, have but little power of 

 progressive locomotion, and the spread of infection from place to 

 place must depend upon the transportation of infested soil or in- 

 fested plants. Soon after emerging from the parent and the tissue 

 of the host plant these larvae seek other roots and bore their way 

 into the plant tissues by means of a spearlike structure, which is 

 protruded from the mouth. They feed upon the cell sap of the host 

 plants. 



'After fertilization takes place the females begin reproduction 

 by forming eggs within the body. These eggs are laid at the rate 

 of from 10 to 15 a day, and it is estimated that one female may lay 

 as many as 500 eggs. After completing the egg-laying process the 

 female dies, the male having died soon after fertilizing the female. 



"The worm lives from one season to the next, either in the egg 

 stage or in the larval stage within the host plant. The life of the 

 individual worm is short (only a few weeks), when temperature 

 and moisture conditions are such as to favor growth.* It is pos- 

 sible, therefore, to greatly reduce the numbers, if not to exterminate 

 the worm entirely, by keeping the infested land free from plants 

 upon which the worm can feed." 



The characteristic root galls of the cucumber, pro- 

 duced by this parasite are shown in Fig. 37, of the 



* Additional information concerning the life history of this parasite, with 

 a list of susceptible plants and details of experiments in controlling the nematode 

 in the southeastern United States, may be found in Bulletin 217 of the Bureau of 

 Plant Industry, entitled "Root-Knot and Its Contrpl," by Dr. Ernest A. Bessey. 



