3424 



THE WORM-LIKE ANIMALS 



activity, and scatter over the ground in search of another growing blade of corn. 

 If they fall in with one, they start to creep up it, and mounting ever higher and 

 higher, as the corn grows, ultimately succeed in reaching the summit. They then 



attack the soft grain, bore into it, and 

 form gall-like swellings, in the middle of 

 each of which there is a larval worm. 

 Here the worms quickly develop to normal 

 perfection, and after the females have laid 

 a large quantity of eggs, both they and the 

 males die. Subsequently the eggs hatch, 

 and the larvae, which constitute the 

 powdery substance previously referred to, 

 make their appearance. Somewhat simi- 

 lar diseases are produced in other grains 

 by members of the same family; and the 

 turnip eel {Heterodera) is very destructive 

 to root crops. 



Of the parasitic forms, the genus 

 Rhabdonema has a remarkable course of 

 development, one species (R. nigroveno- 

 sum), which is about three-quarters of an 

 inch in length, living, sometimes in great 

 numbers, in the lungs of frogs. This spe- 

 cies is hermaphroditic, and produces in- 

 numerable young ones, which bore their 

 way from the lungs into the alimentary 

 canal of their host, whence they are ex- 

 pelled with the remains of their food. 

 They then develop in a few days into 

 free-living, separately-sexed individuals, 

 bearing a close resemblance to another 

 free-living worm (Rhabditis) . These in- 

 dividuals breed; the females bear one or 

 two young apiece, and these, after devour- 

 ing their mother's vitals, and making their 

 escape by bursting through the skin of her 

 body, pass through a frog's mouth into 

 its lungs, and become the hermaphrodite 

 adult. Another species (R. strongyloides} 

 is of interest, inasmuch as it is parasitic 

 in man in warm climates. 



Two more remarkable Nematoids may 

 be mentioned, both of which infest in- 

 The first of these, Atradonema gibbosum, is found in numbers in the 



HUMBLEBEE THREADWORM. 



A. Male enlarged; a. natural size. 



B. Female enlarged ; b. natural size. 



C. Brood pouch of female (w ) ; c. natural size. 



sects. 



body cavity of the larval and adult stages of the midge; the completely-formed 



