6 BULLETIN 443, U. S. DEfAETMENT OP AGElCULTURE. 



Upon coming in contact with the tender portions of the human skin, 

 such spines cause at first an intense local irritation or smarting, which 

 later results in a swollen and itching condition of the 

 affected parts, resembling that caused by the sting of a 

 wasp. It is possible that the same thing happens to the 

 mouth of an animal feeding upon this grass, and that 

 after one experience the plants are left untouched. At 

 least the cattle seem to avoid grasses so affected. For 

 this reason many areas of range pas- 

 ture not actually destroyed by the 

 range caterpillar are rendered unfit for 

 grazing purposes. 



LIFE HISTORY. 



During its Hfe (see fig. 4) the range 

 caterpillar passes tlirough four stages — 

 first the egg, then the caterpillar, next 

 the pupal or ''spun-up" stage, and, 

 lastly, that of the moth or parent. 



Egg stage. — ^The eggs (fig. 5) are de- 

 posited by the parent moths (fig. 6) 

 during the months of September, Oc- 

 tober, and November, in cylinder- 



of New Mexico shaped clusters, about the diameter 



range caterpillar of an Ordinary lead pencil, encirchng 



on weed stem. ■, •■ —,, 



Enlarged, (c. grass and weed, stems, ihese egg 



N. Ainsiie.) clustcrs coutaiu from 50 to 175 eggs, 



are pearl-white in color, and from their size and 



position are frequently mistaken for bunches of 



weed seeds. The individual eggs are fig- 6.— The New Mexico 

 very tluck-sheUed and able to with- '^T^JSSL 

 stand the winter weather conditions resting attitude. En- 



in New Mexico. '^'''^- (^'- N- Ainsiie.) 



Caterpillar stage. — The caterpillars (fig. 2) hatch from 

 the eggs as a rule in May or early June, the time de- 

 pending upon moisture conditions. A certain amount 

 of moisture appears to be necessary for hatching the 

 eggs, temperature being of less importance. By late 

 August or during September the caterpillars have com- 



FiG. 7.— The New . ^ . . i i 



Mexico range plctcd their growth and are ready to enter the spun- 



caterpUlar: Pu- ^p" or pupal Stage, 

 pa, side view. i. ± j. o 



Enlarged, (c. Pupal Stage. — In entering its pupal or resting stage 



N. Arnsiie.) (-|^g y-^ ^]^g fuU-growu Caterpillar draws the stems and leaf 



blades of any weed or grass plant together (fig. 8), and inside this 



foundation spins a rough, nethke inclosure or cocoon of yellow silk. 



