AND OTHER INJURIOUS INSFXTS OF I907 AND I908. 1 17 



These false caterpillars, differing from the true caterpillars in 

 having from twelve to sixteen fleshy pro-legs in addition to their true 

 six legs, belong to the order Hymenoptera, and the adults of both 

 species which affect willow with us are four-winged flies, not ordi- 

 narily noticed by the casual observer. 



The larva of Cimhex americana, Leach, has a habit of curling up 

 on the leaf as shown in the illustration. It is greenish or pale yellow- 

 ish, with a black stripe down the back. They also have the power, it 

 is said, of ejecting an acid fluid from pores in their skin. When full 

 grown they spin a papery cocoon, changing within to pupae, and 

 emerging later as four-winged flies. The American Cimbex is the 

 biggest Saw Fly we have, resembling somewhat a hornet in size and 

 general appearance. The eggs are laid in the tissue of the leaf. It 

 affects elms and some other trees as well as the willow. 



A second species occurring here is Ptcronns vcntralis, Say; the 

 larva or "caterpillar" of this saw fly being black with yellow spots on 

 its sides. 



Fortunately, both of these insects yield readily to arsenical 

 poisons. A weak combination of Paris green and water, or, better 

 arsenate of lead and water, applied to the leaves will kill them. 



THE ELM CATERPILLAR; MOURNING CLOAK. 



Euvaucssa antiopa Linn. 



Fig. 01. Mourning Cloak Butterfly. Original. 



Early in April and sometimes in March one frequently sees this 

 striking butterfly in sheltered spots in Minnesota groves, for this in- 

 sect hibernates in the adult stage. It is strikingly colored, having wings 



