14 i The European Elm Scale 



DEATH RATE IN 1907 



"While Oossyparia spuria was abundant and highly injurious in 

 the summer of 1907, it seems likely that the conditions governing their 

 increase were on the whole not so favorable as in the previous summer. 

 We iave spoken of the large numbers of larvae which died within the 

 cocoon of the female and of the high percentage of dead larvae found 

 on some of the leaves (382 in 1000). There were other things 

 which indicated a considerable mortality among these insect pests. 

 Very many males in the spring failed to complete their transforma- 

 tions and died within their cocoons. The elms, on the whole, appeared 

 not quite so seriously infested in this vicinity in 1907 as in 1906 and 

 but few were killed outright, though many were rendered unsightly 

 by dead branches and dull foliage. People living in the vicinity of 

 Carson City stated that their elms had been healthier than usual this 

 summer, but that the elm is always a rather sickly tree in that vicinity 

 owing to the constant presence of the European Elm Scale. 



ONE WAY IN WHICH THE ELM SCALE SPREADS 

 FROM TREE TO TREE 



Late in the summer leaves on infested branches turn prematurely 

 yellow and fall to the ground, carrying down with them no small 

 number of larvae. On September 5th, 1907, it was an easy matter to 

 tell which trees were infested; for on such trees the foliage of the 

 lower limbs was yellow or reddish brown, thin, and falling. Groups 

 of yellow leaves in the midst of foliage otherwise dark green and 



Dec. 14th, 1907. 

 ♦Under all the dead females which I examined today, there were dense 

 masses ol larvae which had died shortly after hatching. In many instances 

 hundreds of them were massed together with the egg-shells. In one such 

 mass I counted 191 dead larvae, in another, there were 280. To a degree 

 this may serve as an Indication of the large number of larvae to which one 

 female gives birth. Many, however, may have escaped. 



Sept. 5th, 1907 

 The color of Gossyparia spuria on infested leaves ranges from lemon- 

 yellow to orange and chocolate brown. Newly hatched and newly moulted 

 larvae are yellow, those more fully grown and not recently moulted are 

 darker. 



Sept 9th, 1907. 

 Twenty-six per cent of the females examined today were still soft and 

 apparently alive. Under the fresher females a few newly hatched larvae 

 could be found occasionally, some few were present here and there on the 

 bark. On the whole the egg-laying season is nearly at an end as the fresh- 

 est females to be found contain very few eggs. 



