14 



full growth. During the months of July, August, and September they 

 were stung by this little parasite, which laid its eggs in their bodies; 

 soon afterwards they turned black, the adult parasites issuing from 

 holes cut through the backs of their bodies. The development of the 

 parasite was plainly seen to be very rapid, occupying certainly not 



more than two or three 

 weeks, aud there was 

 therefore a succession of 

 generations, with an in- 

 crease in numbers in 

 geometrical progression, 

 until really the wonder 

 is that a single scale 

 insect escaped. 



The Avriter had under 

 close observation a branch 

 of a large Norway maple 

 tree growing in the Smith- 

 sonian grounds, which in 

 June was fairly plastered 

 with the egg sacs of the 

 Pulvinaria, while in July 

 its leaves were thickly 

 speckled with newly set- 

 tled young; in August he spent an entire morning trying to find a 

 living scale insect, but without exception all which were found had been 

 killed by this important parasite. The little Coccophagus even gained 

 access to the Insectary. Potted maple trees stocked with the scale 

 insects were discovered by them, and the scale was exterminated, 

 although the little trees 

 had been swarming with 

 these scales, and although 

 daily an assistant had 

 picked off and crushed 

 those which, through a 

 change in color, indicated 

 the presence of the para- 

 sitic egg or larva. It is 

 this species probably more 

 than any other which is fig 

 responsible for the fluctu- 

 ations in numbers of the 

 cottony maple scale. As the writer has elsewhere pointed out in speak- 

 ing of parasites of the grain plant-louse, it is probably only through the 

 influence of a dam}) and rainy season, which prevents these active little 

 Chalcidids from flying about to any extent, that the scale is able to over- 

 come the effects of its attacks, enormously prolific as the Pulvinaria is. 



Fig. 8. — Pulvinaria innumerabilin: adult females in position 

 twigs, with egg sacs— natural size (original). 



Pulvinaria innumerabilis: adult female, with fully 

 extruded egg sac showing waxy filaments and eggs as they 

 appear after heing touched — enlarged (original). 



