PARASITES OF GIPSY-MOTH PUPiE. 



247 



tory as could be expected. The collections of nests from areas II and 

 III on the map (PL XXII) produced the parasite in abundance, and in 

 area I, throughout which it was found the winter before, it was very 

 much more abundant, as will be seen by reference to the tabulated 

 summary of the results of the work for the winter in Table X. 



Table X. — Monodontomerus areas as distributed over its area of dispersion. 1 







Number 

 of brown- 

 tail nests 

 collected. 



Number 



Monodon- 







Number 

 of brown- 

 tail nests 

 collected. 



Number 



Monodon- 



Section. 



Year. 



of Mono- 

 donto- 

 merus 



recovered. 



tomerus 

 per 1,000 

 brown- 

 tail nests. 



Section. 



Year. 



of Mono- 

 donto- 

 merus 

 recovered. 



tomerus 

 per 1,000 

 brown- 

 tail nests. 





f 1908 



5.574 



39 



6 



4 



1910 



1,698 



234 



137 



1 



\ 1909 



2,200 



708 



376 



5 



1910 



701 



215 



305 





I 1910 



1,508 



495 



328 



6 



1910 



2,836 



521 



183 





[ 1908 



947 











7 



1910 



1,050 



260 



246 



2 



\ 1909 



1,107 



124 



112 



8 



1910 



555 



86 



151 





1910 



700 



182 



260 



9 



1910 



825 



538 



652 



3 



/ 1909 

 \ 1910 



770 



34 



49 



10 



1910 



500 



1 



2 



260 



13 



50 



11 



1910 



1,600 



95 



59 



1 Refer to the map (PI. XXII) for the area included in each section. 

 Table Representing the Rapid Multiplication of Monodontomerus in the Field. 



Average of sections 2 and 3 in 1909. . . 

 Average of sections 2 and 3 in 1910. . . 



Brown-tail 

 nests col- 

 lected. 



1,927 



Monodon- 

 tomerus 

 recovered. 



168 

 190 



Monodon- 

 tomerus 

 per 1,000 



brown-tail 

 nests. 



87 

 199 



In 1910 a fairly satisfactory number of the parasites was reared 

 from collections of brown-tail moth cocoons made in the field, but 

 when the gipsy-moth pupse were examined in the field as in 1909, 

 scarcely if any more were found to be parasitized. This was any- 

 thing but encouraging, because it had been expected that parasitism 

 would amount to at least 1 per cent, if the rate of increase which had 

 prevailed up to 1909 had continued. It appeared that the Monodon- 

 tomerus was either inclined to pass over the gipsy-moth pupse in 

 favor of other hosts, or else that its rate of increase had received a 

 sudden check before it was sufficiently abundant to become of aid in 

 the control of the moth. As before, that winter's work was anticipated 

 with interest since its results would be more directly comparable with 

 those of the year before than was that summer's work. 



The collections of winter webs were first made in the territory 

 included within the range of the parasite in the winter of 1909-10 

 (areas I, II, and III), and the fact soon became manifest that instead 

 of increasing it had actually decreased in abundance throughout that 

 territory in the course of the year. It was inexplicable, in view of the 

 unlimited opportunities for increase, and it was, to say the least, 

 discouraging. 



