June, '13] TOWXSEXD: COTTON SCALE 321 



The first nine of the above are microhymenopterous parasites 

 that attack various diaspine scales; the next three are coccinellid 

 beetles and the next two mites, all predaceous on the scale; the last 

 is a white cottony fungus which attacks the scale. All of these fifteen 

 enemies are very active during the more humid months from June 

 to November, but unlike the scale they are unable to continue highly 

 active during the very dry months from December to May. In a 

 humid region like Panama or Ceylon, these enemies would completely 

 dominate H. minor throughout the j^ear. As it is in Piura, they 

 practically succeed in dominating it by the end of the season of humid 

 nights and mornings, about October or November and sometimes 

 locally much earlier, but a certain small proportion of the young of 

 the scale always escapes their attacks. The few young that escape, 

 being relieved from the activitj^ of their enemies, multiply in ever- 

 increasing ratio during the extremely dry season from December 

 to ]May until the plague assumes nearly the same proportions as the 

 year before. 



Indications suggest the possibility that the enemies of the scale 

 may be slowly gaining on it from year to year in Piura. In 1910 

 it was difficult to find much living scale in November; in 1911 it 

 was noted as very largely dead in October and locally so in Septem- 

 ber; while in 1912 it was found dead over certain considerable areas 

 as early as July and August, and locally so even' in June. Reliance 

 should not, however, be placed on these indications, since a wide 

 allowance must always be made for fluctuations due to factors beyond 

 control, such as variations in climatic conditions and in activitj' of 

 host-plant due to irregularity of water-supply. 



Importation, Liberation and Distribution of Enemies 



The following liberations of material imported into the Piura region 

 from the outside, for the purpose of establishing enemies of H. minor 

 not already occurring there, must be recorded. The scales used as 

 vehicles were all diaspine, and care was exercised to prevent the 

 escape of any species of scale not already present in the region. 



United States — Three shipments of Diaspis pentagona from Wash- 

 ington, D. C. First abandoned in Piura town in August, 1909. 

 Second liberated at Saman in November and December, 1909, some 

 700 microhj^menopterous parasite's by actual count being turned loose 

 in the field as fast as they issued. Third liberated from Paita to Saman 

 in February and March, 1910. 



Lima — Two shipments of five boxes each, containing diaspine scales 

 on Eriobotrya, Dracaena, Magnolia, Opuntia and Rosa. First liberated 



