Notes on the Green Bug in Texas. 277 



THE SPOTTED LADYBIRD-BEETLE AS AN ENEMY OF 



THE GREEN BUG, AND A STATEMENT OF 



FIELD CONDITIONS. 



Comprising- a part of the investigation experiments were 

 begun in July for the purpose of determining the efficiency of 

 the spotted ladybird beetle {Megilla maculata De G.) as an 

 enemy of the green bug. This ladybird which together with its 

 associated relatives was more ordinarily but less becomingly 

 called ladybug by the farmers, appeared to be the most common 

 and consequently the best known of its family occurring in 

 northern Texas. In the country about Piano the adults of this 

 species alone, without considering the larvae, were- the most 

 conspicuous and abundant of all beneficial insects observed 

 in the wheat and oats fields during May and June. 



The other inimical insects were chiefly Scijmnus loeivii Muls., 

 Hippodamia convergens Guer., and Chrysopa plorahuyida Fitch. 

 Previously the aphid parasite, now known as Aphidius testa- 

 ceipes Cress. (Formerly Lysiphlebus tritici Ashm.), being 

 reported by Prof. C. E. Sanborn, who had watched the fields 

 from the start of the outbreak, had played an important part 

 in reducing the green bug to the point of extermination, and 

 then had vanished suddenly itself. Its absence, therefore, 

 precluded it from further consideration. Besides, owing to 

 the scarcity of the green bug, which at last completely dis- 

 appeared soon after the middle of June from under observa- 

 tion in the fields, the stock for experimental purposes was 

 necessarily bred on oats and wheat seedlings in pots and cages'. 

 However, other grain aphides, principally Siphocoryne avense 

 Fabr., survived sporadically in the fields in spite of the differ- 

 ent ladybirds and associated predators, and subsided upon the 

 plants until their nourishment failed, whereupon a marked 

 development and dispersion of winged migrants took place. 



In the expectation that a similar development would occur 

 ^\'ith the green bug, so it might be enabled to reach other host 

 plants for the summer, preparations were made for subjecting 

 a number to the same field conditions by stocking tight muslin- 

 covered field cages with introduced colonies. But as the grain 

 plants had already begun to dry and turn yellow at the time, 

 the bugs failed to thrive long enough for any noticeable change 

 to take efi'ect. If the experiment had been started earlier, 

 while the field plants were succulent, so as to have allowed the 



