70 PLANT-BUGS INJURIOUS TO COTTON BOLLS. 



instance is no argument against the effectiveness of the operation. 

 Moreover, it will be shown that the advantages derived from the 

 removal of a third or even a fifth of the insects from the plants amply 

 repaid the expenditure. 



An exact count gave approximately 775 bugs to a pint; this was 

 used as a basis for estimating the number of conchuelas picked. The 

 average number of bugs picked per boy per hour varied, according 

 to the abundance of the insects and the efficiency of the supervision, 

 from 8 to 85. As it was not considered advisable to teach the boys 

 to distinguish between even such widely different insects as grass- 

 hoppers and Pentatomid bugs, insects were collected indiscrimi- 

 nately.^ The list of insects found in a lot thus captured on July 12 

 gives an idea of the comparative abundance of the principal con- 

 spicuous and most easily captured insects in a cotton field. Unless 

 otherwise stated the insects in the following list are adults. 



List of insects captured in a hand-picJcing experiment in a cotton field at Tlahualilo, 



Mexico. 



Number. 



Hemiptera 3,753 



Pentatoma ligata Say (conchuela). 



Adults 3, 637 



Nymphs. 75 



Thyanta sp 16 



Pentatoma sayi St^l. (grain bug) 5 



Largus succinctus L 15 



Oncopeltus fasciatus Dall 3 



Lygxus turcicus Fab , 2 



Coleoptera 250 



Epitragus sp 200 



Allorhina nitida L. (fig-bloom beetle) 45 



Eippodamia convergens Guer. (lady-beetle) > 5 



Orthoptera -• 17 



Brachystola magna Gir. (lubber grasshopper) 16 



Gryllus sp. (cricket) 1 



Lepidoptera 4 



Deilephila lineata Fab. (white-lined sphinx) larvae 2 



Estigmene acrsea Dru. (salt-marsh caterpillar) 2 



Hymenoptera 1 



Bomhus sp. (bumblebee) 1 



Total 4, 025 



Cost of Tiand-piclcing.^ — In Table XXXI specific examples are 

 given showing the cost of hand-picking of the conchuela in its rela- 

 tion to the numbers of the insects obtained. 



a In estimates of the number of conchuelas based on bulk at the rate of 775 per pint, 

 due allowance was made for the space occupied by other species of insects. 

 b In referring to cost in Mexico, equivalents in the United States currency are used. 



