THE CONCHUELA. 49 



subdivisions of the estate to search for any particular insect concern- 

 ing which information may be desired at headquarters. This sys- 

 tem made it possible to obtain accurate information concerning the 

 abundance of the Pentatomid bugs here considered. 



In 1903 the conchuelas were abundant only during the month of 

 July and reached a maximum in numbers about July 20. Their 

 first appearance was in the outlying districts, next to the mesquite, 

 but they soon spread all over the cotton plantation, although they 

 were more abundant in certain parts than in others. The insects 

 disappeared early in August and did not reappear in noticeable 

 abundance during the season, although the cotton plants remained 

 green until October 17, when the first frost was recorded. 



Although a close watch for the insect was maintained during the 

 late spring and early summer of 1904, the first specimen was not taken 

 in the field until July 6. During the following seven days a rapid 

 increase in its numbers was noted, and on July 17 it was observed 

 that a marked decrease had occurred. Nowhere on the plantation 

 were the insects as abundant as in July of the previous year, nor 

 were they so generally distributed. 



On August 31 a personal examination in the cotton fields by the 

 author showed the insects to be very scarce, although in certain 

 sections of the plantation the open cotton bolls with stained and 

 ruined lint gave unmistakable evidence of their greater abundance 

 a few weeks earlier in the season. 



In July, 1905, a detailed numerical study was made, which verifies 

 Mr. Conduit's general observations for the two previous seasons. 

 While the subject of natural enemies is discussed under a separate 

 heading, it is necessary to mention here that the abundance of the 

 conchuela during the season is principally dependent upon the 

 efficiency of its parasitic and predaceous enemies. Egg-laying by 

 the average individual is distributed over such a long period of time 

 that it can hardly be said that the conchuelas naturally appear in 

 broods. However, practically the same effect may be produced 

 locally to a greater or less extent by the action of natural enemies. 

 During the first two weeks of July adults and nymphs in all stages 

 were found in abundance on mesquite in the uncultivated lands 

 surrounding the Tlahualilo Cotton Plantation. The gradual ripen- 

 ing and drying of the beans was evidently causing a migration of 

 the adults in search of food, many finding their way into the cotton 

 fields. Egg-parasitism was acting as a practically complete check 

 on further multiplication in the mesquite. In their search for food 

 the first migrants from the mesquite settled in large numbers in sec- 

 tions of the plantation upon which zoca or seppa (stubble) cotton was 

 growing, and later the migrants showed a preference for the planted 

 22348— Bull. 86—10 4 



