LIFE HISTORY OF THE COMMON SQUASH BUG. 25 



were obtained July 31, from nymphs taken from the field while in the 

 fifth stage. This lot had completed its life cycle from the hatching of 

 the egg to the emergence of the nymph from the last nymph skin in 

 twenty-eight days, or in exactly four weeks. From tbe lot kept in con- 

 finement, from thirty-two to thirty-four days were required. We may 

 then set the aggregate of its nymph periods down as between four and 

 five weeks for this latitude. The egg period was ten days, which would 

 give thirty-eight as the total ascertained period in days of the complete 

 life cycle. 



The first eggs of the season of 1898 were taken at Marshall Hall, Mel., 

 June 18. The first nymphs hatched June 27. Eggs that were laid 

 June 19 hatched July 1, or in twelve days. As the weather was very 

 hot during several days of this period, the time of first egg-laying in 

 this locality that year may be safely placed at June 13. 



After the first week of August adults of the old generation had 

 practically disappeared, none being found when sought for, yet during 

 the second week a number of egg masses newly laid were observed 

 which must have been deposited by the adult bugs, as none of the 

 many bugs reared in confinement laid eggs, and there is positively no 

 evidence of more than a single generation produced each year. This 

 is the condition in the District of Columbia and northward, and it is not 

 unlikely that the same conditions prevail in the South, notwithstanding 

 a statement which has been made by an entomologist of one of the 

 Southern States that "several successive broods are raised during the 

 season." It is not impossible, however, that an attempt is sometimes 

 made in exceptional seasons like that which has just passed to produce 

 a second generation but there is no possibility of such developing 

 through the fact that there is no food supply, and further because of 

 the frosty weather which always ensues during the latter part of Octo- 

 ber and during the month of November. A single instance of either 

 protracted development or a futile effort to produce a second generation 

 was observed the past year. A nymph in the third stage of its growth 

 was taken on a squash vine October 13 and kept in a considerably 

 warmer indoor atmosphere until November 9, at which time it had 

 reached only the fourth stage of development. It would eventually 

 have perished if it had been left upon the vines where found. 



NATURAL ENEMIES. 



In spite of the somber color of this insect, its quiet and secluded 

 habits, and its offensive odor, it is not without its natural enemies. The 

 majority of predaceous animals, however, including insects, are gener 

 ally believed to avoid it. 



The number of nymphs of this species on our experimental plats the 

 past season being entirely out of proportion to the large number of egg- 

 masses previously observed, the writer became suspicious that some 

 outside agency was at work in depleting the numbers of this insect. 



