To recapitulate : This species has obviously become diffused from a 

 central point of dispersal, Mexico, chiefly in the following three direc- 

 tions: (1) From Texas eastward through the Gulf States and north- 

 ward along the Atlantic seaboard to Long Island; (2) from Texas 

 northward through the Mississippi Valley and thence through the 

 Ohio River region into Ohio; (3) from Mexico into the neighboring 

 States and Territories, and from Lower California into southern Cali- 

 fornia and Nevada. 



The northward migration of the harlequin bug, although not with- 

 out interruption, Avas apparently quite steady until recent years. 

 Beginning with the year 1897, at which time the insect had reached 

 its maximum as a pest in Maryland, Virginia, Delaware, and adjoin- 

 ing States, climatic conditions adverse to its existence developed. 

 These consisted of sudden changes of temperature, such as cold snaps 

 followed by warm spells and the reverse during the winter. As a 

 result this l)ug, with several other forms of southern origin, was killed 

 w^hile hibernating and practically disappeared in the North until, at 

 the date of writing (1908), it is scarcely, if ever, reported as in- 

 jurious from the District of Columbia Tiortlnvard. These conditions 

 were particularly noticeable in the winter of 1898-99.*^ Small scat- 

 tering colonies are, however, occasionally found in this region, chiefly 

 on wild plants, late in the fall. 



LIFE HISTORY. 



In the warm and equable climate of the South where this species 

 is at home it is more or less active throughout the year. Farther 

 northward, however, after the first severe frosts of December it goes 

 into hibernation in tufts of grass or under rubbish at the bases of 

 cabbage stalks or in any convenient j)lace. This takes place chiefly 

 in the adult stage, althougli some nymphs of the last stages remain 

 afield as late as November and December. Doubtless the nymphs 

 .succumb in time to cold, and hence fail to survive the winter.'' The 

 first warm days of February or March, in the Gulf region, oi' of 

 April, farther north, see the bugs appear abroad and beginning to 

 feed. At first wild mustard and other cruciferous weeds are attacked 

 and soon the inse(;ts are ready to reproduce their kind. On these wild 

 plants the eggs are deposited, on end, generally in two more or less 



« See Bui. 22, n, s., Div. Ent., U. S. Dept. Agric, pp. 54, 55. 



* A number of adults and nymphs in the last two stages obtained from Lam- 

 bert's Point, Va., October 21, 1907, were placed in a rearing cage with growing 

 cabbage plants, grass, and similar rubbish to provide means of hibernation. For 

 over a month or until some time in December the insects continued feeding, bnt 

 when examined during the first week of March it was found that all had suc- 

 cumbed to the severe cold weather of February. 

 [Cir. 103] 



