38 PLANT-BUGS INJURIOUS TO COTTON BOLLS. 



female brought from the field into the laboratory proved unfertilized; 

 hence this factor should be eliminated from the laboratory records 

 in order to make them comparable with actual field conditions. 



As an illustration of the mechanical prevention of hatching referred 

 to, a conchuela in one instance deposited eggs in two layers, the 

 nymphs in the lower layer of eggs, numbering 20, being of course 

 unable to escape from the shells. This manner of depositing the 

 eggs was evidently due either to interference by other specimens in 

 the cage or to a lack of sufficient leaf-area, both of which conditions 

 are abnormal. Occasionally eggs are deposited, both in the labora- 

 tory and in the field, wrong side up with relation to other eggs of the 

 batch. This also usually results in mechanical prevention of hatching 

 and accounts for the failure to hatch of somewhat less than 1 per cent 

 of the 942 eggs referred to above. Other eggs may fail to hatch 

 owing to the exit hole at the top being abnormally small, as the 

 author has observed to occur in two instances with eggs of the harle- 

 quin cabbage bug (Murgantia Jiistrionica Hahn). The extent of 

 this abnormal condition may not be noticeable, yet sufficient to 

 prevent emergence of the nymph. Still other eggs may be abnormal 

 in the respect that the lid which must be raised to permit the escape 

 of the nymph is too solidly attached to the neck of the egg in 

 proportion to the strength of the insect. 



EFFECT OF LOW TEMPERATURE ON VITALITY. 



An experiment was made to determine the extent to which de- 

 velopment of eggs might be retarded or otherwise affected by low 

 temperature. In this experiment 12 egg-batches comprising 288 

 eggs were used, all of which were deposited between August 27 and 

 September 16 by 8 different females. Each batch of eggs was 

 placed in an ice box within 24 hours after being deposited and kept 

 there until November 2, with the temperature almost invariable and 

 averaging 49° F. Upon examination it was found that the eggs had 

 been entirely destroyed, being shriveled so that there could be no 

 doubt of their condition. It would seem, therefore, that such long- 

 continued low temperatures are fatal to the conchuela in the egg-stage. 



HATCHING. 



As the eggshell is nontransparent, the developing nymph is invisible 

 up to the time of hatching. The stout spine on the egg-burster is 

 directed at the suture between the lid and the neck of the egg at a 

 point opposite the hinge. By pressure from below a split is made 

 along the suture and the pale pinkish head of the nymph surmounted 

 by the egg-burster appears beneath the partially opened lid. The 

 integument of the insect being soft, the emergence is by slow, scarcely 

 perceptible peristaltic movements, the egg-burster sHpping over the 



