THE MELON FLY IN HAWAII. 9 



Injury to the foliage and stems. — The very disastrous effects of 

 attack on the foliage is shown in Plate I, figure 1, where the petiole 

 of a watermelon seedling has been tunneled by larvae. Such complete 

 destruction is not usual in older plants after the tissues have hard- 

 ened. Larvae developing in the pipelike petioles of large pumpkin 

 leaves do almost no harm. The manner in which developing runners 

 of watermelon seedlings may be killed back to the crown is illus- 

 trated by Plate XXI, figure 3. As the plants become older the 

 crown becomes so toughened that it withstands attack, the growing 

 tips of the vines, especially those of watermelon and cantaloupe, are 

 seriously attacked, and the larvae developing in the shoot cause its 

 death beyond the point of infestation, as shown in Plate II, and 

 thus bring about a progressive pruning. At the time infestation 

 illustrated in Plate II occurred the growing shoot was so small that 

 the puncture made by the female for her eggs practically cut the 

 shoot and would have produced withering beyond had no further 

 destruction been caused by the larvae developing later. In Plates 

 III and IV may be seen the type of injury to still older watermelon 

 shoots. Note that the young fruit has begun to wither and that the 

 stalk has already turned black and has become flabby to the touch, 

 thus indicating that the interior has been destroyed. This destruc- 

 tion of the interior is shown by the shoot on Plate IV, which has been 

 sectioned to expose the well-grown larvae within. Such pruning back 

 of foliage and shoots appears to occur more often among older canta- 

 loupe vines than among watermelon vines of similar age. In Plate V 

 is given, by way of illustration, a portion of a cantaloupe vine cut in 

 the environs of Honolulu, showing attack in eight places. The field 

 from which this vine was taken bore only small, stunted vines, in 

 spite of the fact that the soil was rich. 



Oviposition in the stems of host plants does not always produce 

 the complete destruction illustrated, since very often the growth of 

 plant tissues may be so rapid that the larvae appear to be killed. 

 Again, they are able to develop locally, reach their full development, 

 and leave the plant without having affected vital injury. Under these 

 conditions, however, the plant may develop an abnormal growth 

 about the feeding larvae. These abnormal developments of the 

 vine have never been observed, in any host plant but the pumpkin 

 and squash, and then reach their fullest development only during wet 

 weather. (See PL VI.) During dry weather, when the vines are 

 tougher, little successful infestation of squash or pumpkin vines 

 occurs. 



Injury to the bloom. — It is difficult during the greater portion of 

 the year in littoral Hawaii, especially on the island of Oahu, to find 



