10 BULLETIN 491, U. S. DEPARTMENT OF AGRICULTURE. 



an unaffected pistillate flower of any cucurbitaceous host plant grow- 

 ing naturally in the field. No staminate blooms of watermelons, can- 

 taloupes, cucumbers, and certain Chinese marrows have been found, 

 affected, but those of the pumpkin and squash varieties are badly, 

 attacked. An examination of 207 well-developed buds of the male 

 flowers in a field at Waialua during March, 1915, proved each bud 

 to contain the eggs or larvae of the melon fly. Plate VII represents, 

 the early stage of infestation of the male bloom of pumpkins. As the, 

 larva? hatch they feed upon the receptacle and the anthers until the 

 interior is a mass of decay. In the illustrations of Plate VIII are 

 shown three stages in the destruction of the male bloom. In figure 1 

 the larvae have destroyed the anthers and are burrowing about the 

 receptacle; in figure 2 the continued work of the larva 1 and the weight 

 of the bud have caused the latter to break over, while figure 3 repre- 

 sents a very frequent condition after the bud has dropped to the 

 ground, leaving behind a few larvae within the upright flower stalk 

 and carrying others within itself to the ground. When the male 

 bloom is attacked late in its development the corolla unfolds nor- 

 mally, exposing to view unhatched eggs or very j T oung larvae on its 

 inner surface or among the pollen grains. When buds are attacked 

 before they are three-fourths developed they usually are destroyed 

 before they can bloom. Eggs are never deposited in the flower while 

 it is in bloom. 



While injury to the corolla of the female bloom does occur in 

 pumpkins .to a limited extent, the attraction of the unfertilized 

 ovaries is so much greater that this portion of the bloom receives the 

 greater amount of oviposition, and infestations that prevent bloom- 

 ing occur within the ovaries rather than in the corolla and about the 

 style and stigma. The greatest injury to pumpkin, squashes, water- 

 melon, cantaloupes and M onwrdica spp. occurs at this stage, or di- 

 rectly before and after the flower unfolds, and is, to the uninformed, 

 so obscure that the apparent sterility of fields of rankly growing 

 vines is often the cause of discussion. The cross-sections of the bloom 

 of pumpkins in Plate IX illustrate the disastrous result of this 

 attack. In figure 1 the ovary has already been ruined by young larva? 

 before the corolla has opened to expose the stigma for fertilization. 

 In figure 2 is shown a more advanced stage of infestation, but one. 

 occurring before the corolla has entirely withered or lost its color. 

 The three figures on Plate X illustrate the progressive infestation 

 of the pistillate bloom of squash. In these examples the larva 3 have 

 not only attacked the ovaries, but, as in figure 2, have worked their 

 way up into the corolla. Often, in blooms of this type, the work of 

 the larvae, aided by decays started by them and the weight of the 

 upper portion of the bloom, causes the ovaries to break off, as illus- 



