2 BULLETIN lOSl, U. S. DEPAETMEXT OF AGRICULTURE. 



DESCRIPTION AND LIFE HISTORY. 



EGG. 



The eggs (PL I. C. V) are of very unusual proportions, being long 

 and slender, somewhat club-shaped or fusiform, with a long cylin- 

 drical stalk. The average length is about 2.5 mm. and the greatest 

 diameter is 0.2 mm. They are inserted into the seed cavity of the 

 fruit from the long ovipositor of the female. The stalk sometimes 

 remains partly in the flesh, although the eggs are never placed 

 there as the young maggots seem unable to survive there. They 

 always occur in clusters, and usually there is only one cluster to a 

 fruit. The cluster consists of from 6 to 20 or more eggs, which are 

 always fastened together by an adhesive substance on the surface 

 of the eggs. One female, according to Knab and Yothers. is capable 

 of laying 103 eggs, all of which are disposed of at about the same 

 time. 



The eggs require from 12 to 11 days to hatch at any time through- 

 out the year. Although the other stages are longer in winter than 

 summer, the ^gg seems not to be affected by climatic changes. This 

 point was determined by cutting open infested fruits at definite 

 intervals after they were stung. Usually an adult wottld oviposit in 

 several fruits on a tree the same evening. It was then possible to 

 cut one of these on each of several successive days until the eggs 

 were found to have hatched. Even in the fruits which had been 

 cut the eggs would complete their development if the halves were 

 placed together, provided they were several days old when first 

 exposed to the light and air. "With freshly laid eggs this was not 

 found to be true. Many attempts were made to rear the eggs arti- 

 jScially after removing them from the fruit but without success. 

 When dissected from the fruit and placed on a piece of leaf or 

 fruit pulp over a plug of wet cotton in a vial inverted in water, 

 as practiced by Back and Pemberton ^ with melon-fly eggs in Hawaii. 

 they failed to develop. Even though the conditions of heat and 

 moisture were apparently the same as in the fruit they did not 

 hatch. 



When ready to liat<;h the eggs split longitudinally along the 

 micropylar half and the maggot escapes, leaving the stalk end intact. 



LARVA. 



The young maggots on hatching from the eggs begin at once to 

 feed on the coating of the seeds. They remain for about the first 

 half of their existence within the seed cavity, feeding on the seed 

 coverings and other fibers there. Many of the seeds become de- 



* Back, E. A., and Pemberton, C. E. The melon fly in Hawaii. U. S. Dept. Agx. Bui. 

 491, p. 18. 1917. 



