August, '16] CORY: COLUMBINE LEAF-MINER 421 



Usually not more than eight to ten larvse can be found in the three 

 lobes of a leaf though in plants under breeding jars, as high as thirty- 

 three larvae have succeeded in reaching the pupal stage in a single 

 leaf. 



General Statement of Seasonal History 



Phytomyza aquilegicc Hardy hibernates in the pupal stage, the first 

 adults appearing during the last of April and the first of May. These 

 deposit eggs about the first of May, These eggs require nearly twice 

 as long for their development as those of succeeding generations. The 

 second generation appears about the 25th of May, completing its life 

 cycle about one month later. From the beginning of the second gen- 

 eration the broods overlap considerably, but a third generation devel- 

 ops about the last of June. From that time on through July and 

 August the parasites are numerous and it is extremely difficult to 

 find any unparasitized larva3. Moreover, it appears that during this 

 time the adults cease to deposit as no new mines have been found 

 during this time. The lack of infestation during the last of July and 

 August may be due to the fact that very few new leaves are produced 

 by the plants at this station after July 15, until the middle of Septem- 

 ber. However, a fourth generation appears about the middle of 

 September and winters in the pupal stage. 



The Egg 



The egg is oblong-oval, slightly larger at one end. It is translucent 

 pale greenish white, sub-glossy and bears no surface markings. Length 

 123. X 235. microns. 



The eggs are deposited in the under side of the leaves with the point 

 sometimes directed almost at 90 degrees to the leaf surface and again 

 they may be pushed into the tissues so far that they lie parallel with 

 the leaf surfaces (Fig. 25a). 



Before copulation or oviposition, the females feed, puncturing the 

 leaves with their ovipositors in hundreds of places. The ovipositor is 

 inserted on the upper side of the leaf and the bod}^ twisted on the 

 ovipositor as an axis until the opening is quite large. The adult then 

 backs away from the incision until the head comes over the opening, 

 when she feeds on the exuding liquid. 



After feeding for a time the adults copulate for a period of 40 to 50 

 minutes. Sometimes a female copulates a second time. They begin 

 egg-laying very soon thereafter. 



The Larva 



The first stage larva is about 650 to 750 microns long when newly 

 hatched. It is translucent and nearly hyaline, though showing some 

 yellow bodies, apparently fat cells. The light brown chitinous mouth- 



