TABANID EGG PARASITE PHANURUS EMERSONI GIRAULT 5 



sand in the bottom. Females have been transferred from one egg 

 mass to another without appreciably interfering with the process of 

 oviposition. 



At Uvalde the total developmental period for the immature stages 

 has ranged from 12 to 19 days, the average being 17.3 days, from 

 oviposition to emergence of the adults. The incubation period of 

 Tabanus hyalinipennis eggs has been from 5 to 9 days, usually 7 to 8 

 days. The immature stages appear to require a certain amount of 

 moisture, since many did not develop in egg masses collected and 

 kept in pill boxes without any moisture during hot dry weather. 



Adult parasites begin to appear in the early summer as soon as 

 the weather has continued hot for some days. The earliest recorded 

 appearance was from eggs collected April 23, 1920, from which 

 adults emerged on May 10. The latest emergence was October 

 1, 1914. 



TABANID EGG COLLECTING AND PARASITE DISSEMINATION 



After the tabanid eggs had been located in great numbers and the 

 egg parasite discovered in the late summer of 1914, some ranchmen 

 about Laguna Crossing, following the suggestion of the writer, col- 

 lected the eggs along the stream for a distance of 14 miles and placed 

 them in tin cans and buckets along the river. It was not possible to 

 determine accurately the quantity of eggs collected by the ranchmen, 

 but it was estimated at approximately 10 to 12 gallons of masses, or 

 20,000.000 to 25,000,000 eggs. This section was the most heavily 

 infested with horseflies of any during 1914. 



During the early part of the season of 1915 it was estimated that 

 there had been a 50 per cent greater decrease in the number of flies 

 in the area where the eggs had been collected than in other similar 

 areas not so treated. Eggs collected at the time of the examinations 

 along this part of the river were more heavily parasitized than at 

 other places, samples averaging 50 per cent or above. 



During July, August, and September, 1915, parasitized eggs were 

 collected along about 40 miles of the Nueces River and distributed 

 in streams over the other parts of the escarpment. One hundred 

 and five distributions of from one-fourth to 1 pint at each place 

 were made, and a total of 52 pints of eggs were used. At the time 

 the distributions were made, samples of egg masses were collected 

 from each place to determine whether the parasite was already 

 present. Parasites were reared from 51 of the 105 collections. They 

 were found over the entire escarpment but were found more gen- 

 erally distributed in the western half. From 1916 to 1926, inclusive, 

 egg masses were collected each year over portions of the area to 

 determine if the parasite was still present. A total of 139 collec- 

 tions have been made and parasites have been reared from 136. 

 They have remained rather well distributed, but the percentage of 

 eggs parasitized has usually been less in the eastern half than in the 

 western half of the area. This indicates that the parasite would 

 be more effective in tabanicl control in areas of light rainfall. 



