October, '15] BISHOPP-LAAKE: WOOL MAGGOTS OF SHEEP 



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Some wool maggot infestations take place in western Texas during 

 mid-summer and early fall, especially after the wool begins to get 

 fairly long following the spring shearing. It is thought that Lucilia 

 sericata is probably mostly concerned in these attacks although speci- 

 mens have not been reared. Phormia is entirely absent or very 

 scarce during mid-summer in Texas as will be discussed later, hence it 

 could not be the culprit in this instance. 



Seasonal History of Phormia regina 



This species is widely distributed in the United States. It shows 

 considerable differences in seasonal history in different sections of 

 the country. In the Southern States the fly is active throughout 

 the winter, although it may disappear for a few days during cold 

 periods. It usually reaches its greatest abundance in the early spring, 

 diminishing as hot Aveather comes on. During hot, dry seasons, in 

 particular, the adults are not to be found in nature during June, 

 July and August, although at Dallas, Texas, we have succeeded in 

 keeping them breeding in cages throughout the summer. In the 

 northern part of the country the fly is, of course, absent during the 

 coldest weather, but is to be found in large numbers during the spring 

 and fall, and in the extreme north is abundant throughout the summer. 

 At Dallas, Texas, we have kept the species breeding throughout the 

 winter, and it is not uncommon to find carcasses in nature which are 

 literally swarming with maggots of this species during mid-winter. 

 During the coolest weather the development is materially retarded, 

 especially in the pupal stage. It is therefore most probable that in 

 northern latitudes the insect passes the winter in the soil either in the 

 pupal or pre-pupal condition. 



Some rather interesting observations on the wintering of P. regina 

 as compared with Lucilia sericata and other flies, including the screw- 

 worm fly, Chrysomyia macellaria, were made on material collected on 

 carcasses or butchers' offal in the autumn of 1914. One large lot of 

 larvae collected on offal on October 28, 1914, was fed on meat placed 

 on sand at the laboratory in Dallas. Many were migrating during 

 the nights of October 29 and 30 and many had pupated November 2. 

 P. regina and C. macellaria began emerging November 14. Emergence 

 in large numbers continued till the end of the month when adults of 

 C. macellaria became few, P. regina continued to appear in good num- 

 ber till December 9, when emergence ceased entirely. On this date 

 adults of Lucilia sericata began to appear, but all emergence stopped 

 during the cold weather, until February 8, when L. sericata again 

 began emerging and continued to appear more or less regularly up 

 to^ April 15. The maximum emergence of L. sericata occurred about 



