8 CIRCULAR 295. U.S. DEPARTMENT OF AGRICULTURE 



is started — usually some time between the middle and last of Febru- 

 ary. The second molt is usually completed and the first adult females 

 noted about 2 weeks after development is resumed, or between the 

 first and middle of March, and by the middle of April practically all 

 normally developing females have reached the adult stage, 



The males, which can first be distinguished from the females about 

 the middle of October, continue differentiation from then until, by 

 the middle of November, practically all of them can be distinguished. 

 The males begin transformation to the propupal stage the last of 

 January and to the pupal stage in late February or early March, 

 reaching the adult stage at about the same time that the females are 

 undergoing the final change to adult, or some time in late March or 

 early April. The height of the male emergence period has ranged 

 from the middle of March to the middle of April. Although provided 

 with wings, the males are not strong fliers, and their active life is 

 short — only a day or two at the most. They have been observed 

 fertilizing females shortly after then emergence, frequently visiting 

 one after another in rapid succession. 



Eggs may be observed forming within the bodies of the females 

 shortly after fertilization, or, usually, some time during the first half 

 of April. Thus the life history from egg to egg shows this insect to 

 develop only one generation each year. 



Limbs infested with the obscure scale have been collected from 

 time to time in orchards both north and south of Shreveport. These 

 samples have been examined so that the stage of development of the 

 scale specimens on them might be compared with that of specimens 

 collected in Shreveport orchards at the same time. The variations 

 found have not been great — 2 weeks' difference in development being 

 about the greatest that has been found. These data indicate clearly 

 that this insect has only a single generation each year throughout its 

 present known range. 



NATURAL CONTROL 



Parasites, predators, and diseases, the common natural-control 

 agencies, exert an important influence upon the number of specimens 

 of the obscure scale which are able to develop from crawler to adult. 

 It is difficult to arrive at an accurate estimate of the benefit derived 

 from these agencies, because of the long period through the year in 

 which they work, and because by the end of the year many of the 

 earlier-attacked specimens are destroyed by scavengers, drop off, or 

 are so frayed that they cannot be distinguished from material similarly 

 affected in previous years. 



PARASITES 



Four minute, wasplike parasites have been reared in numbers suffi- 

 cient to indicate their importance in the natural control of the obscure 

 scale. These species, in the order of then importance, are Prospaltella 

 fuscipennis Gir., P. be/iesii How., Physcus varicornis How., said Able/ us 

 clisiocampae Ashm. 4 In addition to the species listed, one or a few 

 specimens of additional probable parasites have been reared but not 

 in sufficient numbers to indicate that they are of importance. Data 

 show that parasites destroyed about 14 percent of the obscure scale 

 during the 1931 season and about 21 percent during the 1932 season 



i Determined by A. B. Gahan of the Bureau cf EDtomology. 



