12 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 



occupy twice tliat time. Taking the whole season through, however, 

 the time from the egg of one generation to that of another will average 

 about one month.^® 



TIME OF YEAR WHEN THE FIRST WORMS APPEAR. 



Until the Cotton Worm investigation was begun, our knowledge as 

 to the earliest api)earance of the worms was not only vague, but mis- 

 leading. The statement emphasized by Mr. Grote in the pai)er ah^eady 

 referred to, namely, that the worm does not appear earlier than the latter 

 part of June in the central portion of the cotton belt of Alabama and 

 Georgia, very fairly echoes the prevailing popular belief on the subject; 

 yet careful investigation shows the statement to be essentially erroneous. 

 The date of earliest ai)pearance varies with location, and largely with 

 the curves of isochimal lines; ^^ it also differs somewhat in difi'erent years 

 in the same location, according as the season may be late or early ; and, 

 lastly, it may differ to some extent in different parts of the same re- 

 stricted locality, worms having been found just hatching in one place 

 when, only a few miles distant, others were found nearly full grown. 



While these modifying circumstances complicate consideration of the 

 subject, it is easy to arrive at definite results by taking as a basis obser- 

 vations made at a few particular points during the year. Hence we 

 felt the importance of having such observations made during the spring 

 of 1879 in South Texas and South Alabama at those places where the 

 worm was reported to have appeared earliest in past years. As a 

 result, the fact was fully established that the first worms of the season 

 may, and do, in ordinary years, hatch from the middle of April to the 

 middle of May in the southern portion of the cotton belt. And, more- 

 over, all the facts showed that this season was a late one, for April 

 frosts retarded the starting of cotton in those very sections of Alabama 

 where the worms were first found ; while it is the unanimous opinion of 

 planters in South Texas, where the worms were first noticed, that cotton 

 was from two to three weeks later in 1879 than usual. Therefore, when 

 in the si)ring of 1882 we found the worms of all sizes on rattoon cotton 

 during the latter part of March, in South Georgia and Florida, we were 

 not surprised, although this was fully six weeks earlier than they had 

 ever before been noticed or recorded.^^ 



The first worms are always comi:>aratively few in number and in iso- 

 lated spots. They are, therefore, easily overlooked by all who do not 

 take particular pains to search for them. From such spots as centers 

 the worms multiply and spread in subsequent generations, with greater 

 or less rapidity, according as the conditions are favorable or otherwise. 

 Such increase and spread may be confined to some part of a given county 

 until the cotton is nearly ruined before the cotton in the rest of the 

 county is affected. The worms will then first appear in the remainder 

 much more suddenly and numerously than they did in the former, the 

 parent moths migrating thereto in bevies. As a rule, however, the 

 spread in the southern portion of the belt is gradual and the worm in 



