Aug. 2i, 1916 Life-History Studies of Cirphis Unipuncta 



801 



For a summary of the data relative to the length of the various stages 

 of Cirphis unipuncta and for the amount of foliage eaten in each instar, 

 the reader is referred to Table I. 1 It will be noticed that the average 

 lengths of the different stages for individuals in the lantern-globe cages 

 and in glass vials were noticeably longer than for individuals reared in 

 the tin boxes. This was not due to the difference in the style of cage, but 

 can be accounted for, as mentioned above, by the fact that the lantern- 

 globe and glass-vial cages were kept on a latticed porch, where the night 

 temperature was much lower than in the laboratory where the tin boxes 

 were kept. It will be noticed that the length of the egg stage is uniform 

 in all cases, as they were kept under like conditions, and the average for 

 153 individuals was between approximately 55^ and 6% days. As Will be 

 noticed, the length of the first five larval instars did not vary greatly one 



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Fig. i. — Diagram of relative amounts of foliage eaten in each larval instar by Cirphis unipuncta. 



from the other, although the amount of foliage eaten in each of these 

 instars was a gradual increase from nearly 0.03 of a square inch for the 

 first instar to over 5 square inches for the fifth instar. The period for 

 the sixth larval instar was noticeably longer than in any of the previous 

 instars, being approximately two and one-half times as long; and the 

 amount of foliage eaten in this instar was nearly seven times as much as 

 in the fifth instar, and more than 80 per cent of all of the foliage eaten 

 during the entire larval period. In other words, the total amount of 

 foliage eaten by the larva during its entire life, an average from 108 indi- 

 viduals, was 41.394 square inches, and the average for the same individ- 

 uals for the sixth instar alone was 34.128 square inches (see Table I and 

 fig. 1). The remarkable voracity of the army worm during its last larval 

 instar explains its sudden appearance in such enormous and destructive 

 numbers only when it is nearly full grown. 



1 Owing to the size of the tables giving complete data for each individual, it is impossible to include them 

 with this paper, but they are on file and may be obtained for reference by anyone interested. 



