5 INSECTS INJURIOUS TO SUBTROPICAL, FRUITS. 



LIFE CYCLE. 



In ascertaining the lengtii of the life cycle the average lengths 

 of egg, larval, and pupal stages were added together, and to this an 

 additional 3 chiys, which was the usual time from the appearance of 

 the adult female until ovipositing began. The life cycle thus in- 

 cludes the period from egg to egg, or from the time the egg has left 

 the abdomen of the female of one brood until the eggs of the next 

 brood appear. 



Egg stage. — The length of the egg stage was determined by con- 

 fining adult thrips on potted orange plants overnight, then remov- 

 ing all insects and examining the plants twice daily, and counting 

 the larva3 hatched until they cease to appear. The length of the 

 egg stage of 19 eggs during the month of August, 1909, was found 

 to be 2^ days for a minimum and 8 daj^s for a maximum, with an 

 average of 6.2 days. Eggs deposited the latter part of September 

 required from 20 to 24 days for incubation. During May. June, 

 July, and August, 1910. obsei'vations on 45 eggs gave a minimum of 

 5 days, a maximum of 13 daj^s, and an average of 8.1 days for 3 

 months. It is probable that the majority of eggs deposited during 

 ]Ma3^ June, July, and August would require from 6 to 8 days for 

 incubation, while in March, April, September, and October the 

 length of the egg stage would be considerably more. 



Larval stage. — The number of days required for the development 

 of the larva varied from a minimum of 3 days to a maximum of 13 

 days, with an average of 6.06 days for 55 individuals: and a mini- 

 mum of 3 days, a maximum of 13 days, and an average of 7.2 days 

 for 73 individuals during April, May, June, July, and August. The 

 length of the larval stage would probably be extended, similar to the 

 egg stage, during September and October. Two distinct larval 

 stages were observed. The first stage is usually about two-thirds as 

 long as the second, and the larvse more active. 



Pupal stage. — The pupal stage was best observed by keeping larva? 

 in confinement until they pupated. The total length of the pupal 

 instar for 30 individuals, under observation during June and July, 

 1909, varied from 2 to 5 days, with an average of 3.6 days; while 

 287 observations during April to August, 1910, gave a variation of 

 2 to 7 days, with an average of 1.8 days. Two pupal stages were 

 observed, there being a distinct molt from the first to the second 

 stage, which begins with a splitting of the skin from the head back 

 dorsally to about 7 to 9 abdominal segments. The pupae are more 

 active m the first than in the second stage. 



7'otal life cycle. — The life cycle, obtained by adding the aver- 

 age lengths of egg^ larval, and pupal stages, and allowing 3 days 



