26 INSECTS INJURIOUS TO SUBTROPICAL FRUITS. 



Table I. — Lenf/th of the egg stage of Heliothrips rubrocinrtus, Washington, D. C, 1912. 



From leaves picked in Florida on April 3 the larvas continued to 

 emerge until April 12, giving a minimum length in this case at Miami 

 of at least nine clays. 



The lengtli of the egg stage was not determined by the writer for 

 Florida. Urich foimd that on the island of Trinidad the eggs hatched 

 for three days after they were picked and freed of the adults, but 

 made no exact determination on the length of incubation. The 

 length of the oo^g stage m Florida wtII be very similar to that of 

 Jisemorrhoidalis, or from 8 days as a minimmn to 16 or 17 days as a 

 maximum as observed by the writer in the greenhouse. 



In the greenhouse a number of experiments were conducted and 

 gave a length of the larval stage of from 8 to 16 days, with average 

 mean temperatures of 68° to 76° F. (See Table 11.) 



Table II. — Length of larval stage of Heliothrips rubrodnctus in greenhouse, Washington, 



D. C, 1912. 



1 Records missing for first foiir days, but would probably not alter the average mean temperatvu^ more 

 than a degree either way. 



In Trinidad the larval period requires six days for development. 

 The temperatures were not stated, but were probably quite high, 

 as the growth was very rapid. In Florida the larval period will 

 probably occupy from 6 to 20 days, depending upon the tempera- 

 tiu"e and humidity. 



Urich found that the prepupal stage required one day and the 

 pupal stage two days for development. During the month of 

 November, with a moderately cool temperature, in a greenhouse, 

 the writer found that the prepupal stage required from one to two 

 days and the pupal stage from two to six days. 



A large number of prepupse, under observation in the greenhouse 

 in April, 1912, were found to requii'e from one to four days for devel- 



