81 



TABLE SHOWING THE LIFE HISTORY OF F(JUR SPEri:\rEXS 

 "I'AXTALA FLAVESCENS" FABR, 



Egg Average 



or Length in No. 1 No. 2 No. 3 No. 4 Average 



Instar mm. for the 



First Three Days Days Days Days Days 



Egg . . 5 5 5 7 51/^ 



1st % —1/2* —V2* —1/2* —1/2* —1/2* 



2nd 1 4 .5 4 3 4 



3rd 11/2 3 '5 7 3 414 



4th 21/3 2 8 6 2 41/2 



•ith 4 3 8 6 3 5 



6th 5 2 5 5 4 4 



7th 6 3 6 3 5 4% 



Sth 8 2 5 6 6 4% 



9th 10 .5 4 9 5 5% 



10th 13 4 9 9 8 71/2 



nth 18 8 13 14 27 ll%t 



12th 24 19 30 30 .. 26i/3t 



Total No. of days 



for growth of nym. 55 98 101 66 80 



Female Female ^Nlale :\Iale 



From the al)ove table it will be seen that the nymphs monlt 

 ten or eleven times ; and that the length of time of incnhation 

 and especially the total nymphal period vary consideraldy in the 

 different indivindals. It will also be noted that the time of the 

 last two or three instars gradually leno-thens, the last, of course, 

 being" the longest, averaging (for the four) more than one-third 

 of the life of the nymph. This long period is due to the great 

 change that takes place during the last stadium, — a change 

 from the nymphal water-inhabiting form, breathing chiefly by 

 means of tracheal gills, to the adult form, breathing altogether 

 by means of tracheae. We may say this period corresponds to 

 the pupal stage of those insects possessing a complete metamor- 

 phosis. During this time many of the organs are greatly 

 changed; and some are even completely reconstructed, such as 

 the respiratory organs, lalu'um, wings, compound eyes, gizzard, 

 etc. 



In the al)ove experiments the ]iym])ha] ])eriod varied from 

 oo to 101 days. It is doubtful if the nymphs complete their 

 growth in nature in so short a time as Xo. 1 did in the above 

 experiment, except in very rare cases, as their food supply is not 

 always close at hand ; and the amount of food, modified doubt- 

 less by climatic conditions, largely determines the rate of growth 



* Less than V2 hr. 

 t For 3. 



