Vol. XXli] ENTOMOLOGICAL NEWS. 



455 



c 



In this table the forms compared have been arranged in or- 

 der according to size from the smallest to the largest. The in- 

 crease in total length and in body length is accompanied with 

 increases in the number of crenulations and of spines of the 

 mentum and in the lengths of wing-pads and of female gonapo- 

 physes except in larva No. 3. Miss Butler (1904) has found 

 an increase in the number of distal mental crenulations to take 

 place with increasing age in the larva of Lestes uncatus, while 

 a lack of constant correlation between increased size and in- 

 creased length of wing-pads has been noted by Balfour-Browne 

 (1909, p. 278) and Backhoff (1910, p. 654) for larvae of sev- 

 eral species of European Agrionines. 



A comparison of the last two columns of the table is inter- 

 esting as showing the amount of change which can take place 

 within ten days after a moult. 



General Features of the Larva. 



In spite of their unusual habitat, the larvae of M. modestus 

 show very few differences from the general Agrionine type of 

 larva, the stalked caudal gills of the later stages being one of 

 these. As in most, perhaps all, Zygopterous larvae, the caudal 

 gills may be lost without interfering with growth, development 

 and transformation (PI. XVIII figs. 1-7, PI. XIX fig. 8). Only 

 two features of the larvae seem to be distinct adaptations to 

 their environment, viz., the divided spines of the tarsi and dis- 

 tal ends of the tibiae, and the strongly-curved, sharply-pointed 

 tarsal claws, both classes of structures being apparently of as- 

 sistance in moving up and down the steeply-inclined or verti- 

 cal surfaces of the bromeliad leaves. So little has been done, 

 however, in comparing the minuter details of Odonate larvae 

 that it is not certain that these features are peculiar to Mecisto- 

 gaster. It is also important to note that the larva shows nothing 

 of the hypertrophy of the abdomen which is so striking a char- 

 acteristic of the imago. This great increase in abdominal length 

 is accomplished only at metamorphosis and is clearly brought 

 out by the figures on Plates XVIII and XIX. 



