PHILiENUS SPUMARIUS. 85 



XXIV., fig. Ic). The soft parts of the larvae are well 

 suited for the study of the viscera. 



Changes of skin occur several times before passing 

 into the pupa, and these are made within the spume. 



As P. spwuayia can blow as many as seventeen 

 bubbles in the course of half a minute, the air probably 

 is drawn into the spiracles, and then forced from the 

 anal opening through the tenacious liquid. 



After remaining on the herbage for a week or more, 

 the frothy mass thickens from evaporation of the 

 watery particles, and then it forms a cavity, within 

 which the final transformation is effected. 



Sometimes the larva becomes the prey of a small 

 Hymenopterous parasite. I have met with two in- 

 stances of such, where the globular mass of spume 

 has dried into reticulated threads, and formed a net- 

 work over the dry carcase of the pupa (see Plate 

 XXIII., fig. 2h). 



Mr. Darwin attributed little to the effect of climate 

 in modifying species. He urged that species spread 

 over a wide range show a greater variability than those 

 scattered over a limited range. It is worthy of remark 

 that this aphrophorous habit is common to the genus 

 over many parts of the world. According to Bennett 

 Aplirophora gondotii, a Madagascar species, emits a large 

 quantity of clear watery liquid, which drops freely from 

 the trees even in the hottest time of the day. Ants are 

 said to resort to these insects for moisture, but a similar 

 habit has not been observed by me in English ants. 



If we ignore climatal action, it seems to increase our 

 difficulty in explaining the extreme variability of 

 ridJmmis spumariu. No less than eighteen clear varieties 

 are noted by Sahlberg, thirteen of which are sufficiently 

 marked to induce authors to give them distinct names. 

 As before stated, but four only of these are now con- 

 sidered to be true species. It may be so ; yet form, 

 proportion, colour, and markings are so different 

 amongst them, that, until more is known of their life- 

 history, some may liesitate certainly to decide for or 

 against their specific value. 



