1921] Wheeler: Some Social Beetles 109 



in certain ants, c. g., our yellow, hypogaeic species of Lasius, 

 which are able to develop populous colonies mainly, if not exclu- 

 sively, on a diet of honey-dew derived from root-aphids and root- 

 coccids. 



Inasmuch as the larv«, from their very youngest stages, 

 no less than the adult beetles, continually stroke the coccids, the 

 question arises as to whether the habit was first acquired by the 

 larvae, or by the beetles, or whether both instars developed it 

 simultaneously. An answer to this question might, perhaps, be 

 forthcoming if we could determine whether the larva or the 

 adult beetle shows the greater structural adaptation of the 

 antennae and mouthparts to dealing with the coccids. The larvae 

 as I have shown, use both their antennae and maxillae in the 

 process, the adults only the antennae, but although the beetles 

 are able to cover a greater area of the coccid's surface with their 

 antennal clubs, the larger larvae at least, by combining both pairs 

 of organs, can probably produce a stimulus no less intense and 

 effective. The larvae are certainly more alert, restless and 

 inquisitive than the beetles and the mandibles in the youngest 

 stages seem to be very poorly adapted to feeding on the nutri- 

 tive parenchyma. It is therefore quite as probable that the habit 

 of stroking the coccids was first acquired by the young larvae 

 and later continued in the adult as that it originally appeared in 

 the latter and was inherited in earlier and earlier ontogenetic 

 stages till it came to be manifested by the just-hatched larva 

 less than a millimeter in length. As shown by the observations 

 recorded on p. 70 such larvae show an even greater avidity for 

 the honey-dew than the adult beetles. Since the stroking of the 

 female beetle by the male during the courtship is precisely like 

 the stroking of the coccids, we might be tempted to conjecture 

 that the habit had arisen first in the adult as a modification of 

 the sexual appetite, but this is, perhaps, rather far-fetched. 



3. — The Building of the Cocoon. 



The few data I have been able to gather concerning the 

 processes accompanying pupation in the beetles allied to Cocci- 

 dotrophus and Eunausibius are reproduced in Zoologica III, No. 5. 

 The pupating larvae of some Laemophloeids, Silvanids and Cucu- 



