110 Zoologica: N. Y. Zoological Society [III; 3 



jids are described as attaching themselves by the last segment to 

 the substratum, and pushing back the larval skin to the tip of 

 the abdomen which remains fixed to the exuvium. In Oryzse- 

 [jhilus surinamensis the larva before pupating makes a rude 

 cocoon by agglutinating particles of food or detritus with an 

 oral secretion, but I have seen no circumstantial account of the 

 process which may be of considerable interest in connection with 

 the cocoon-building of Coccidotrophiis. The Cucujus larva also 

 makes a rude cocoon (see p. 177). 



The construction of a substantial cocoon by the larvae of 

 the social Silvanids would seem to be necessary, because a nude 

 pupa, even if attached to the petiolar wall by its anal end, would 

 be exposed to injury by the numerous beetles and larvse moving 

 about in the narrow cavity. But the way in which the cocoon is 

 constructed is, to say the least, very unusual. So far as known, 

 the larvae of Coleoptera and other insects, when engaged in 

 making such structures, remain in situ and build the cocoon as 

 an envelope around the body, using for the purpose extraneous 

 particles of earth, detritus, wood or frass, or threads of silk 

 spun from the sericteries or more rarely a secretion of the 

 Malpighian tubules, as in ant-lions and certain weevils, as 

 described by Knab (1915a, 1915b) and others, or several secre- 

 tions as described by Bdving for Donacia (1910). The Coccido- 

 trophus larva, however, laboriously collects minute particles of 

 living plant-tissue, mixes them with saliva and builds them up 

 in a very definite manner, repeatedly leaving the structure to 

 go afield for the purpose of collecting the necessary materials. 

 When the cocoon is all but completed the larva enters, and 

 becoming a voluntary prisoner, closes the aperture at the end with 

 materials scraped from the inner surfaces of the walls. I have 

 failed to find in the entomological literature any account of such 

 a method of cocoon-building, which in many particulars resembles 

 the nest-building of certain birds and rodents. 



The only suggestion I can make in regard to the possible 

 origin of this behavior is that it may be derived in some way 

 from the beetle's habit of building up its frass in more or less 

 regular ridges, or welts between the food-grooves or immediately 

 around the entrances to the petioles. I have been unable actually 



