20 ANIMAL AGGREGATIONS 



mon aggregation. Mosquito {Culex) larvae in a rain barrel are an 

 example of a synchoropaedium. When larvae of different species are 

 present in the same rain barrel, we have a heterosynchoropaedium. 



e) Similarly, symphagopaedia may result from several groups of 

 the same species laying eggs on the same food material except that 

 here the favorable food rather than the favorable place becomes the 

 integrating factor. This type of aggregation may be illustrated by 

 flesh flies and, according to Deegener, by Drosophila. 



II. Secondary associations may be distinguished from primary as- 

 sociations because they are the result of a coming-together of free 

 individuals rather than their merely remaining together. The classi- 

 fication is based on the integrating factor judged to be most impor- 

 tant. 



1. Sysyngenia arise from the secondary fusion of two or more 

 syngenia. 



2. Sysympaedia consist of fused "children-famihes" and arise when 

 one sympaedium meets with another. Deegener observed such in 

 juvenile spiders of Epeira (1919&). The members of both groups 

 mixed peaceably and gave no sign in their conduct that they were 

 influenced by the foreign spiders; indeed, they did not seem to notice 

 that their membership had been doubled, and new and old alike ag- 

 gregated into one close mass. Another sympaedium was added to 

 these two with similar results, although it was not ascertained 

 whether or not the individuals of a given sympaedium remained for 

 the most part together. 



Two sympaedia of caterpillars of Malacosoma castrense L. are not 

 mixable when the larvae of one sympaedium are in the molting 

 period; otherwise they mix without the caterpillars of the two broods 

 appearing to sense the change in their association. Schulz (1926), 

 in studying the reaction of caterpillars of Vanessa io L., V. urticae L., 

 and Araschnia levana L., found, with the methods he used, no recog- 

 nizable value to rest in the aggregations other than the satisfaction 

 of a social instinct; and this value had lost much of its meaning, 

 since the caterpillars are able to live if isolated, under which condi- 

 ditions they spin small coverings in place of the usual communal 

 nests. They will again take up communal life after an experimental 



