SCIARA. 121 



A special peculiarity of the larvae of more than one species of 

 Sciara, is the habit of forming long processions, consisting of 

 many thousand individuals. The column is sometimes one to t\vo 

 inches in breadth and several feet long, the creatures progressing 

 by those behind climbing over the bodies of their companions in 

 front and thus working their advance forwards, the larvse beiL' 

 covered with a glutinous substance. 



Fig. 10. Sciara. 



Fig. 11. 

 Larva (a) and pupa (b) of Sciara. 



From this habit they are known in Germany as the "Heer- 

 worm," or " army worm." The object of these migrations is not 

 exactly known, as they take place only when the larvae are nearly 

 fully grown, and the suggestion that it is in search of new feeding 

 grounds has been contested. S. militaris is the European species 

 in which this peculiar habit has been most frequently observed. 



Some species form a rough silky cocoon, others an earthy one 

 in which to pupate. 



One American species, S. americana, "Wied., is known as the 

 " yellow fever fly," but there is probably no connection between 

 the insect and the disease. S. inconstans, Fitch, has been found 

 in decaying apples in the Mammoth Caves of Kentucky, Hine 

 saying that the larva bores into the stems of carnations. $. puli- 

 caria, Mg., a common European species, has been bred byDahlbom 

 from rotting galls on Salix pentandra, whilst Giraud bred 

 S. giraudii from field mushrooms in Europe. 



In endeavouring to classify the species of Sciara much difficulty 

 is met with owing to the remarkably close general resemblance 

 that they exhibit one to another. 



