252 



Pupa. — More slender than pupa of Sciophilinae, and with legs and 

 wings less closely adherent to each other and to thorax. The thoracic 

 respiratory organs and the lateral abdominal spiracles are sessile; in 

 Leia the basal abdominal segment has the spiracles rudimentary. The 

 legs of the two genera are of different lengths. 



HABITS OF LARVAE 



The larvae of most genera of the subfamily are furigivorous, 

 some feeding internally and some externally. Those that feed in the 

 stems or other parts of fungi line their burrows with a slimy sub- 

 stance, while those that feed externally move inside of tube-like slimy 

 threads. 



HABITS OF IMAGINES 



The imagines feed upon nectar and exuding sap of trees. They 

 very frequently feign death when disturbed, and at other times squeeze 

 themselves into very small cracks or openings in an effort to escape 

 capture or injury. 



Keys to Genera 



1. Locomotor spinules indistinguishable or very weak Leia. 



— Locomotor spinules strong, black, forming a conspicuous transverse 



band on each ventral abdominal segment Exechia*. 



PUPAE 



1. Legs quite dissimilar in length, apices of fore tarsi extending to 

 base of fifth segment of abdomen, those of mid pair to apex of 

 sixth, and those of hind pair to base of eighth Leia. 



— Legs of nearly uniform length, terminating at apex of abdomen in 



a slightly concave transverse line Execliia. 



Leia Meigen 



This genus contains a number of common and widely distributed 

 species, which are usually conspicuously marked with black on a red- 

 dish yellow ground-color, and often have distinctly marked wings. 



GENERIC CHARACTERS 



Larva. — Head glossy black, much longer than broad, the posterior 

 margin not excised; antennae very short and fleshy; pellucid spot be- 



*Some species of Mycetophila have locomotor abdominal spinules similar to those 

 of Exechia, as described above. Osten Sacken figures the lateral cephalic sclerites 

 of Mycetophila signata with rounded productions of their inner posterior extremities. 



