THE MYCETOPHILIDA:. 93 
although some good work has been done recently on the Continent, 
especially in Russia. Verrall has not worked this family yet, so the 
British list is far from complete ; nevertheless, forty genera and about 
160 species are recorded, and many reputed. Many of the species 
described by Walker must be eradicated, as in all the other families, 
with the exception of the Dolichopodide. 
Few insects are more abundant than the “fungus gnat,” but their 
appearance is so extremely erratic that one may go a whole year and 
find none, then hundreds may suddenly appear. They seem to have 
been first discovered in the Purbeckian Period, and many genera 
have been obtained from these Mesozoic beds, including P/atyura, 
Sciophila and Macrocera (vide Brodie’s “ Fossil Insects”), from the 
lower Purbecks of Wilts and Hants. From the Solenhofen States 
Germar* describes a Sciara, S. prisca, and one also by Giebel.+ 
The three genera figured by Brodie are given by Giebel as new 
genera, viz., Adonia, Sama, and Thimna respectively. Besides these 
Westwood also figures an obscure species referred to the extinct 
genus Z/iras. When we come to the Tertiary Period we find large 
numbers of these “gnats,” which are represented by the genera 
Zygoneura, Mycetophila, Leia, Sciara, Sciophila, Sciobia, Platyura, 
Macrocera, Heterotricha, Dianepsia, Mycetobia, Aclada, Diadoctdia, 
Boletophila, Cordyla, Brachypeza, Trichonta, Loletina, Gnoriste,t 
and an extinct genus Sackenia; more than 280 species have been 
found, and from widely separate areas, mostly from the ambers of the 
Continent and from America, the rock species being few compared 
to the amber. 
Their range in “me is seen to be fairly wide, as also is their distri- 
bution in space, for the fungus gnats appear in most parts of the 
globe, from Scandinavia into the tropics. They pass into the Arctic 
circle, cold seeming to have no influence on them. For some time 
I kept the pupz of some J/ycef/ophilide in a temperature of 30°, the 
effects of the cold only retarding the development a few days, and 
in no ways injuring the species. In England several species may be 
taken in the middle of winter. 
The habitat of the imagos is generally amongst the grass and in 
hothouses, where they may sometimes be taken in great numbers on 
the glass. They also often appear in great numbers on windows in 
houses, and I have noticed this especially during the autumn. One 
of the most notable points in the habits of these gnats is the peculiar 
* Germar, ‘ Nova Acta,’ Ac. of Leo. Ch. of Austria, 1839, xix. 2, S, 189-222. 
+ Fauna der Vorwelt. Giebel. 
t Edin. New Phil. Journal, 1829, pl. vi., figs. 8, 9. 
