474 DIPTERA 



a low temperature ; it has been said that they may be seen 

 on the wing in the depth of winter when the temperature is 

 below freezing, but it is pretty certain that the spots chosen by 

 the Insects are above that temperature, and Eaton states that the 

 usual temperature during their evolutions is about 40° or 45° 

 Fahr. They often appear in the damp conditions of a. thaw 

 when much snow is on the ground. T. simonyi was found at an 

 elevation of 9000 feet in the Tyrol, crawling at a temperature 

 below the freezing-point, when the ground was deeply covered with 

 snow. T. regelationis occurs commonly in mines even when they 

 are 500 feet or more deep. The most extraordinary of the 

 Limnobiinae is the genus Chionea, the species of which are totally 

 destitute of wings and require a low temperature. C. araneoides 

 inhabits parts of northern Europe, but descends as far south as 

 the mountains near Vienna ; it is usually said to be only really 

 active in the depth of winter and on the surface of the snow. 

 More recently, however, a large number of specimens were found 

 by Professor Thomas in the month of October in his garden in 

 Thuriugia ; they were caught in little pit-falls constructed to 

 entrap snails. The larva of this Insect is one of the interesting 

 forms that display the transition from a condition with spiracles 

 at the sides of the body to one where there is only a pair at the 

 posterior extremity. 



A very peculiar Fly, in which the wings are reduced to mere 

 slips, Halirytus am2)hihms, was discovered by Eaton in Kerguelen 

 Land, where it is habitually covered by the rising tide. Though 

 placed in Tipulidae, it is probably a Chironomid. 



The group Cylindrotomina is considered by Osten Sacken ^ to 

 be to some extent a primitive one having relationship with the 

 Tipulinae ; it was, he says, represented by numerous species in 

 North America during the Oligocene period. It is of great 

 interest on account of the larvae, which are in several respects 

 similar to caterpillars of Lepidoptera. The larva of Cylindrotoma 

 distincta lives upon the leaves of plants — Anemone, Viola, 

 Stellaria — almost like a caterpillar ; it is green with a crest 

 along the back consisting of a row of fleshy processes. Though 

 this fly is found in Britain the larva has apparently not been 

 observed here. The life-history of Phalacrocera replicata has 

 been recently published by Miall and Shelford.- The larva eats 



1 Tr. ml. Hoc. London, 1897, p. 362. - Tr. cut. Sue. London, T897, pp. 343-361. 



