424 Osten Sacken: on the characters ofthe three divisions oj 



in the MycetopMUdae and their relatives, the section Lestremina. 

 The development of the antennae is large, and, in comparison with 

 the small head, sometinies, we may say, excessive (for instance in 

 some male Cecidomyiae) ; the contrast in this respect with Bibio and 

 Simulmm, with their large heads and small antennae, especially in 

 the male sex, is striking, The distinctive character of the antennae of 

 the Nemocera vera (in common with the N. anomala) consists in the ho- 

 mology of the majority of the joints of the flagellum. But the distinctive 

 character of the antennae of the Nemocera vera, taken separately, 

 is found in the large development of what we may call the sensi- 

 tive hairs, which adorn the antennae, and are arranged, especially 

 in the male sex, in the shape of verticils, pencils, and plumes (the 

 Mycetophüidae form in this case an exception). The legs generally 

 very long, but Aveak, are but little fitted for Walking; structural pe- 

 culiarities, useful for Classification and description, occur only as ex- 

 ceptions (Ceratopogon; hairy fringes in Chironomus etc.). Empo- 

 dia are sometimes present, sometimes not; but there are no pulvilli. 

 In general aspect the true Nemocera are distinguished by their slen- 

 derness and lightness; the elongation of the abdomen in comparison 

 with the thorax is especially noticeable {Psi/choda, which is more 

 thick-set, forms an exception). Their habits are rather crepuscular; 

 they prefer shady places and evening hours. 



The Nemocera vera, in accordance with the structure of their 

 larvae, may be subdivided into two natural sections. 



The Cecidomyidae and MycetopMUdae have peripneustic and 

 terrestrial larvae with eight or nine pairs of Stigmata. The relation- 

 ship of these two families is proved by the occurrence of intermediate 

 forras: the Lestre7nma which, although usually referred to the Ceci- 

 domyidae, are provided with ocelli like the Mycetojjhilidae ; the genus 

 Sciara which, although a Mycetophilid, has lunate eyes, contiguous 

 above, like the Cecidomyidae. 



The second natural section of the Nemocera vera has amphi-, 

 or metapneustic larvae, usually aquatic or subaquatic, but sometimes 

 terrestrial (principally in the Tipulidae, but also among the Chiro- 

 nomidae, for instance, some speeies of Ceratopogon). The affinity 

 between the Culicidae, Chironomidae and Psychodidae is abun- 

 dantly proved by the structure of their heads and antennae, their 

 often lunate eyes, their venation and their sometimes bloodsucking 

 habits. The Tipulidae agree in most respects with these families, 

 although they never have lunate eyes, are never blood-suckers and 

 have a more complete venation, including a discal cell. 



