472 DIPTERA CHAP. 



the case that they are much longer in the males than in 

 the females.- Other parts of the body exhibit a peculiar 

 elongation ; in some forms of the male the front of the head 

 may be prolonged into a rostrum. In a few species the 

 head is separated by a great distance from the thorax, the 

 gap being filled by elongate, hard, cervical sclerites ; indeed 

 it is in these Insects that the phenomenon, so rare in Insect- 

 structure, of the elongation of these sclerites and their be- 

 coming a part of the actual external skeleton, reaches its 

 maximum. In several species of Eriocera the male has the 

 antennae of extraordinary length, four or five times as long as 

 the body, and, strange to say, this elongation is accompanied 

 by a reduction in the number of the segments of which the 

 organ is composed, the number being in the male about six, 

 in the female ten, in place of the usual fourteen or sixteen. 

 In Toxorrhina and Mephantomyia the proboscis is as long as 

 the whole body. In other forms the wings become elongated to 

 an unusual extent by means of a basal stalk. It is probable 

 that the elongation of the rostrum may be useful to the Insects. 

 Gosse, 1 indeed, describes Limnobia intermedia as having a rostrum 

 half as long as the body, and as hovering like a Syrphid, but 

 this is a habit so foreign to Tipulidae, that we may be pardoned 

 for suspecting a mistake. The larvae exhibit a great variety of 

 form, some being terrestrial and others aquatic, but the ter- 

 restrial forms seem all to delight in damp situations, such 

 as shaded turf or rotten tree-stems. They are either amphi- 

 pneustic or metapneustic, that is, with a pair of spiracles placed 

 at the posterior extremity of the body ; the aquatic species 

 frequently bear appendages or projections near these spiracles. 

 The pupae in general structure are very like those of Lepidoptera, 

 and have the legs extended straight along the body ; they possess 

 a pair of respiratory processes on the thorax in the form of 

 horns or tubes. 



There are more than 1000 species of these flies known, 

 and many genera. They form three sub-families, which are by 

 some considered distinct families, viz. : Ptychopterinae, Limno- 

 biinae or Tipulidae Brevipalpi, Tipulinae or Tipulidae Longi- 

 palpi. 



The Ptychopterinae are a small group in which the angulate 

 1 A Naturalist's Sojourn in Jamaica, London, 1853, p. 284. 



