HETEROMORPHA. 



361 



{Mantispa, the remarkable form Sisyra which is parasitic on Spongilla), while 

 others have a short and more compact body {Myrmclcon). We find here a rare 

 phenomenon, the substitution in the imago of biting mouth-parts for the 

 sucking mouth-parts of the larva, which also occurs in the Dytiscidae among 

 the Coleoptera. 



The pupa is essentially quiescent and free-limbed ; in the Megaloptera it lies 

 enclosed in a coarse-meshed, rounded cocoon. In some forms, however, immedi- 

 ately before changing into the imaginal form, it becomes capable of locomotion 

 and wanders about before casting the pupal skin. In this condition we find a 

 transition to the metamorphosis of the Paurometabola with nymphs capable of 

 movement. 



Panorpatae. The larvae are eruciform and live beneath moss or underground. 

 The head is heart-shaped and the mouth-parts strong and adapted for biting. 

 There may be eight pairs of ventral feet (on the 

 first eight abdominal segments). At the end of 

 the abdomen there is the rudiment of a pair of 

 anal forceps which recalls that of the Forficulidae. 

 These larvae are distinguished from similarly-shaped 

 Lepidopteran and Hymenopteran larvae by the 

 possession of compound eyes composed of closely 

 crowded ocelli. 



Trichoptera. The Phryganeid larvae live chiefly 

 in water in cases constructed by them out of foreign 

 bodies (stones, parts of plants, snail-shells) ; these 

 are in some cases attached to stones. In appearance 

 (Fig. 179) they resemble the Coleopteran larvae. 

 They have three pairs of long thoracic limbs, and 

 at the end of the abdomen a pair of processes beset 

 with hooks (h). At the sides of the abdomen (and 

 of the meso- and meta-thorax) tracheal gills (k) are 

 found in the form of tubes or tufts. The pupa is 

 free-limbed ; the pupal stage is passed through 

 within the larval case after another envelope has 

 been spun within it. Before the imago emerges, 

 the pupa becomes capable of locomotion, leaves 

 the pupal envelope and creeps on to dry land, where the transformation takes 

 place. 



Lepidoptera. The larvae here all agree in appearance and take the form of 

 caterpillars (eruciform). Most of them live on land ; only a few Pyralidac 

 spend their larval life in water. In these latter, tubular tracheal gills may 

 develop (Paraponyx; Acentropus, Hydrocampa, and Cataclysta, on the contrary, 

 are devoid of true tracheal gills). The most anterior of the thirteen externally 

 recognisable rings of the body represents the cephalic complex of segments. It 

 carries the usually three-jointed, short antennae and the biting mouth-parts. 

 A line running in the median plane, and known as the fork-line, corresponds 

 to the growth-suture of the cephalic lobes. On the two sides of the head are 

 found six (less frequently five) ocelli arranged in a semicircle. The three 

 thoracic rings which follow after the head resemble in form the abdominal rings. 

 The first pair of stigmata belongs to the pro-thorax, the eight subsequent 

 ones to the first eight abdominal segments. The limbs are rarely altogether 

 wanting (Microptcryx among the Tincidae) ; in other cases they are vestigial 



Fig. 179.— Larva of Phry- 

 ganea fusca (after Pictet). 

 h, grasping hooks ; k, tra- 

 cheal gills. 



