158 



NATURAL HISTORY OF ARTHROPODS. 



FIG. 229. Mantispa interrupta ; 

 the wings not shown iu the 

 lower, side view. 



April the minute larva of the first stage finds its way into the egg-sacs of spiders be- 

 longing to the genera Lycosa and Dolomedes, biting a curved slit, through which it 

 enters into the sack. By the middle of May the larva is still in the first stage, but 



surrounded by dead spiders, showing that it is carnivorous, 

 and diets on young spiders. Before the first moult it some- 

 what resembles a Campodea, but after casting its skin it 

 is maggot-like in appearance, with rudimentary limbs, its 

 motions being like those of a larval bee ; the short, stumpy 

 legs not capable of use. The head is remarkably small, and 

 retracted iinder a fold of the thick second segment, and is 

 transversely oval with an eye-speck on each side, each com- 

 posed of six simple eyes. The jaws (mandibles and maxilla? 

 united) extend straight out, ending in a fine point. On the 

 side are the pointed antennae, which extend beyond the 

 jaws ; the legs are short, thick, obscurely 3-jointed, and situated far apart on the sides. 

 As in the first stage, the larva lies coiled up among the egg-shells and carcasses of the 

 spiders, winding and turning helplessly along. It reaches a length of 7-10 mm. 

 The insect pupates as in Chrysopa and Myrmeleon, the larva first spinning a 

 roundish or oval cocoon within the egg-sack of the spider, where it remains about 

 fourteen days before moulting, the pupa maturing under the larval skin. Pupation 

 occurs in the middle of June, and four weeks after the w T inged insect appears. 



In the metamorphosis of Mantispa there is thus a hypermetamorphosis, i. e., two 

 larval stages. The first stage is Campodectr-formed, and the second is caterpillar-shaped. 

 The transformations of Mantispa appear to give us the key to the mode in which a 

 metamorphosis in the insects was brought about. The larva, born a Campodea-likc 

 form, active, with large, long, four-jointed feet, living a sedentary life in the egg-sac 

 of a spider, before the first moult loses the use of 

 its feet, while the antennae are partly aborted. The 

 fully grown larva is round-bodied, with small, cater- 

 pillar-like feet, and a small, round head. Its external 

 appendages retrograding and retarded, acceleration 

 of growth goes on within, and thus the pupal form 

 is perfected while the larva is full-fed and quiescent ; 

 hence, as a result the pupal stage became a quiescent 

 one, and by inheritance it gradually became a per- 

 manent habit characteristic of Neuroptera, all of 

 which have a complete metamorphosis. This com- 

 plete metamorphosis has probably been inherited by all the orders of metabolic insects, 

 which possibly originated from Neuroptera-like forms, and the imago represents a 

 highly accelerated stage. 



The Ant-lion has always attracted much general interest, from its singular form and 

 peculiar habits. It is the larva of Myrmeleon, and our best known species is Myr- 

 meleon immaculatus. Its habits have been described, as follows, by Mr. Emerton. 



The larva digs a pit-fall, about two inches in diameter and one in depth. In digging 

 its lair the creature begins by making a complete circle, and afterwards throws out the 

 sand from the centre. "In digging it uses its flat head and jaws, which are pushed 

 under several grains of sand and then jerked upwards, throwing their load sometimes 

 as far as six inches, and always far enough to avoid leaving a ridge around the pitfall. 



FlG. 230. Second larva of Mantispa. 



