FIELD BOOK OF INSECTS. 



terminated by three tarsal spines or claws. In warm, 

 sunny weather these triungulins become very active; they 

 run about on the surface of the ground exploring all its 

 cracks, penetrating various spots and burrowing, till an 

 egg-pod of the locust is met with; into this the triungulin 

 at once eats its way, and commences to devour an egg. 

 Should two or more triungulins enter the same egg-pod, 

 battles occur till one is left. After a few days passed 

 in devouring a couple of eggs, the triungulin sheds its 

 skin and appears as a different larva [b], with soft skin, 

 short legs, small eyes, and different form and proportions; 

 a second moult takes place after about a week, but is not 

 accompanied by any very great change of form, though the 

 larva is now curved, less active, and in form like a larva 

 of Scarabaeidae ; when another moult occurs the fourth 

 instar appears as a still more helpless form of larva, which 

 increases rapidly in size, and when full grown leaves the 

 remains of the egg-pod it has been living on, and forms a 

 small cavity near by; here it lies on one side motionless, 

 but gradually contracting, till the skin separates and is 

 pushed down to the end of the body, disclosing a completely 

 helpless creature [c\ that has been variously called a semi- 

 pupa, pseudo-pupa, or coarctate larva; in this state the 

 winter is passed. In the spring the skin of the coarctate 

 larva bursts, and there crawls out of it a sixth instar [d] 

 which resembles the fourth, except in the somewhat 

 reduced size and greater whiteness. It is worthy of 

 remark that the skin it has deserted retains its original form 

 almost intact. In this sixth instar the larva is rather 

 active and burrows about, but does not take food, and in 

 the course of a few days again moults and discloses the true 

 pupa. As usual in Coleoptera this instar lasts but a short 

 time, and in five or six days the perfect beetle appears. 

 It is extremely difficult to frame any explanation of this 

 complex development; there are, it will be noticed, no less 

 than five stages interposed between the first larval instar 

 and the pupal instar, and the creature assumes in the 

 penultimate one a quasi-pupal state, to again quit it for a 

 return to a previous state. It is possible to look on the 

 triungulin and the pupal instars as special adaptations to 

 external conditions; but it is not possible to account for 



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