1 88 THE BIOLOGY OF INSECTS 



Apparently these abnormal insects at all stages experience 

 a difficulty in shedding the cuticle : " Sometimes ... an 

 individual resembles neither a pupa nor a larva, as it has 

 the head and thorax of the former and the abdomen of the 

 latter." A fact of much interest discovered by Singh-Pruthi 

 is that in the abnormal mealworms only a part of the wing- 

 rudiment is external ; the remainder Hes as usual within 



Fig. 53. — A, Mealworm (Larva of Tenebrio molitor) , with abnormal 

 external wing-rudiments iw) , partly dissected to expose food-canal 

 (5, stomach; i, intestine; r, rectum); a, fat-body; t, testis. X 3. 

 B, Transverse section through thorax. X 20. e, epidermis ; c, c' , old 

 and new cuticle ; 5, stomach ; m, muscles ; b, wing-rudiment, part 

 external and part in pouch {p) . After H. Singh-Pruthi (Proc. Camb. 

 Phil. Soc. Biol, i, 1924) . 



the inpushed pouch of the skin (Fig. 53, B,^). This indicates 

 that a portion only of the wing-bud was everted during the 

 preparation for the preceding moult. During the last 

 twenty years somewhat similar observations have been made 

 on the larvae of other beetles and of certain moths ; of these 

 the most noteworthy is the case of the ground-beetle Lehia 



