TRANSFORMATIONS OF THE INSECT. 69 



ovate, flattened, with four long set<« in front and two behind, 

 with the sides of the body eniarginate and spinuhited. They 

 were found under logs. "When the larva is full grown, it de- 

 taches itself from the skin, which retains its form, and within 

 which the insect changes into a white opaque fleshy grub con- 

 sisting apparently of thirteen segments which gradually dimin- 

 ish in size from one end to the other. There are no liinb-cases. 

 According to analogy the pupa should be ' incomplete ; ' it is 

 probable, therefore, that the legs and wings make their appear- 

 ance at a later stage. If this be so the perfect form is oilly 

 attained after passing through three well-marked stages. I re- 

 gret, however, that the specimens at my disposal did not enable 

 me to decide this point." (Trans. Ent. 8oc. London, Third 

 Ser. i, 18G2.) 



Ilaliday states that Tlirips goes through ix, j^ropupa and pupa 

 stage. There are Ave well-deflned stages in the Ilomopterous 

 Tuphlocyha^ and more than three in Aphis. Yersin has noticed 

 several stages in the development of Gryllus campestris, and 

 the genus Fsocus has four such stages. 



The duration of the different stages varies with the changes 

 of the seasons. Cold and damp weather retards the process of 

 transformation. Re'aumur kept the pupa of a Butterfly two 

 years in an ice-house before, on being removed to a warm place, 

 it changed to a butterfly. Chrysalids survive great alter- 

 nations of heat and cold ; they may be frozen stiff" on ice, and 

 then, on being gradually exposed to the heat, thaw out and 

 finish their transformations. 



Retrograde Development. There are certain degradational 

 forms among the lowest members of each group of Insects 

 which imitate the group beneath them. The Tardigrades (which 

 are considered by some authors to be allied to the Mites) are 

 mimicked by the low parasitic worm-like Demodex folUcuJormn ; 

 the low Neuroptera, such as Lepnsma. imitate the Myriopoda ; 

 and the wingless Lice remind us of the larvae of the Neuropter- 

 lous Hemerohius. 



Among the Coleoptera, the history of Stylops affords a strik- 

 ing exanii)le. The active six-footed larva is transformed into 

 the strange bag-like female which takes on the form of a cylin- 

 drical sac, the head and thorax being consolidated into a 



