The Transformations of Insects. 



97 



the form of the future Umbs, wiiii^s, antenn;e, eyes, etc., is plainly indicated; in the 

 other these are hidden. The pupa of a butterfiv or a beetle is of the first type; that 

 of a house-fly of the second. But this difference is more apparent than real. The 

 butterfly chrysalis has thrown off the skin of the caterpillar ; but the maggot of 

 the fly has turned to a pupa without tasting its skin, which hardens into a 

 brown case of elliptical form ser\-ing as a protecti\'e cocoon and known as the 

 puparium. 



Now the scientific name larva ^ was given to the caterpillar because its form 

 was believed to be a mask for the butterfly that already existed in a wrapped- up 

 condition within. Swammerdam and other early investigators had detected the 

 rudiments of wings under the last skin of the caterpillar, and as the form of the 

 pupa had been seen through the transparent skin of a species of gnat-larva, it was 

 assumed that the forms of the pupa and the adult Insect already existed in the 

 larva whilst it was still in the egg. Each of these stages was considered to be a 

 distinct Insect, boxed up one within the other, and the shedding of the last cater- 

 pillar skin simply revealed the previously existing chrysalis, which in turn perished 

 to set free the winged butterfly. This was not a correct view, though later investiga- 

 tions have shown that there was a small basis of fact in the existence of \\-hat are 

 known as imaginal discs. What we know as metamorphoses are reallx' onlx- a 

 continuation of the changes 

 that have brought about 

 the evolution of the cater- 

 pillar from the embr\'o in 



the egg. To have enabled 



all these changes to take 



place in the egg would have 



necessitated the produc- 

 tion of only one or two 



enormous eggs instt'ad of 



hundreds, and tlic In-cct 



would lia\e had to grow 



allt r tile wingetl lorni had 



Wv\] reached. As it i>, tlitre 



is no growth after \\\v linal 



instar lias been reached. 

 The six true lt\gs of 



the caterpillar mav Ix' 



c o n s i d e re d permanenl 



structures. The\' de\'(>lop ( 



into the fei't of the ' 



long legs of the butt(i(l\-, 



and any injurN' to lluin in 



the caterpillar ^tag(■ pro- 

 duces some abnormalitv in 



the legs of the butterfly. 



Photo by] 



.\ 1,1,1 Chirk. 



I'AK.S OF 



A small portion of the cluster of cgRs laid by ;lie ligli: brociuic moih oi. broom and otluT 

 plants. They are magnified thirty times, and serve to illustrate the beautiful manner in 

 which the eggs of Insects are frequently sculi)tured. 



' Latin, a mask. 



