88 INSECT TRANSFORMATION 



the new cuticle grows over these, and thus is formed a quiescent 

 nymph or " pupa " (Fig. 47/), lying hidden and protected by 

 the hardened larval-cuticle or " pupa-case ". From this in due 

 time the imago emerges, the case opening with a dorsal T- 

 shaped slit through which the fly comes forth having already 

 worked off the delicate nymph-cuticle (Fig. 47 g). The thorax 

 first appears, followed by the head ; then are withdrawn the 

 feelers and legs, and finally the abdomen. 



From this brief account of the development of the snowy- 

 flies, it will be seen that they pass through a marked trans- 

 formation in the course of their life-history. The way in which 

 the appearance of the wing-rudiments is postponed until the 

 last stage but one agrees with what happens in the life-history 

 of the butterfly ; and were these wing-rudiments growing 

 inwards during the larval stages, the snowy-flies would have 

 to be included among those insects that practise the hidden 

 type of wing-growth. Their structure, both larval and adult, 

 shows that they are nearly related to families of insects the 

 Suckers (or PsyUidae) for example in which the open type of 

 wing-growth is evidently the rule ; thus they afford an interest- 

 ing and suggestive intermediate condition, the importance 

 and significance of which will be discussed in the last chapter 

 of this volume. 



Another family of sucking insects allied to the snowy-flies 

 afford us also examples of a type of life-history very similar, 

 but complicated by a striking divergence between members 

 of the two sexes when adult. These are the Coccidae, 1 in- 

 cluding the Scale-insects and " Mealy-bugs ". The tiny 

 males (Fig. 48 a) in this family have long, jointed feelers and 

 comparatively ample forewings, so that they are active fliers, 

 but the hindwings are modified into short, twisted, thread- 

 like organs, and the beak and piercers are so much reduced that 

 the insect takes no food after attaining the winged condition. 

 The newly-hatched larva (Fig. 48 c), oval in form, resembles 

 somewhat that of a snowy-fly, but has the segmentation of 

 the body better marked and the feelers and legs more typically 

 developed ; the beak is short and conical ; the piercers, very 



1 R. Newstead : " Monograph of the Coccidae of the British Isles ". 

 London, 1901-3. A. D. MacGillivray : " The Coccidae ". Urbana, Illinois, 

 1921. 



