626 SCIENCE PROGRESS 



Moths, which are at once notable for the prominence of their 

 warts and the faciUty with which they assume the twig-hke 

 aspect, the resemblance is astounding. 



Concurrently, there appears a tendency for the colour of 

 these insects to vary from the green of the majority, many of 

 such caterpillars being of brown or yellow shades, all more or 

 less approximating to the general hue of twigs. These cater- 

 pillars are able to maintain the rigid attitude for hours and 

 nothing induces them to relax themselves. One instance, 

 that of the Scalloped Hazel Moth, is worthy of special mention, 

 for this caterpillar adds to the deception, or so it may be 

 assumed, by deliberately quivering in a very rapid and remark- 

 able manner. 



VI 



In a group of rather loosely allied species, among which 

 are some striking insects, such as the familiar " Puss," the 

 " Lobster," and the " Hook-tips," the development of warts 

 and humps has reached a specialised development which in 

 several cases modifies out of all recognition the normal cylin- 

 drical caterpillar form, and it seems more than likely that 

 this extreme variation is beneficial by giving the insect a re- 

 semblance to some other object which is either useless as food 

 to its natural enemies or positively harmful. Superficially 

 examined, nothing could be less caterpillar-like than the 

 Lobster larva, with its humped segments — appearing like a 

 row of teeth — its extremely long, jointed legs, and above all, 

 its extraordinarily enlarged anal segment, which being held 

 up at right angles to the rest of the body, suggests that this is 

 the head, instead of the tail, of the creature. 



An even more significant and striking character of this 

 caterpillar is the pair of fine filaments projecting from this 

 erected anal segment. It appears to be the simplest develop- 

 ment of a not merely protective, but quite ofi"ensive weapon, 

 for although it appears in this case to be comparatively inno- 

 cuous, it attains considerably more important development 

 in the related Puss. The anal segment of the Puss cater- 

 pillar is forked, each branch tapering to a truncated tip and 

 forming a sheath for bright red filaments, which can be 

 protruded to a considerable distance. When the insect is 

 alarmed, it waves the filaments in the air very vigorously. 

 The Puss has another specialised offensive weapon in the power 

 to eject strong acid from the first thoracic segment, on the 

 underside, the discharge often being thrown to a considerable 

 distance. 



In modified ways, all the devices hitherto reviewed re- 



