270 INSECT TRANSFORMATION 



(Curculionidae). In Jurassic rocks the remains of Coleoptera 

 are fairly abundant, the English Purbeck having yielded 

 bark-beetles (Scolytidae), while from Tertiary deposits such 

 as those of Florissant, Colorado and the Prussian Amber 

 (Oligocene) and the Miocene marls of Oeningen, a large number 

 of fossils referable to living genera have been described, 

 including some 400 species of weevils. The mandibulate jaws 

 of adult beetles and the primitive, campodeiform type of 

 larva that characterizes many of their families (pp. 99-106) 

 suggest relationship to the Megaloptera, and their ancestral 

 stock must be sought in Palaeozoic times probably at the 

 latest from the older Permian before the mecopteroid and 

 megalopteroid branches had diverged from the primaeval 

 Endopterygota. 



The Hymenoptera with their combination of biting man- 

 dibles, suctorial labium, wings with reduced and specialized 

 nervuration, foremost abdominal segment annexed by the 

 thorax and numerous kidney-tubes, stand apart from all 

 other endopterygote insects, and the earliest known fossils, 

 very few in number from the Jurassic beds of Germany and 

 Spain are referable to both the existing sub-orders, Apocrita 

 and Symphyta. In deposits of Tertiary age Hymenoptera 

 became more numerous, and the most specialized of recent 

 families such as bees and ants were living in Oligocene 

 and Miocene times. The caterpillar larvae of the saw-flies 

 are analogous to those of the moths and butterflies ; while the 

 likenesses between them may be due rather to parallel evolution 

 than to near relationship, it is suggestive that the arrange- 

 ment of bristle-bearing tubercles on the segments of primitive 

 moth-caterpillars can be derived by reduction from that 

 which characterizes saw-fly caterpillars. 1 The Hymenoptera 

 must have arisen far down the endopterygote stem ; possibly 

 having a common origin with beetles, but more probably as 

 an early offshoot from the primaeval Mecoptera, rapidly 

 becoming highly specialized, not only in the structure of the 

 imago of the higher families combined with the degeneration 

 of their larvae into small-headed, legless grubs, but also in 

 the elaboration of their modes of behaviour leading on to 



1 H. G. Dyar : "A Classification of Lepidopterous Larvae". Ann. 

 New York Acad. Sci., VIII. 1893. 



