1920 ENTOMOLOGICAL SOCIETY. 105 



REMAEKS OX T-HE ANCESTRY OF INSECTS AND THEIR ALLIES. 

 G. C. Cbampton, Massachusetts Agi!icultural College. 



It has beeii a matter of considerable surprise that so much time and attention 

 have been expended upon the subject of the evolution of mammals, reptiles, and 

 other vertebrates, to the practical exclusion of the consideration of the development 

 of the lines of descent of the insects, Crustacea, "Myriopoda," and other arthropods, 

 especially since the study of the latter forms involves no great outlay in the matter 

 of collecting expeditions, equipment, housing facilities, etc., as is the case with 

 the study of the vertebrate groups. In fact, the arthropods offer unrivaled oppor- 

 tunities for the study of evolution, including, as they do, the greatest number 

 of species of living things, as well as a marvellous range of modifications in adapta- 

 tion to varied environmental conditions, and a height of development of the psychic 

 faculties (social instincts, etc.) unapproached elsewhere save in the group Mam- 

 malia. In addition to these advantages, the ease with which many of them can be 

 obtained, and the fact that no elaborate equipment or technique is necessary for 

 studying their external anatomy brings the group within the reach of practically 

 everyone, and it is most earnestly to be hoped that so fertile a field for researcli 

 will soon attract a number of investigators commensurate with its great possibili- 

 ties and its importance from the standpoint of evolution. 



Not only has this potentially rich field of research been sadly neglected, but 

 even the meagre investigations which I was able to csltyj out during the past 

 summer very quickly demonstrated that the prevalent conceptions concerning the 

 meaning of the parts in insects (as interpreted from the standpoint of a com- 

 parison with the structures of Crustacea and other arthropods) are in many cases 

 wholly erroneous. Thus the oft repeated statement that the " superlinguae " or 

 '■ paraglossae "' on either side of the hypopharynx of insects represent the first 

 maxillae or '" maxillulae " of in.sects is quite wrong, since the structures in 

 question clearly correspond to the so-called paragnaths or structures on either 

 side of the median ridge (corresponding to the hypopharynx or tongue of insects) 

 in the mouth region of certain Crustacea — and the '' superlinguae " or '' para- 

 glossae " therefore cannot be regarded as the appendages of a distinct " super- 

 lingual " segment in insects, as Folsom has claimed is the case in these forms. 

 The investigations of all embryologists other than Folsom have clearly shown that 

 the ' '" superlinguae " are not appendages of a distinct segment ; but practically 

 all recent entomologists have been led astray in a matter which could easily have 

 been righted had they but taken the trouble to examine the corresponding parts 

 in the lower insects and Crustacea. Furthermore, a study of the Crustacea clearly 

 demonstrates that the first maxillae of insects correspond to the first maxillae 

 of Cnistacea, while the second maxillae of insects (i.e. the halves of the labium) 

 correspond to the second maxillae of Crustacea, and the head of an insect is there- 

 fore comprised of but six (not seven) segments, as embryology has long indicated 

 to he the case. 



The statement that the parts of an insect's mandible are comparal^le to the 

 parts of the maxillae, which has received universal acceptance in the textbooks 

 dealing with the subject, is at once seen to be impossible when one compares a 

 series of crustacean mandibles with those of insects, since such a comparison very 

 clearly shows that the insect's mandible represents the basal segment alone of the 

 corresponding appendage in the Crustacea, while the maxillary galea and lacinia 



8 E.S. 



