No. 39] ODONATA OF CONNECTICUT 17 



in form than occur in many orders, and the term naiad would be 

 Hmited to the young of Plecoptera, Ephemerida and Odonata. 

 Since the term has not been generally adopted, however, the word 

 nymph is used here to designate the young of Odonata. 



Odonata, Plecoptera (stoneflies) and Neuroptera (ant lions and 

 dobson flies) are more closely related to one another than to other 

 orders of insects ; but although similar in many points, are readily 

 distinguished in nymphal and adult stages. The basis of separa- 

 tion of adult Odonata from the Neuroptera and also the Ephe- 

 merida lies in the presence of the nodus in the wing of all represen- 

 tatives of the dragonfly group. The nymphs are easily distin- 

 guished from others of similar form and habits by the possession 

 of a hinged labium which folds beneath the head and is capable of 

 being extended beyond the tip of the latter. The Neuroptera have 

 no vestigial wings in the earlier stages, differing in this point 

 from the Odonata. 



Geologically, the dragonflies are one of the oldest orders, dating 

 back to the Carboniferous period when related forms occurred 

 with a wing-spread of more than two feet. Gradations between 

 the Neuroptera and Odonata appear in these early periods and 

 show with more or less certainty that the ancestors of the order 

 were closely related to the Neuroptera of today. 



Among Odonata, the more generalized or simpler condition as 

 regards structure seems to be found in the Zygoptera. This theory 

 has been questioned by Needham, who holds that Anisoptera are 

 really simpler because of their wing venation. Taken as a whole, 

 however, it seems probable that the Zygoptera have retained a 

 simpler structure in most features. Moreover, the recent dis- 

 covery of true Zygoptera in the Kansas Permian leaves no choice 

 but to accept the former interpretation. 



Scientists have recognized 2,400 or more species of dragonflies 

 throughout the world (Tillyard 1917, p. 300). Muttkowski in 

 1910 listed 494 species from North America, and of these, some 

 160 occur in New England. Many of them have a wide range 

 and may be expected to be found almost anywhere in the United 

 States. 



Compared with Coleoptera or beetles, for instance, dragonflies 

 are few in numbers. A recent publication has described 1,084 

 species of weevils from the northeastern United States, and one 

 author states that nearly 4,000 species of beetles probably exist 

 in the State of Indiana. Our Check List of Connecticut Insects 

 records 1,452 species of Lepidoptera (moths and butterflies) 

 within the State and only 10 1 Odonata or dragonflies — showing 

 the relative scarcity of dragonflies as compared with other insects. 

 The number of species of dragonflies captured in Connecticut to 

 date totals 112 and leaves about 50 of these herein described yet 

 to be found. 



