phidce, nearly all burrow in mud and sand. The imagos are 

 usually of medium size, barred with green or yellow, the 

 apical part of the abdomen often expanded to a greater or less 

 extent. They are usually seen near water, but are not numer- 

 ous as a rule. The ovipositor is rudimentary or wanting and 

 oviposition is exophytic, as in the remaining families. The 

 eyes are small and widely separated, in which respect the fam- 

 ily approaches the Zijcjopient. The nymphs of the u-Eschnidw 

 and Goinphidd' differ but slightly in the structure of the labium 

 and gizzard, and both these organs are quite similar to the 

 type found in the Zygoptera. The next family, Cordulegaster- 

 idw, is of special interest. It has but few species, and examples 

 are rarely seen in Illinois. While evidently related to the pre- 

 ceding families in different ways, the nymphs are like those of 

 the Lihellidkht in having a spoon-shaped labium and a sym- 

 metrically 4-toothed larval gizzard. The last family, Lihellu- 

 lid<e, comprises most of the commoner species. They are 

 diversified in structure and habits, and may be grouped in three 

 subfamilies. The first two of these ( Syntheniii/ue and Cordu- 

 li'ni(e) have a number of common features and have hitherto 

 been classed as one, but the wing structure and nymphal 

 characters of the Synthernihue, represented in Illinois by Ma- 

 cromia and Didymops, seem to warrant its separation from the 

 CorduU'nuv. The greater part of the family belongs to the Li- 

 belhiluHe, which includes three general types, exemplified by 

 SympetniiH (Diplax), Lihellala, and Tramea. The grouping of 

 these is based by Mr. Adams on the extent of development of 

 the ovipositor. 



LITERATURE. 



A list of the more important papers, to which references 

 are made, is appended to this paper. A brief summary of their 

 contents may be given here. 



On the nymphs, the most important papers are by Hagen 

 and Cabot, describing and figuring the nymphs of the Museum 

 of Comparative Zoology, at Cambridge. Cabot's first paper ( '7'2 ) 



