Animah of the Mississippi Bottoms near Qaincy. 175 



have an effect as fish food, and otherwise on aquatic life. At 

 Qaincy, a small cricket {Tridadi/las apicaUs) occurred in 

 myriads atoong weeds which were springing up from the mud 

 at the edges of sloughs, and individuals were sometimes found 

 upon the water. 



ORDER PLECOPTERA. 



Small insects, which, as nymphs, live under rocks and 

 boards, often in swift-flowing water. The pupa takes food, 

 and after attaining its growth leaves the water, and transforms 

 to the winged adult. In a number of points they are allied to 

 the grasshoppers. 



Flecoptera^ nymph. 



A flat nymph found in Willow Slough. It is about .52 

 inch long and bears at the end of the abdomen two long, jointed 

 appendages. The antennae are long and slender, the mouth 

 parts much like those of a grasshopper or cockroach. Head 

 very wide, and with a pair of compound and three simple eyes. 

 Three divisions of the thorax large, with expanded terga, and 

 bearing at each side cottony respiratory tufts. Legs with strong 

 femora and three-jointed tarsi. 



They were not common at Quincy, probably because the 

 waters do not furnish them suitable shelter. 



ORDER ODONATA. (Dkagon Flies, Snake Feeders.) 



These are predaceous when adult, feeding upon gnats, 

 mosquitoes, flies, etc., which they capture while flitting rapidly 

 about. Dragon fly larvjE and pupae have the reputation of 

 preying upon other insects, and as a rule this will probably be 

 found true; but an examination of several larvas shows them to 

 be in some cases largeh^ vegetable feeders and possibly scaven- 

 gers, the alimentary canal containing numbers of de.^mids, dia- 

 toms, fragments of moulds, and a good deal of material (prob- 

 ably slime) gathered from the bottom for the small organisms 

 and the organic matter contained in it. The eggs are dropped 

 into the water as the females fly over it, or may be attached to 

 submerged plants. Members of one genus are said to go be- 



