Special attention has to be paid to this snail, on account of its poisonous nature. 

 Even a small handful of them, thrown into a pail of water will cause cramps to fingerlings 

 within five minutes, and will kill them within eight minutes (Wundsch, 1930). 



Of clams, only Pisidlu, and upon occasion Spaerium will mostly be found in ponds. 



Dragon-fly larvae 



In everj' pond one will find all thres categories, the short, broad larvae of Libell- 

 ulldae, the slim, moderately broad Aeschnldae (up to 7 centimeter long at times), and the 

 very slim agriaiidae. 



A short time after planting, one car. follow their progress from week to week. The 

 young larvae, especially of agrionldae . are to be found in all ponds during the summer 

 months. Small forms of them compete for food with the fishes, larger ones will even prey 

 upon fish hatch. Vast throngs of the biggest ones are revealed only at drainage time, when 

 they are caught in the strainers. 



Ephemera larvae 



Together with chirononddae. they are most Important foodstuffs in a pond. This is 



especially true in regard to the swimming forms of them, the Cloeon species, mostly hidden 



in plants. Also the Caenia species are to be mentioned. Less apt in swinming, they remain 

 more at the detritus-rich bottom floor. 



St one fly larvae 



ttlll be found — especially Neumura varlegata — during the first period after spring 

 cultivation in all trout and carp ponds, supplied by creeks and strong currents* 



Meuropterae larvae 



The predatory larvae of Sialis (Alder fly) species are found in all mud deposits of 

 the pond. 



Trichopterae larvae 



Have also been found, quite often, in ponds; are only rare in newly cultivated ponds. 

 Only the small forms liJce Leptocerua and Trlsenodes attained mass developments in the caip 

 pond in Sachsenhausen, which was repeatedly found also in the practical industries. The 

 large larvae of Phryganea grandls are especially noticeable at drainage times, but their 

 number is usually not large. Also "naked" (lacking the shell) predatory larvae are to be 

 found, chiefly — naturally again — in trout ponds. 



Diptera larvae 



Ply and also mosquito and gnat larvae are of negligible importance. The limpid, plank- 

 tonic larvae of Sayonyla rests mostly near the bottoaa surface, while the larvae and pupae 

 of Llelusina are to be found, often in va»t numbers against the dike boards and other solid 

 objects of trout ponds. Chironomidae ^ of all forms, are the most irysortant and most 

 numerous of all the aquatics, upon which fishes will feed. In both, carp and trout ponds, 

 one will find representatives of the following species i Ceratopogon . Tanypus. Qrthocladlus. 

 Cryptochironomus . Chironomus and Tanytarsua . 



Chiefly to be classified among the vegetation fauna, and therefore possibly feeding 

 upon spawn are — according to Nordqulst (1923) — small forms of Orthocladius . of Tanytarsus 

 and divers larger, red forms, i.e. Ceratopogon fonns. All other forms are chiefly detritus 

 feeders, dwelling in the mud. 



Of multitudinous occurrence in carp ponds are mainly: Chircnonnis olumosus . C. th'^n^n^ . 

 Ehdochironcmma . Polypodilum. Nicrotendipes. Paratendipes . Orthocladius. Glyptotendipes . 

 Cryptochironomus . Tanytarsus . Ceratopogon ; in small flowong trout ponds: Tanytarsus 

 (Cregarious group), Tanypus (Sectio Tanypus ) . Microtendipes and Orthocladius . 



33 



