75 



only such forms of insects that were aerial or at least in that 

 stage at the time they were used in the experiments. In these 

 tests only half-grown or larger nymphs were taken. No other 

 food than land insects was given them and these in most cases 

 were dropped in the feeding jars alive. Some of the nymphs 

 were carried through in this way for one or two moults, or until 

 they finally emerged. In some cases this feeding period was 

 carried on for from two to five weeks. All the different spe- 

 cies of insects fed were readily eaten, except most of the ants, 

 especially those strong in formic acid, and some aphids. 



Beside adult insects, caterpillars, maggots and gi-ubs of vari- 

 ous kinds, also other small creatures, such as spiders, land Crus- 

 taceans (shrimps and sowbugs), millipedes, earthworms, and 

 nematodes were fed to the nymphs. All these were eagerly 

 snatched at and eaten up. 



Often when no other food was available, small bits of fresh 

 beef seemed to be relished. 



That dragonfly nymphs do feed on land insects under nat- 

 ural conditions is borne out by the findings in the contents of 

 the alimentary canal of the 253 nymphs dissected, as listed 

 above. Out of this number, 20 nymphs were found to contain 

 aerial forms, thus representing 7.9 per cent, of the number dis- 

 sected ; or, if this number is expressed in units, to conform with 

 the tabulated statement, then the land insects consumed by these 

 nymplis constitute 7.9 per cent, of their food. 



Field Observation and Examination of the Contents of 

 THE Alimentary Canal of Adults. 



In this series of dissections 218 Pantala and 2-1 Anax (ex- 

 cluding those whose alimentary canal was found empty) were 

 taken. To these figures may be added a number of tlragonflies 

 that were caught with the victim still more or less intact in 

 their mouth parts. As the mouth parts are really part of the 

 digestive tract, the insects thus found will be included in the list 

 of those found in the alimentary canal proper. 



As there seems to be a slight difference in the food habits 

 between the Pantala and Anax, as indicated by the observations 

 so far made, the findings of the two species will therefore be 

 given under separate tables, as follows : 



