Observations on the Life History of Taphrocerus gracilis 9 



out completely. At the time of its emergence, a round hole is made in 

 the top of the beetle egg thru which the adult parasites emerge. 



A larval parasite, only three specimens of which were seen, was found 

 in the mines of the beetle larvae. This was an external parasite, deter- 

 mined by Dr. A. A. Girault as a new species {Achysocharis donna). Other 

 larval parasites that were found have not yet been determined. 



Behavior of the beetles 



Temperature seems to be a factor strongly influencing the behavior 

 of Taphrocerus gracilis. Observations have shown that on a warm, 

 sunny day the beetles are actively feeding on the leaves of the bulrush, 

 and that they fly quickly when disturbed. On a cold day, and especially 

 early in the morning, the beetles are inactive and are found in the crevices 

 between the bases of the leaves and the stalk of the bulrush, and they 

 retract their legs and fall back into the crevices when disturbed. 



In the field experiments, the beetles were approached when on the 

 bulrushes, and if they did not respond in some way a pair of forceps was 

 waved near them. They would then either retract their appendages and 

 fall, fly away, or cling to the leaves. If they clung to the leaves, they 

 were mechanically stimulated by touching with the forceps until they 

 were forced to contract and fall, or to fly away. Sometimes all three 

 reactions would be obtained from a single individual. At first it would 

 cling to the leaf; when further stimulated it would retract its appendages 

 and start to fall, and then it would begin to fly. Such a complex response 

 was common at temperatures between 19° and 20° C. It was as if the 

 beetles were slightly torpid and the beginning of flight was delayed by 

 the slowness of response. If the beetles were in such a position on the 

 leaves that they fell into the crevices at the base, flight never began at 

 all. If they were out near the tips of the leaves and actually fell, flight 

 might begin before they reached the water, at the above-named tempera- 

 tures. At lower temperatures the beetles were rarely found out near the 

 tips of the leaves, but when they were they would fall great distances 

 without flying at all. 



A summary of 190 experiments in which different beetles were used for 

 each experiment, except possibly when the same beetle was accidentalh' 

 met with on different plants, is given in table 1: 



TABLE 1. Reactions of Three Lots op Beetles to Mechanical Stimulation at 



Different Temperatures 



(Numbers of beetles iii respective lots, 27, 33, and 130) 





Temperature (degrees centigrade) 



Reaction 



Be'ow 19° 



From 

 19° to 20° 



From 

 20° to 30° 



Per cent that contracted 



89 



4 



18 



39 



54 



. 54 



40 



Per cent that flew . , 



77 



Per cent that clung to leaves 



22 









