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Show Knowlton: 1937J Control of the Beet Leafhopper in Utah appeared to be the intended place of insertion. 119 As the body of the leafhopper took on a bluish, semi-empty appearance the predator fed during the next two minutes for shorter and .shorter intervals of time at each of a number of points including the eye. In one case considerable force was exerted, and the tip of the rostrum appeared to enter for a short distance between two sc1erites ' of the leafhopper's abdomen, necessitating the use of the pro-thoracic tarsi to disengage the beak and rearrange the stylets, some of which appeared to have escaped from the labium. The total elapsed feeding time was 26 minutes. One minute later a third leafhopper was captured, but it escaped from the predator's grasp and was then kicked away by a hind leg of the [erus. Six minutes later, and on the sixth trial, the ferus secured another tenellus, and soon commenced feeding on the head at the base of the left antenna. Again the up and down movement of the damsel bug's head and pro-thorax was noted during most of the three minutes of feeding at this point. Slight movement of the leafhopper was still evident after four minutes of feeding, when the predator walked around carrying the leafhopper at the end of its beak. Feed ing continued for a total elapsed time of 17 minutes. After the leafhopper was discarded, the predator preened its mouthparts with its pro-thoracic tarsi, then darted at another leafhopper, which escaped. In some cases Nabis [erus individuals would take a number of tenellus victims in succession; in other cases one seemed to be sufficient. It was noted that some of the feeding ferus bent their heads down at an angle, exposing a dorsal shining area between the head and pro-thorax. A struggle usually ensued when two [erus attempted to feed upon the same leafhopper simultaneously, the original possessor usually retaining its prey. Nabis alternata Parsh.-A mature female Nabis alternata (Fig. 6) was caged in a four-dram homeopathic vial with eight beet and ob leafhoppers, served under a binocular microscope. In less than one minute the damsel bug seized a nearby male E. tenellus and inserted its stylets through the dorsal suture between the thorax and abdomen; the predator used its pro-thoracic tibiae and tarsi to capture and hold its After one minute of feeding, prey. the predator ceased using its legs to hold its victim, but continued to feed in the original puncture for five minutes. The pro-thoracic tarsi were then used to manipulate the leafhopper, with feeding being resumed for ope-half minute at the base of the right pro-thoracic trochanter. Feeding continued for two and one-half minutes at this point, then the leafhopper was turned to other positions, with feeding in each of the three places occurring for less than one minute each. Feeding then progressed for seven minutes through a puncture made near an abdominal spiracle on the left side, and later at a nearby suture. Feeding occurred over a total elapsed time of 34 minutes, then the dead ienellus was discarded. A second leafhopper victim was seized within twenty seconds, and feeding occurred through a dorsal puncture behind the second abdominal segment. The stylets were withdrawn and re-inserted in a number of places before feeding was discontinued after twenty-four minutes. The abdomen of the leafhopper was plump when feeding began, but much shriveled when the N. alternata discarded its dead prey. Nearly all feeding occurred through punctures made at sutures. Feeding continued for shorter periods at a time in later punctures than when feeding had just begun, possibly because body fluids in the leafhopper had become less plentiful in the partially desiccated insect being fed upon. During the three hours that the N. alternata was re tained in the vial, it fed upon and killed three E. tenellus, kicked several away which approached while feeding was in progress, and captured a fourth speci men which later was released without feeding having occurred. In most re spects N. alternata specimens under observation behaved like N. abis [erus. |
