larvae were collected opportunistically from tammany creek , nez perce co. , i d ( 46 21.51.51 n , 117 03.32.05 w ) , a perennial , undammed creek approximately 13  m in width and roughly 10  km in length .
tammany creek drains into the snake river approximately 770  km from the confluence of the snake and columbia rivers .
we surveyed the study area ( 1  km in length ) on foot and collected odonates by drag net from 15 february 2012 to 12 march 2012 . upon collection ,
larvae were transported to lewis - clark state college and housed in 50-ml plastic vials with a 3-mm - diameter dowel for perching .
larvae were measured with a millimeter rule for total body length and head width and maintained on a photoperiod of 14:10 ( l : d ) h cycle at an ambient air temperature of 22c .
vivida head 24.5  mm , body 619  mm ; a. palmata head 48  mm , body 2335  mm .
behavior trials were conducted in 250-ml containers with filtered tap water and a singular 3-mm - diameter perch .
one shrimp was placed in the container , as alternative prey , 1  min after simultaneously placing both odonates in the container .
vivida head 34  mm , body 1117  mm ; a. palmata head 48  mm , body 2335  mm . to evaluate whether the observed behaviors were species specific , we tested a. palmata and ar .
animals used in congeneric trials ( not diagrammed ) were matched for total body length as closely as possible ( 31 ar .
vivida , a previously undescribed luring behavior was observed by either a. palmata or ar .
that luring behavior was demonstrated , the a. palmata attempted , unsuccessfully , to capture the shrimp prior to the luring behavior . luring behavior
was initiated only when the odonates had entered into the field of view of one another . once the a. palmata and ar .
vivida had oriented toward each other , a brief period ( 3060  s ) of no visible movement ensued . in four of five trials
d ) sequence of points in luring abdominal movement by a. palmata during a. palmata ( large ) versus ar .
. 
 abdominal movement to the side and exposure of the abdomen of a. palmata to ar .
vivida changed position to place the abdomen of a. palmata directly in the field of view ( fig .
this behavior consisted of 710 movements of the abdomen within approximately 2  s ( fig .
( a  d ) sequence of points in luring abdominal movement by a. palmata during a. palmata ( large ) versus ar .
. abdominal movement to the side and exposure of the abdomen of a. palmata to ar .
ar . vivida changed position to place the abdomen of a. palmata directly in the field of view ( fig .
this behavior consisted of 710 movements of the abdomen within approximately 2  s ( fig .
vivida luring a. palmata was observed . the following sequence of events details that observation ( fig .
2a).the abdomen was then fully moved to the opposite side of the body in a slow motion ( 2  s ) and held on the other side of the body for approximately 8 s ( fig .
2b).step 2 was repeated to the initial side of luring . at this point , ar .
vivida positioned its abdomen directly behind its head and slowly continued movement toward head of a. palmata .
vivida attempted to capture a. palmata at its head.upon being struck , a. palmata slowly retreated.ar .
vivida continued attempts at luring a. palmata , with rapid abdominal movements to the initial side for approximately 5  s. while luring , ar .
vivida slowly approached the retreating a. palmata.the sequence was broken as a. palmata used abdominal thrusts to propel itself away and over ar .
the abdomen was then fully moved to the opposite side of the body in a slow motion ( 2  s ) and held on the other side of the body for approximately 8 s ( fig .
step 2 was repeated to the initial side of luring . at this point , ar .
vivida positioned its abdomen directly behind its head and slowly continued movement toward head of a. palmata .
vivida continued attempts at luring a. palmata , with rapid abdominal movements to the initial side for approximately 5  s. while luring , ar .
the sequence was broken as a. palmata used abdominal thrusts to propel itself away and over ar . vivida . in the other 13 of 18 a. palmata versus ar .
, a. palmata actively pursued the shrimp prey item , catching and consuming the prey without attacking the ar .
vivida positioned itself at the bottom of the chamber and remained motionless for the entirety of the trial .
vivida pursuing the prey . in all of these trials , the a. palmata captured and consumed
vivida attempting to consume the prey item after the a. palmata had caught and began consumption . in this instance , the ar .
vivida was consumed by the a. palmata following consumption of the prey . in one trial , ar .
vivida actively attacked and consumed the prey , and a. palmata remained motionless in the chamber . in every congeneric trial
vivida , 12 a. palmata versus a. palmata ) , there were no instances of attack , luring , or attempted consumption of the congeneric by either animal .
in our trials , luring occurred only when a head - to - head orientation was present .
this is the same orientation described in the well - known agonistic behavior of many larval odonates ( corbet 1999 ) .
however , in contrast to previously described agonistic behaviors , predatory luring occurred between different odonate families with a different repertoire of movements ( figs . 1 and 2 ) and typically ended in consumption of the prey . in trials where luring was not displayed
a caudal attack by either species typically resulted in one of two possible scenarios : 1 ) removal of lamellae of ar .
vivida and subsequent retreat and avoidance of further attack by prey and 2 ) prey being grasped and subsequent retaliatory bites and aggression resulting in injury to the predator ( e.m . , personal observations ) .
these two scenarios , we believe , are the reasons for the head - to - head orientation that has been demonstrated as critical for the luring to occur .
the caudal luring by the predator caused the lured individual to change orientation slightly to ensure that a successful attack was achieved .
the exaggerated slow swaying of the caudal region caused the lured individual to change orientation .
the subsequent rapid movements of the caudal region resembled that of the preferred prey in this environment , the freshwater shrimp , which further provoked the lured individual to investigate .
the movement of the lured individual from the head - to - head orientation to the more vulnerable position of focusing on the lure provided the predator an opportunity to strike at the prey .
we believe that more instances of predatory luring would have been observed had the time duration of the trials been longer than 7  min .
all animals used in the trials were nave , not having been involved in any trials previously .
we can not comment on the experience of the animals in the field before capture ; however , all animals were housed individually for 3 weeks before trials were conducted . the luring demonstrated by ar .
vivida , even though consumption was not achieved ( although a strike at the head of the much larger a. palmata did occur ) , may indicate that this behavior can be used in situations other than predation .
vivida is similar to the agonistic behavior of other coenagrionidaen odonates ( rowe 1992 ) , several differences exist .
3 ) the behavior displayed by ar . vivida to physically lure the larger a. palmata close to the ar .
vivida versus a. palmata with closely matched sizes will help elucidate whether this behavior is predatory or used to ward off potential predators .
although there was no luring of a. palmata by other a. palmata , similarity of ar .
the possibility of predation by a congeneric may induce the larger dragonfly to lure the smaller but morphologically similar damselfly to a position in which a fatal attack is much easier and much more likely .
vivida and a. palmata at this locale creates the possibility that large larvae are likely to encounter smaller conspecifics .
 organisms in the order odonata are highly predatory insects that have a wide distribution globally . to date , there has been zero evidence that odonates employ luring as a means of prey acquisition . 
 however , in this study , we show that aeshna palmata larvae use abdominal movements to lure larval argia vivida , subsequently consuming the lured organism . 
 we also present findings of a similar behavior from larval ar . 
 vivida in an attempt to lure larval a. palmata within striking distance . 
Materials and Methods
Results
Discussion