| Baiting is the main method for the control of red imported fire ants,Solenopsis invicta Buren.The efficient food transport behavior is the key factor of the success of bait.Our previous observation showed red imported fire ants usually perform food burying during the foraging processes.However,the details of this behavior is largely unknown.In addition,fire ants always foraging on the tree trunks because of the honeydew-producing Hemiptera and some small arthropods.Nevertheless,it is still unclear how fire ants transport food on tree trunks.This study took high resolution videos in the laboratory to observe the food burying behavior of fire ants,and then observed under the field condition.Meanwhile,high resolution videos were taken on the tree trunks to observe the vertical food transport behavior,and the effects of food shape and placement on vertical food transport were also studied.The main content and results:(1)Food burying behavior of red imported fire ants:when starved in the laboratory,food(sausage)was consumed by large numbers of ants,and few burying behaviors were observed.However,when food was provided until satiation of the colonies,food-transport was suppressed and significantly more soil particles were transported when compared with these colonies exposed to starved conditions.This result showed food burying behavior related to the lower feeding intention of ants.In the food burying processes,soil particles were preferentially placed adjacent to(in contact with)the food items at the beginning,and after the edges were covered,ants transported significantly smaller soil particles to cover the food.Meanwhile,larger particles were pulled/dragged around(but not in contact with)the food.Interestingly,only a small number of ants,mainly the small workers,were involved in food burying,and the ants tended to repeatedly transport soil particles.A total of 12 patterns of particle transport were identified,and soil particles were most frequently picked from the foraging arena and subsequently placed adjacent to the food.In the field,almost all released food was actively transported by S.invicta workers and no burying behavior was observed.This study is the first to show the details of food burying behavior in red imported fire ants,and our results could help control fire ants precisely.(2)Vertical food transport behavior of red imported fire ants:S.invicta used multiple strategies to transport food items on vertical surfaces(tree trunks).Small food items(1×1×1mm sausage)were carried and transported by individual ants,and larger food items were either collectively and directly transported or cut collaboratively first and then transported by groups of ants.Competition and deadlocks were frequently observed during food transport behavior on the vertical surface.During cutting,groups of ants tightly fixed the food on the tree trunks by holding the edges of the food item,while other ants cut the food into smaller particles and then transport individually or collectively.Food items were placed on the platform or fixed on the tree trunks had no significant effect on vertical transport,but food shapes had significant effects on vertical transport.In collective transport of medium-sized food(9 mm~3),ants spent significantly shorter time to transport the cuboid food(2.1×2.1×2.1 mm)compared with flattened ones(3×3×1 mm).However,in cutting transport of large-sized food(64 mm~3),ants spent significantly less time in moving cuboid food(4×4×1 mm)than flattened ones(8×8×1 mm)during the lifting-to-vertical phase but more time during the transportation phase.This study is the first to show the details of vertical food transport behavior of red imported fire ants,and our results could improve the baiting system on tree trunks. |
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