The Weta 42: 27-30 27 Interaction between a New Zealand native bee (Leioproctus sp.) and the pitcher plant Sarracenia flava.

Julian D Brook P.O.Box 9377, Newmarket, Auckland 1149. Email. [email protected]

Abstract As a cultivator of insectivorous Sarracenia pitcher plants I recently observed New Zealand native bees of the genus Leioproctus consuming the secretion on lids of plants in my collection. I am not aware of this interaction between New Zealand Leioproctus sp. and Sarracenia having been recorded before.

Introduction Pitcher plants of the genus Sarracenia are native to North America, their leaves having evolved into a passive pitfall trap. These pitchers are surmounted by an overhanging lid, or hood, in most cases, attracting predominantly flying via colour, form and sugar rich secretions. My collection of 125 individual plants are grown outdoors year round, being fully exposed to the elements. They are grouped together in two large display boxes which are sited within a paved patio surrounded by planted garden beds of mixed native and exotic flowering plants. Typical insects attracted to and captured by Sarracenia at the location include: Calliphoridae, Muscidae, Sarcophagidae, Eristalis tenax, Culicidae, Vespidae, and Bombus spp.

The bee genus Leioproctus has 17 native New Zealand species (Donovan & Maynard 2010). They are essentially solitary bees typically digging a nesting tunnel in suitable soil (Donovan et al., 2010) and can appear as a community given that a number of individuals will utilise the same suitable nesting habitat. As such, they have been itinerant nesters in the soil of the

28 Julian Brook garden beds that surround the Sarracenia at the site for several summer seasons.

This paper records my observations of the bees feeding from Sarracenia flava over a period of several days in December 2010 in my garden in central Auckland.

Observations During a period of settled sunny weather during early December 2010, I observed the bees visiting the pitcher lids repeatedly between 10am and 11am over a five day period. On the fifth day only one bee was observed and while their nest holes remained in the neighbouring soil for some time following this last observation they were not observed at all from that time. The corbiculae in 50% of individuals were laden with pollen (Fig.1). However, the pollen carried by these individuals was not collected from Sarracenia as all flowers had ceased to produce pollen or had been removed prior to the bees’ visitation. There was only ever one individual at a time on any given pitcher lid and no more than four visiting the plants at any one time.

Leioproctus interacted with S.flava exclusively rather than any of the other seven Sarracenia species present in the collection during the time I observed them. Under the climatic conditions at the location, the observation period coincided with the peak growing season of S.flava wherein the production of attracting secretions is at its highest.

The Weta 42: 27-30 29

Fig..1. Leioproctus sp. feeding on Sarracenia flava secretion. ©JD Brook 2011

Having landed, the bees traversed the lid of the pitcher, eventually slowly circumnavigating the lid margin where the sugar rich secretions produced by the plant are heaviest. Each visiting bee fed from the globose secretion by extending its proboscis into it. The bees fed in this manner for periods ranging between 3 and 10mins. Having stopped feeding, the bees then moved very little or remained stationary (ranging from 5-12 minutes) until such time as they flew away. During this time most individuals remained with their wings folded back. However, a small number remained motionless with their wings extended perpendicular to the thorax. It appeared that those that had fed for longer periods also remained relatively inactive for long periods. This might suggest that the bees were affected by the paralysing neurotoxin coniine which is known to be present in the secretion (Mody et al., 1976) though it cannot be ascertained for certain.

Typically, flying insects, in particular flies, feed progressively from the lid, the underside of the lid, the column and then onto the margin of the pitcher

30 Julian Brook tube where through a combination of its waxy surface and the effect of coniine on their co-ordination they are prone to falling in. The bees were not observed travelling to the underside of the lid, the column or the lip of the pitcher. Equally, none were seen to fall into the pitcher tube. That is not to say any didn't enter the pitfall outside of the periods of observation. No pitchers were sectioned during the observation period to see if this is the case. Given the wide ratio of bees recorded to the number of plants, with each having approximately twenty pitchers, a comprehensive search would have been required in a specimen collection I did not want to destroy for that purpose. Subsequently on 2 April 2011, during the onset of Sarracenia dormancy, an investigation into the capture of Leioproctus was undertaken by sectioning 50 spent pitchers of the plants the bees were observed to have fed from and from those plants adjacent to them. No trace of Leioproctus was recognised among the hundreds of insects within the pitchers.

References Donovan BJ, Maynard GV. 2010 The New Zealand native bee Leioproctus (Leioproctus) otautahi Donovan (: Apoidea: ) is synonymous with Leioproctus (Leioproctus) launcestonensis (Cockerell) from Australia. New Zealand Entomologist 33: 17-18

Donovan BJ, Howlett BG, Walker MK. 2010 Relocation and establishment of nesting populations of the native bee Leioproctus huakiwi Donovan (Hymenoptera: Colletidae). New Zealand Entomologist 33: 109- 113

Mody NV, Henson R, Hedin PA, Kokpol U, Miles DH. 1976 Isolation of the insect paralyzing agent coniine from Sarracenia flava. Cellular and Molecular Life Sciences, 32: 829-830.