Insects on cones

Insects frequenting male cones and eventually female cones during the pollen production are not many. They are mainly Coleoptera. Oberprieler (2004a) has summarized our knowledge about the cycad-associated weevils.

The idea of anemophilous pollination of cycads comes mainly due to an analogy with Coniferae. A male cone can produce enormous quantities of pollen, up to 100 cubic cm for Cycas circinalis cones. Actually, except for Cycas, the cones are firmly closed, and it seems difficult that wind alone can allow the pollen to enter into the micropyle, often situated several centimeters down inside the cone itself. With a few exceptions, only the entomophile solution, rarely observed, seems possible. Often weevils seem involved in this, as mentioned by Rattray (1913), in South Africa in cases of Encephalartos altensteini Lehm. and E. villlosus Lehm. Species of the genus Phlaephagus visit first the male cones, then visit the female cones. Doing that they fertilize them. According to the same author, Strangeria kaat%eri would be, on the contrary, exclusively anemophilous, which should be the reason why the cones of that plant do not produce heat.

Zamia furfuracea L., in Mexico, is pollinated by the weevil Rhopalotria mollis. Zamia pumila L. in Cuba has two pollinators, and also Zamia floridana A.D.C. (=integrifolia L.), in Florida, the male cones of which are visited by Rhopalotria slossoni and by a Langurid, Pharaxonota %amiae. Larvae and adults of these beetles feed in the male cone tissues and get covered with pollen. These insects get attracted by the female cones, probably by the heat produced by the cones and their specific odour. In a recent paper (Norstog et al, 1992), pollination of various Zamia has been detailed.

Dioon califanoi in Mexico (Vovides, 1991) is pollinated by various species of Pharaxonota. These langurid beetles (actually for some people: erotylids) frequent equally the male and female cones of Cerato%amia in Mexico. In Costa-Rica, in La Selva, several Pharaxonota frequent the male cones of Zamia skinneri Warsz. There are also, sometimes, on Zamia cones Lepi-doptera eggs larvae or pupae, including those of Lycaenidae (Eumaeus spp.), which feed on the fronds.

In Australia, the cycads Macro%amia communis and Tepido%amia peroffskyana are associated with the weevil Tranes lyterioides, a big noctural species, which develops inside male cones and eats the pollen. Many other beetles are associated with male cones of Cycadales, viz. Tenebrionidae, Rhizophagidae, Languridae, Anthribiidae, Boganiidae, and Nitidulidae. Other insects frequent male cones of cycads, like Trigona bees, a genus known from the Cretaceous, suggesting a very ancient association.

In Costa-Rica, Gomez has observed and photographed in Wilson Botanical Garden quantities of langurids, probably some Pharaxonota, invading the male cones of Zamia fairchildiana Gomez, devouring the starch. Those small brown beetles could be easily confused with Aulacosce-lis melanocera Stal or A. costaricensis Bechyne, if it was not for their much smaller size.

Crowson (1981, 1989, 1991) has pointed out that certain beetles frequent specially the cycad cones, namely the Boganiidae, dating from the lower Cretaceous and linked with Australia and Africa, then loosely connected, as suggested by the Gondwana Hypothesis. In South Africa, it is a Boganiid, Metacucujus encephalarti, which pollinates Encephalartos lunatus, and, in Australia, Paracucujus rostratus, which is met with on the male cones of Macro%amia riedlei (Endrody-Younga and Crowson, 1986).

Brentids of the genus Antliarrhinus breed inside the ovules of Encephalartos in Africa, and feed on the almond. Antliarrhinus %amiae digs with its rostrum through the sporophylls and ova, and lays, with its telescopic ovipositor, its eggs inside the cones of Encephalartos longifolius and E. altensteini. Antliarrhinus signatus comes directly inside the cone to lay its eggs (Oberprieler, 2004b). Crowson (1989) mentions many other curculionoids attacking cycad male cones, namely the genera Porthetes and Amorphocerus (both Cossoninae) in

Southern Africa. According to Crowson, many beetles, supposed to be cycad pollinators, possess in their mandibles cavities used to carry pollen grains. Others, such as the Allocorynidae and certain Curculionidae, have antennal cavities, perhaps for this purpose.

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