Weevil News

http://www.curci.de/Inhalt.html

No. 16

10 pp.

20th November 2003

ISSN 1615-3472

Stüben, P.E. (2003): The Rediscovery of Acalles droueti Crotch 1867 and Curculionoidea collected on an excursion on the Azores: A Report. (Coleoptera: Curculionidae: Cryptorhynchinae) - Weevil News: http://www.curci.de/Inhalt.html, No. 16: 10 pp., CURCULIO-Institute: Mönchengladbach. (ISSN 1615-3472).

The Rediscovery of Acalles droueti Crotch 1867
and Curculionoidea collected on an excursion on the Azores:
A Report*
(Coleoptera: Curculionidae: Cryptorhynchinae)
by
Peter E. Stüben, Mönchengladbach
with 36 figures

Abstract
Acalles droueti Crotch 1867 was rediscovered in Euphorbia stygiana on the islands of Pico and Faial during a trip to the Azores in the summer of 2003. The biology, ecology, and habitat requirements of these species are described. A list of Curculionoidea that were also collected and new finds is given in the Appendix.
Key Words
Coleoptera, Curculionidae, Cryptorhynchinae, Acalles droueti, biology, ecology, host-plant, Euphorbia stygiana, Portugal, Azores.

Introduction
I received syntypes of Acalles droueti Crotch 1867 from the Natural History Museum in London in November 2002. In connection with my work on the Second Analytical Catalogue for Cryptorhynchinae [Stüben, Behne & Bahr 2003: 32], I designated lecto- and paralectotypes (of the the species) and photographed its habit and aedeagus with a high-resolution digital camera. [Fig. DR27][Fig. DR29] This work convinced me that I wanted to document, for the first time in 130 years, the presence of this Cryptorhynchinae in the Azores, without a doubt the most beautiful Cryptorhynchinae of the western Palaearctic region. The information available about this unusual species in the western Palaearctic was anything but encouraging. The only thing that was said the first time it was described was "Hab. in ins. Flores intra euphorbiam emortuam sat copiose lectus" [Crotch 1867]. Israelson mentioned only that this species and a few other endemic species had apparently not been found in the previous hundred years. [Israelson 1990: 7]

I visited the Azores from July 31 to September 2, 2003, spending a week each on the islands Terceira, Flores, Pico, Faial and São Miguel. I was very hospitably received by Paulo Borges of the University of Azores – Dep. of Agriculture on Terceira (Angra do Heroísmo). [Fig. DR30] I was permitted to work in his laboratory, received access to the collections, and received considerable useful information about the possible occurrence of the host plant, Euphorbia stygiana Wats., on Terceira and Flores. It was one of the most difficult, but also one of the most successful excursions I have made in the last several years.

Logistics, Methods, Disappointment
First, the area of possible occurrence of the host plant had to be defined. In one regard, G.R. Crotch could not be mistaken: The six syntype specimens (5 male/1 female) were immature, i.e., they had to have been taken from within a branch, and cannot have been ‘guests’ - occurring only occasionally in a dead branch of a Euphorbiaceae. Adult Cryptorhynchinae are known to remain in the host plant for several weeks after emerging from the pupa [Stüben 2003b]. The question was only which Euphorbiaceae did Crotch find them in 1867. Without a doubt, the immigrants from North America were to be excluded: Euphorbia maculata L. (all islands except Corvo), Euphorbia nutans Lag. (Faial) and Euphorbia marginata Pursh. (Santa Maria, Faial). I concentrated on the two endemic species Euphorbia azorica Seub. (all islands) and Euphorbia stygiana Wats. [Schäfer 2002]

Acalles droueti has very long legs, typical of the known species of the laurel forests of the Canary Islands and Madeira. Moreover, the narrow habit with long bristle tufts on the elytra are similar to the species that live in trees on all of the Moroccan islands, which I have described and redescribed in numerous publications over the last several years. [Stüben 2000e][Stüben 2000k] [Stüben 2002] Because the species can get to be 5.5 mm across, Euphorbia azorica [Fig. DR1], a low, herbaceous plant in coastal areas below 100 m elevation, could not be the host plant. A very good possibility was Euphorbia stygiana [Fig. DR2], which grows as high as 5 m and prefers the same habitats that the tree-like Euphorbia mellifera Ait. on Madeira [Fig. DR3] and several of the Canary islands. It is – or better was – a regular part of the laurel forests of the Moroccan islands, growing in canyons, volcano craters, and in the moist habitats of the laurel-juniper forests continually wrapped in fog. [Sjögren: 2001].

On Terceira and Flores, this first hypothesis led to disappointment. I found eight living [Fig. DR4] and one dead Euphorbia stygiana [Fig. DR5] in a small crater (Pico Gaspar) near the lake 'Lagoa do Negro' east of the Serra de Santa Barbara mountains on Terceira. In vain! The site at which I found this rare and endangered plant was much too isolated for Acalles droueti to be present, the plants were no higher than 1.5 m, and Azorean laurel forests were nearly completely absent, which was certainly due to anthropogenic influences – clearing and occasionally grazing. [Fig. DR6] The same situation was found on Flores, the type location. I found five plants in a steep-sided valley southwest of Ponta Delgada. [Fig. DR7]. I was able to take larva, pupa, and adult specimens of Rhopalomesites tardyi (Curtis 1825) from the dead branches, but the site was immediately adjacent to a bridge built only a few decades ago, so the plants could not be very old. Upstream from the bridge I found no further Euphorbia among the hydrangea (Hydrangea macrophylla (Thunb.) Ser.), with its dense root system, and Pittosporum undulatum (native to southeast Australia), the greatest threat for the remainder of the endemic Azorean flora. There was some hope when I discovered – in the nearly completely deforested island interior, except for a few resistant junipers – a relatively large occurrence of Euphorbia stygiana [Fig. DR8] at the bottom of the steep crater Lagoa Seca, 60 m below the crater edge. But for me it was unreachable without a rope or alpine experience.

Difficult search on Pico
Relatively large stands of Euphorbia stygiana were found only on Pico, the third island of my trip. [Fig. DR9] A large group was found on August 18, 2003, at the side of the road EN3 across Pico volcano, which rises to an elevation of 2351 m on the north side of the island. The specimens were up to 5 m high, some of them uprooted by the stream at high water, some of them dying. They were in a residual Laurus forest with the typical bush and tree species of this kind of forest: Laurus azorica (Seub.) Franco, Vaccinium cylindraceum J.E. Sm., Erica azorica (Hochst.) D.A. Webb, Ilex perado Ait. ssp. azorica Tut., Viburnum tinus L. ssp. subcordatum (Trel.) P. Silva, Frangula azorica V.Grubow and – of course – Euphorbia stygiana.

Standing in the wet roadside ditch, I cut open dead or dying branches and roots for hours and – initially just as unsuccessful – sieved through the leaves and twigs on the ground. Perhaps Crotch did mean the coastal Euphorbia azorica, which prefers a distinctly drier habitat.

At the base of the large Euphorbiacae, I was reminded of a situation years ago in the primary laurel forests of central Madeira ("Folhadal"). Christoph Bayer from Berlin and I had searched unsuccessfully for days for Acalles cinereus Wollaston 1860 under Euphorbia mellifera trees up to 12 m high. [Fig. DR10] [Fig. DR28]. We finally found larvae, pupae, and immature specimens at the ends of dead branches in the top of the trees [Fig. DR11] [Fig. DR12], confirming Wollaston's description of the host plant after 140 years. [Stüben 2002] Climbing these Euphorbiaceae, which bent from their own weight, was not particularly safe, and the white latex sap, toxic to insects [Sprick & Stüben 2000], oozed out from the slightest injuries to the plant, sticking to clothes and hair, was quite unpleasant. The search on Pico for a highly specialized insect which avoided the toxic sap by living only in dead plant parts became increasingly more difficult.

It is difficult to describe the blissful feeling that I had when, more than 130 years after it was first described, I found larvae, pupae, and immature specimens of Acalles droueti in the dead, hollow branches at the top of this endemic Euphorbia. [Fig. DR13]. The dead, dark-colored leaves at the top of the tree contained dozens of these uniquely colored Cryptorhynchinae. [Fig. DR14]

On the same day, further Acalles droueti were found in Euphorbia stygiana at the intersection of the road EN3 with the EN2, where plants with a diameter of 20 – 35 cm at the base stood in a depression. I had already unsuccessfully knocked on these plants in my search. The insects retreat into the dead ends of the branches of the crown during the day. Even the most severe storms are not able to injure them in this refuge, so it is not surprising that they haven't been previously knocked out of their dead, hollow branches by entomologists. If the dead, bleached branches can be reached and broken off, the larvae, pupae, and immature specimens can be collected so that the eating behavior of the larva, the making of the pupal chamber and the emerging from the pupa can be observed.

(While I am writing this during the late hours, specimens of this species are copulating in my insectarium on my desk. The eggs are deposited on a dying Euphorbia stygiana branch about 30 cm long. I am optimistic that within a few months I will be able to describe all phases of development – eggs, larvae, and pupae – in SNUDEBILLER...)

Discovered today, described tomorrow, and extinct day after tomorrow?
I found Acalles droueti at only two other places on Pico. [Fig. DR 34] The largest occurrence of the host plant Euphorbia stygiana was at the foot of the east side of Pico's highest volcano, Pico da Urze (899 m). Specimens of this Euphorbiaceae grow in the relatively small crater, especially on the steep, north-facing slopes, often forming large stands of tall trees. Large numbers of Acalles droueti were found in the ends of hollow, bleached branches of tall plants in a deep gulch. The dead branches in the crown, towering above the roof of the forest, could be "harvested" from the edge of the gulch. I also used this method at a small crater (Cabeco das Rochinha) in the easternmost part of Pico that I found using my knowledge of the ecological niches of Acalles droueti. During the day, it retreats only into absolutely dry, hollow, thick-walled, about 1 cm thick branches of Euphorbia stygiana in very old stands at extremely humid sites protected from the wind. The plant prefers locations on the steepest slopes just below the rim of the crater, from where – with some daring and dexterity – the insects can be collected.

Of course, after finding this easternmost discovery site, not far from the town of Calheta de Nesquim on the coast and the large occurrence at the foot of Pico da Urze, I made every effort to find all occurrences of Euphorbia stygiana to determine whether they contained populations of the flightless Acalles droueti. But in the interior of the island between the coastal towns of Lajes do Pico and Prainha, I found no weevils during a three-day search in the "Reserva Florestal Natural da Lagoa do Caiado". In this area on only a few hectares there is a residual primary laurel forest in thick beds of Sphagnum moss. In the branches of this – surely the most beautiful and least affected by anthropogenic influences – stand, I found only Tarphius depressus Gillerfors (Col., Colydiidae; P. Borges det.), although the Euphorbia stands were very old. Even on Pico, the Azorean island least affected by humans, all of the relict laurel forests between 600 and 900 m are separated by km-wide pastures (subsidized by the EU funds for regions at the EU margin) [Fig. DR15], the Cryptomeria japonica plantations are being expanded at an unbelievable rate [Fig. DR16], and a "green desert" has been created by the often "unintentioned" introduction of new plant species from all parts of the world: Pinus pinaster (southwestern Europe), Cryptomeria japonica (Japan), Hydrangea macrophylla (Japan), Pittosporum undulatum (southeastern Australia, up to 600 m), Hedychium gardnerianum (Himalaya). Sphaeropteris cooperi (Australia) and Eucalyptus globulus (Tasmania) are only some examples of a nearly complete change in the flora of the Azores. Hundreds of other introduced plant species could be named that have brought the very sensitive endemic island flora to the edge of extinction.

The nature preserve on the lake "Lagoa do Caiado" on Pico is no exception to this development. The protective fences are torn down to allow cattle to graze in the forest; EU-subsidized road construction is replacing the dusty trails with wide asphalt highways that go through the middle of nature preserves of only a few hectares, promoting tourism into the most remote corners of the island. [Fig. DR17]. Small craters are opened to grazing, serving as a natural corral; the rims of large caldeiras are removed so that the interior can serve as a wind- and weather-protected pasture. [Fig. DR18]

I made every effort to find the last relicts of laurel forests in the craters on Pico and found only small stands of Euphorbia stygiana. For days I examined laurel stands on the pastures – each only several meters square – between Pico da Urze and Lagoa da Capitao. [Fig. DR19] The elation I experienced with the rediscovery of Acalles droueti was increasingly overlain with disappointment. I still find it difficult to suppress my anger about this extreme case of "ecocide", unparalleled anywhere else in the world. Acalles droueti is an example that shows the existence of the host plant is not sufficient if the microclimate and microecological conditions are not present. The species prefers an extremely moist site. It will leave the dead branches and leaves only if the humidity between a dense forest roof and a thick Sphagnum bed is high enough. This is shown by the first breeding attempts (see SNUDEBILLER 5/2004). Under the present conditions on the island, the fall and winter winds blow unhindered through the islands of laurel flora on the extensive pastures, the trampling of the soil increases drainage, causing the islands of laurel to gradually dry out during the hot summer months of little rain. What remains are tree skeletons [Fig. DR20], and the nearly certain prediction that the four sites at which Acalles droueti and Euphorbia stygiana have been identified on Pico will not be sufficient to stop the fragmentation of the populations which prevents genetic exchange between the subpopulations. This is not only the case for these two species, but for all other endemic, highly specialized phytophagous insect species with a rather narrow ecological niche, as I have already demonstrated on the Madeira Islands. [Stüben 2002: 158-168]

What remains is the Caldeira do Faial Nature Reserve…
For an entomologist, the highpoint of any trip to the Azores is the large Faial caldeira, which today is part of the Caldeira do Faial Nature Reserve and still contains a largely autochthonous flora and fauna [Fig. DR22]. I received all of the information I needed from Eng. João Melo, the Director of the Faial Botanical Gardens, who was able to give the exact locations of many of the endemic species. It was only a question of the weather when I could visit the caldeira, which has a nearly 400 m high rim and is about 1.5 km across. [Fig. DR21]

Euphorbia stygiana occurs in large stands on the inside of the northeastern rim about 100 – 250 m below the rim. The katabatic winds and steep slopes have created a creeping form (up to 6 m long) of the species. [Fig. DR23] As on Pico, Acalles droueti was not found in the numerous dead branches on the ground. Larvae, pupae, and immature specimens were found, however, in the dry stems just below the tree crowns above Sphagnum beds up to 80 cm thick.

The Cabeco Gordo at the rim of the Faial caldeira reaches an elevation of 1043 m, and except for the southwest side the caldeira is used only for cattle raising and forestry. [Fig. DR24] The pastures and Cryptomeria forests end at the caldeira rim, along which there is a 5 m wide Hydrangea macrophylla hedge. Unfortunately, I found that the hydrangeas – which the tourists love and are viewed as a plague by those seeking to protect the endemic environment – have found their way along streams in the interior of the caldeira [Fig. DR25]. These Hydrangeaceae from Japan occupy the same habitats along the streams as Euphorbia stygiana, which cannot compete with it.

…and promotion of active environmental policies on the Azores
This report on the rediscovery of Acalles droueti on the Azorean islands of Pico and Faial should end here. But I would be negligent as an entomologist, and even more so as a taxonomist, if – in my enthusiasm about finding a species long thought to be extinct – I did not reflect on the further survival of this unique Cryptorhynchinae (there is considerable discussion at the CURCULIO Institute about which genus it should belong to). What would be the sense of such an excursion, what would be the value of the new description of this species, if it was not accompanied by criticism of the lack of environmental protection on the Azores?

The NATURA 2000 project [Fig. DR31] and the preservation of endemic flora and fauna on the Azores has been discussed in numerous governmental publications at the EU and national levels. [Fig. DR31a] These environmental protection policies are surely necessary if we will be able to hand on the remaining autochthonous flora and fauna to the next generation. But I have my doubts that the "philosophy of conservation" and "conservation management schemes" behind these policies will be effective enough. The areas worthy of being preserved on the nine islands of the Azores – except for the Faial caldeira – generally consist of only a few hectares, are not part of any network of habitats [Borges et al.: in print], and therefore for many arthropods (but not birds) are tiny enclaves in a sea of uniform pastures and tree plantations. In view of this fragmentation and the fact that there is a threshold below which a micropopulation cannot survive, it must be allowed to question whether policies limited to protection and conservation are sufficient. The question must be allowed whether it is not better to undertake an active policy, for example, to rejuvenate the destroyed flora in the craters: to not only remove foreign flora from the nature reserves, but reintroduce the endemic flora, which is well known to have been there originally – to return to the Azores what we have taken from them over the last several centuries and decades.

For me, it is (also) important to save the species Acalles droueti Crotch 1867 from extinction. It is one thing to provide professors and students on the Azores with the funds need to study the microecological requirements of the species along a well-selected transect. This is absolutely necessary for serious scientific work. But it is just as important to apply this knowledge. Why not begin with the reforestation of the many small, damaged craters on Terceira, Pico, and the other islands, with the reintroduction of endemic flora. For example, students could carry out such work, and politicians and others could sponsor individual craters. That would be a beginning. But – in contrast to most parts of continental Europe or on the other Portuguese islands in the Atlantic – is there any other alternative in the "green deserts" of the Azores?! [Fig. DR26]
* The scientific results, description, and redescription of new Cryptorhynchinae, the description of larva and pupa, as well as raising the next generation – if successful – of Acalles droueti, will be presented in SNUDEBILLER 5/2004.

Appendix 1
The data on the findings of Acalles droueti Crotch 1867 during my excursion to the Azores [Fig. DR34]
All new records based on [Borges 1990: Table II.]

After completion of this report, I received two further specimens from my colleague Paulo Borges (Azores: Terceira), belonging unambiguously to Acalles droueti Crotch 1867. It should be noted that Isabel Amorim and F. Pereira, a student and a technician of P. Borges, collected in 2001 altogether 12 specimens of Acalles droueti at Cabecinhos (Pico) when sampling Tarphius spec. on Euphorbia stygiana, being the specimens only recently rediscovered among stored samples when F. Pereira saw a picture of the species sent to P. Borges by me.

New records for Pico and Faial!


Appendix 2
The data on the findings of Curculionoidea specimens during my excursion to the Azores (identified by Lutz Behne of Eberswalde, DEI (German Entomological Institute), Germany)
All new records based on [Borges 1990: Table II.]
Aspidapion radiolus chalybeipenne (Wollaston 1854)

Caenopsis waltoni (Boheman 1843) [Fig. DR32]

New record for the Azores (from Madeira or Western Europe)!

 

Cathormiocerus curvipes (Wollaston 1854)

New record for Terceira!  


Gymnetron pascuorum (Gyllenhal 1813)

New record for Terceira!

 

Naupactus peregrinus (Buchanan 1939)

(= Graphognathus)

Otiorhynchus cribricollis Gyllenhal 1834

(= O. trophonius var. azoricus Uyttb. 1940)

New record for Flores!

Otiorhynchus parvicollis Gyllenhal 1834 [Fig. DR33]

New record for the Azores (from Portugal or North Africa)!

 

Otiorhynchus sulcatus (Fabricius 1775)

Pantomorus cervinus (Boheman 1849)

(= Asynonychus godmanni (Crotch 1867), godmani auct. err.)

Pselactus spadix (Herbst 1795)

New record for Terceira!

 

Pseudechinosoma nodosum Hustache 1936

Endemic  


Pseudophloeophagus aeneopiceus (Boheman 1845)

Pseudophloeophagus tenax (Wollaston 1854)

Rhopalomesites tardyi (Curtis 1825)

New record for Terceira!

 

Sitona puberulus Reitter 1903

Tychius cuprifer (Panzer 1799)

References

Borges P.A.V. (1990): A checklist of Coleoptera from the Azores with some systematic and biogeographic comments. – Boletim do Museu Municipal do Funchal, 42 (220): 87-136.

Borges, P.A.V., Aguiar, C., Amaral, J., Amorim, I.R., André, G., Arraiol, A., Baz, A., Dinis, F., Enghoff, H., Gaspar,  C., Ilharco, F., Mahnert, V., Melo, C., Pereira, F., Quartau, J.A., Ribeiro, S., Ribes, J., Serrano, A.R.M., Sousa, A.B., Strassen, R.zur, Vieira, L., Vieira, V., Vitorino, A., & Wunderlich, J. (in print): Ranking protected areas in the Azores using standardized sampling of soil epigean arthropods. Biodiversity and Conservation

Israelson G. (1990): Further notes on the Coleopterous fauna of the Azores, with speculations on its origin. – Bocagiana (Madeira),138: 1-8.

Schäfer H. (2002): Flora of the Azores. A field Guide, Weikersheim, 264 pp.

Sprick P. & Stüben, P.E. (2000): Ökologie der kanarischen Cryptorhynchinae außerhalb des Laurisilva. - in: Stüben, P.E. (2000b), SNUDEBILLER 1 (CD ROM): 318-341, Mönchengladbach.

Stüben P.E. (2000e): Die Arten des Genus Acalles von den Kanarischen Inseln. - in: Stüben, P.E. (2000b), SNUDEBILLER 1 (CD ROM): 22-98, Mönchengladbach.

Stüben P.E. (2000k): Phylogenie der endemischen Taxa des Genus Acalles von den Kanarischen Inseln. - in: Stüben, P.E. (2000b), SNUDEBILLER 1 (CD ROM): 287-292, Mönchengladbach.

Stüben P.E. (2002): Die Cryptorhynchinae von den Inseln Madeiras und Salvagens. Taxonomie, Bionomie, Biogeographie und Evolution. (Coleoptera: Curculionidae). - SNUDEBILLER 3, Studies on taxonomy, biology and ecology of Curculionoidea, Mönchengladbach: CURCULIO-Institute, 88-195.

Stüben P.E. (2003b): Breeding of Kyklioacalles euphorbiophilus Stüben 2003 (Coleoptera: Curculionidae: Cryptorhynchinae) - Weevil News: http://www.curci.de/Inhalt.html, No. 15, CURCULIO-Institute: Mönchengladbach: 6 pp.

Stüben P.E., Behne, L. & Bahr, F. (2003): Analytischer Katalog der westpaläarktischen Cryptorhynchinae / Analytical Catalogue of Westpalearctic Cryptorhynchinae. Teil/Part 2: Acalles, Acallocrates (Col.: Curculionidae: Cryptorhynchinae). - SNUDEBILLER 4, Studies on taxonomy, biology and ecology of Curculionoidea, Mönchengladbach: CURCULIO-Institute.

Sjögren E. (2001): Plants and Flowers of the Azores, Azores: Lajes do Pico, 191 pp.

Address:
Dr. Peter E. Stüben
CURCULIO Institute
Hauweg 62, D- 41066 Mönchengladbach, Germany
E-Mail: P.Stueben@t-online.de