An interesting ladybug larva in Panama
LAST YEAR I WAS IN PANAMA to give a lecture (Introducción a los Laboulbeniales: hongos ectoparásitos estrictos de artrópodos) and to co-teach the international workshop “Hongos Asociados a Insectos”. Luckily, there was time to go in the field and look for insects. We went back to what has become my favorite collecting spot over the years: the abandoned orange plantation in Potrerillos Abajo. It is located at a crossroad opposite a small restaurant (talking about convenience with regard to lunch!) and faces the mighty Volcán Barú. To get inside, we have to climb over a fence. There constantly is a herd of cows, and I’ve also seen a number of (wild?) horses. The orange trees themselves are not being taken care of, they’re old, overgrown with lots of other plants. However, there are fruits on them, and I’ve tasted some every now and then and I totally approve! Great taste!
During these collecting trips at the abandoned plantation, we have found a number of insects infected with Laboulbeniales, the ectoparasitic fungi that I am interested in: globe-marked ladybugs (Azya orbigera) with Hesperomyces virescens, Systena sp. leaf beetles (Chrysomelidae) with Laboulbenia systenae, and Capraita sp. leaf beetles with Dimeromyces homophoetae (see this paper for details). On one of the branches of such an orange tree, I found an insect larva. First thing that crossed my mind was: “This could be Harmonia axyridis.” What a find!
Why is that? Well, Harmonia axyridis, the Asian multicolored ladybug, is an invasive species that has become a real pest. It was introduced to control aphids and scale insects, but over the years has become a thread itself to the native ladybug communities but also to fruit production and processing. Ladybugs of this species are feeding and aggregating on apples, pears, and grapes; when crushed they release an yellow, alkaloid-rich “reflex blood” that will affect the taste of these fruits (or of the wine in the case of grapes). For these reasons, H. axyridis has received a lot of attention by the scientific community the past few years (see here, here, and here). Although it is spreading all over the world, reports from Central America are unknown. And so I thought I might have found the first larva in Panama. (It always begins with a single specimen! In the Netherlands, a single pupa was found on a Hedera helix leaf in October 2002. This turned out to be the first report of H. axyridis in the county. Not even a year later, between July and September 2003, 34 H. axyridis adults were collected at another locality in the Netherlands. Harmonia axyridis had started spreading, and quickly!)
Back to Panama. I forgot about my larva. I did, until last week. I saw it floating around in its tube filled with 95% ethanol and I decided to remove a leg for DNA extraction. I sequenced the insect barcode (cytochrome oxidase subunit I) and I loaded my sequence onto the online sequence database GenBank, to compare it to millions of other sequences. Doing so, I was able to find out that my larva was not H. axyridis. Sad smiley face. Instead, it turned out to be Coccinella septempunctata, the seven-spotted ladybug. My first thought was “well, that’s disappointing,” only to realize seconds later that the seven-spot is an invasive species as well.
After digging into the literature, I came to find that this record of C. septempunctata in Panama is the first one for the country and by extension even the first one in Central America! Not so disappointing anymore!
A bit more about this species. Coccinella septempunctata is native to temperate Europe, North Africa, and Asia. It was introduced into North America between 1956 and 1971 as a biological control of aphids. However, the species has become established in the USA and Canada, where it can be found 100s to even 1000s of kilometers away from the original release site. The seven-spot was introduced in 18 US states, and currently is present in 31 states, covering the country from west to east. The reason for this successful invasion and establishment is that C. septempunctata is highly mobile and has a broad ecological plasticity, that is, it can thrive in many different habitats.
It may be puzzling that this ladybug successfully can live and reproduce under tropical conditions. However, it has been found under rocks in alpine tundra and on a snow field at 3,475 m a.s.l. (Rocky Mountains). To my current understanding, this record only confirms it being a generalist. It being a habitat generalist explains a lot. Also, since it is such an ecologically plastic species, the spread to more tropical areas has most likely been a gradual process. Therefore, we should be on the lookout for the seven-spot in New Mexico, Arizona, and California in the USA and in Mexico.
As a final note: this new Panamanian record shows that, in the background of the mass interest in H. axyridis, Coccinella septempunctata may be quietly increasing its geographic distribution. It’s important to follow up on this since this ladybug, as does H. axyridis, has such negative impacts at native ladybug community structures. It has also been reported to attack and even bite people. Ouch!