Entomology, hot and dry

A couple of weeks ago, I had the privilege of travelling to Malawi to assist with setting up some new activities on our ongoing Darwin Initiative and McKnight projects in Eastern and Southern Africa. Previous activities on the project had taken place in northern Tanzania, around the slopes of Mt Kilimanjaro, which is climatically quite an interesting place – the altitude means the evenings are pleasantly cool (bring a sweater!) and the higher elevation farms are really quite wet! Many of the fields were small, and edged on all sides by trees or other vegetation, with a fair few uncultivated margins and other patches of unused land all around. As a result, even between cropping cycles there was a huge amount going on in and around fields in terms of the biodiversity.

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Milkweed locusts are particularly striking. I asked if these were ever eaten (they are so enormous and numerous, it seemed like a pretty impressive protein resource going on), but apparently they have a foul smell/flavour and a greasy consistency, so people prefer the smaller grasshoppers, crickets and katydids for eating.

milkweed

(Incidentally, this one seemed to have some sort of parasitoid or entomopathogen – we saw a lot like this, the abdomen shrivelled, the legs clinging tightly to vegetation).

Also impressive in Tanzania was the diversity of pollinators – Xylocopa carpenter bees were extremely common and always spectacular, but we also came across cuckoo bees, little Amegilla, and a variety of tiny solitary and stingless bees. The project aims to evaluate how margin management can increase the abundance and diversity of pollinators further, so we’ve been gathering data about them and how they interact with wild plants as well as the crop.

Malawi is quite different. Around Lilongwe, the annual rainfall is really concentrated into a space of just a couple of months. When we visited, right at the end of the dry season, it meant that there had been next to no rain for about 9 months. It was relatively hot (exacerbated by the lack of shade), very dry and very windy – so also very dusty.The agriculture is different too, and brings new challenges. Farmers have to contend with the windiest part of the year also being the driest part – and the point in the cropping cycle when the fields are bare. Soil fertility suffers. Many of the fields have no margin at all – it’s literally crop after crop running right from the road at one side to a footpath at the other side, with fields demarcated from their neighbours by (if you’re lucky) a single tree or path.

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fields

Some of the sites do have nearby semi-natural areas, so we’re focusing on characterising the benefits derived from this in terms of pollinators and natural enemies. At this time of year, there weren’t a lot of either, but a few male Amegilla seemed to be patrolling a patch of Combretum we found, and of course there are always ladybirds to be found.

amegilla

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Some of the most fascinating areas were the graveyard sites. Because of the cultural importance, these patches of forest were left relatively pristine and untouched compared to any other woodland (which tended to be used for firewood and non-timber products) and so the plant and insect diversity in and around them could be extremely high compared to almost anywhere else in the landscape.

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