Allometry – What matters the larval growth?

2017.02.21.

I’m rearing couple of dynastine scarab beetles, and I checked up some larvae the other day. I found some interesting specimens. A group of larvae which hatched a lot earlier are still so tiny (still L1-L2), while the other group of larvae hatched later are fully grown up to L3 instars.

I had this experience of larvae not growing up enough in given time when I reared Dynastes grantii Horn. This time, both Strategus aloeus (Linnaeus) and Dynastes tityus (Linnaeus) shown the results. In this post, I’ll be posting two pictures of two groups of S. aloeus (Linnaeus) only.

When I first reared D. grantii larvae, I fed horribly fermented substrate and they took such a long time to grow up. With several months, they were still L1-L2. At the time, since I knew I fed them bad food, I thought that was the cause. Then later years, I tried to rear them again and fed really good substrate with well fermented oaks. Larvae grew up so fast and reached L3 instar within a month. So obviously, at the time, I thought larval growth surely matters with the food quality.

When I faced trouble again the other day with S. aloeus, I actually asked couple of my friends, and found the right answer to this issue. Larval growth usually matters with an activity space. With enough space, each larva will eat up the food and moves around.

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Above is a picture of a group hatched a lot earlier than below. They are still all in L1-L2 instar. They were picked up as eggs on October 11th, 2016, and hatched as follows. Eggs were kept in 16.6 fl oz. (490.9cc) container since then and only one or two larvae survived.

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Five larvae here are kept in 230.4 fl oz (6813.74cc). These larvae were laid as eggs after Oct. 11th, 2016, as female was still alive for couple of weeks. The container they were kept is the container for adult beetles to lay eggs. There is a significant difference in larval growth in size of container they were kept, or ‘the activity space.’

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