bigger size does not means for better advantages. Small size of insects is a typical evolutionary benefit for insects to enjoy different food habitats and environments. it also varies on the socialization or solitary nature oft the insects. For example, honeybee queen has potential to produce thousands of offspring in her life, bumblebees produces a few hundred, flies and butterflies and moths may produce from a few hundred to a few thousand. This shows a great variation depending on the system in which that in sect belong. this is also the aspect of their success for competition against human beings

Dear Prakash,

At the University of Florida you can find in 40 chapters the highest insect performances and tolerances. It seems to me that there are no correlations between these performances and body size.

Unversity of Florida, Book of Insect Records

http://entnemdept.ufl.edu/walker/ufbir/chapters/index_order.shtml

This is a tricky area of discussion. Some insects display agonistic behaviours supported by modifed body parts. A classic example is the horn of stage beetles or the eye-stalks of Diopsidae and related families of flies. Butting and measuring-up have been observed in these groups, usually with the large male winning the harem of females and gaining reproductive advantage. Furthermore, in flies, adult size can be dependent on quality and quantity of larval food resources, leading to larger specimens if such resources are abundant and smaller specimens as the quality and quantity of larval food resources tails off. The large specimens emerging earlier have a reproductive advantage over the smaller ones emerging later in the sequence.

On a boarder taxonomic platform, Munir and András are correct though. Minute Parastica wasps (e.g. some of the smaller Mymaridae) are at no less an advantage compared to the larger Dynastinae (Rhino-beetles) and indeed the largest ever insects are already extinct. So I think it depends on whether the question is asked 'within-taxon' or 'between-taxa'.

Dear Andrew,

You are right. This is really a tricky area. However, I would say that adult size depends on the quality and quantity of larval food not only in case of flies but also in case of other (not only holometabolous) insects. And also the temperature may have an important impact on the development and body size. I reared Chrysopa septempunctata individuals and the lacewing larvae reared at higher temperature developed quicker but their body size was smaller and as well as their fitness. Thus, the earlier emergence of these insects did not contribute to their success.

That's interesting! Yes, I think the growth -food resource phenomenon is more widespread - but I kept to flies as its the taxon I'm more familiar with. Do you know - does that developmental temperature vs size hold true in wild populations? In other words can we expect specimens of Chrysopa septempunctata from more southern latitudes to be smaller than those from further northern (or over an altitudinal range)?

Such effects probably led to the evolution of gigantism in some fossil insect groups, especially meganisopterans, a Carboniferous to Permian group of odonate relatives, and titanopterans, a Triassic group of orthopterans.

There are many studies which discuss factor limiting body size throughout the evolutionary history of insects, see e.g.

http://www.pnas.org/content/109/27/10927.abstract

http://onlinelibrary.wiley.com/doi/10.1111/j.1502-3931.2008.00094.x/abstract

Dear Andrew,

I have collected Chrysoperla affinis in Scotland, Belgium, Hungary and Spain (Andaluzia). Regarding the samples from Scotland, Belgium and Hungary I have not observed size differences (I have not measured them), however in case of the Spanish individuals I have noticed clearly that they were smaller than the adults of northern populations. I stress investigation of size differences was not my aim I only perceived this phenomenon.

Dear Prakash, B. M.

it is important but rather broad question I would say.

First note that the answer might depend if you deal with intra or interspeciphic comparisons.

Secondly you might look at these issues from evolutionary perspective and find out that there are more moderately small bodied insects; but you can look at this question from more ecological perspective and discover that it depends on the context. So there should not be one answer. If you take abundance as a measure of fitness than you will see that smaller insects are generaly more abundant but there some peculiar exceptions e.g. carabids studied by us https://www.researchgate.net/publication/232724744_Local_and_regional_interspecific_abundance__body_weight_relationships_of_ground_beetles?ev=prf_pub

Overall there is very large literature dealing with body size in insects

here are two examples

http://onlinelibrary.wiley.com/doi/10.1111/j.1469-185X.2009.00097.x/abstract;jsessionid=B70F4FF5918B18506AC439257B381EE1.f04t04?deniedAccessCustomisedMessage=&userIsAuthenticated=false

or

http://www.home.umk.pl/~ulrichw/Publications/Oikos2006b.pdf

but do not be discouraged, good luck

Article Local and regional interspecific abundance – body weight rel...

I think the answer is that the bigger body sized increased adaptation and hence, fitness, in the particular ecological-evoloutionary circumstance of the organisms in question. Yes, size can be related to fecundity and number of offspring. But it can also be related to other factors, e.g. predation pressure. Having smaller bodies has an obviousadvantage in certain environments (e.g. many small-sized insects can explore a distributed resource better than a few large ones). You should check out the enlightening book by Peters; "The ecological implications of body size" and also literature on life cycle histories.

There is plenty of literature from Partridge and others (e.g., http://www.sciencedirect.com/science/article/pii/S0003347283802425) on body size in Drosophila and fitness in terms of mating success. In the above study, larger males enjoyed a higher lifetime mating success than smaller ones. Is bigger better?