For your holiday pleasure or need for nerdiness: This relates to a recent story, but also any story with small or shrinking beings/characters. This is just biophysics, no magic used!   The first part was written for something else.

Another factor in insects' strength relative to dogs, humans,
etc. is a scale factor.   Muscle strength is dependent on its cross section
area, the same with the strength of insect legs, however weight/mass is
dependent on volume.   Area takes 2 dimensions, but volume takes 3 dimensions.
As a primary dimension decreases, area decreases with the square of this
dimension ie. decreases faster and volume decreases with the cube of this
dimension ie decreases even faster than area.   What we get is strength to
weight ratio much higher than in larger animals.   This is also seen in the
jumping ability of small dogs, usually many times their height, compared to
that of elephants or even large mastiffs like 90kg.   

Here is an example:

Heavyweight class weight lifter (college or Olympic, no steroids) weight 100kg, lifts 300kg (maybe just lifts to his thigh ie. "dead lift"); 0.3m^2 cross-section (estimated) muscle area; height 1.8m; max. width 1m; typical thickness 0.556m; representative volume 1m^3 (not his actual volume, just a number to follow); muscle strength/ area = 1000kg/m^2 . I think best womyn weight lifters lift 75% of best men's lifts.   

Reduce linear dimension á·10 => (all dimensions stay in same proportion) volume .18*.1*.0556 = 0.001; weight 0.1kg; xsec 3*10^-3 m^2; lifts 3kg ie. 10x stronger per weight.   

This continues, volume and weight decrease with the cube of the linear dimension, muscle cross-section and strength decrease with the square of the linear dimension. Another 10x decrease: height 18mm; weight 0.1gram; strength 30grams. Insect size weight lifter lifts 300x his own weight.