Because dragonflies and cicadas have the same legs.

Let's assume that all spiders are there.

Leg number 24*8= 192

The extra legs are because of dragonflies and cicadas.

Then you can draw the total number of dragonflies and cicadas as follows

( 192- 156)/2 = 18.

So there are spiders 24- 18=6.

The question becomes

Dragonflies and cicadas are a *** 18 with 108 legs and 28 pairs of wings.

Suppose they are all dragonflies.

The number of wings is

18*2=36

The extra wings are because of cicadas.

So the number of cicadas is

(36-28)/ 1=8 pieces

Then the dragonfly is 18-8= 10.

finally

Spider: 6

Dragonfly: 10

Cicada: 8