**8. Termite as bioindicator**

Termites are detritivorus insects that feed on debris of plant and about 75% feed on soil [48]. These social insects are used as bioindicatiors of land fertility and provide basis of nutrient recycling, nitrogen fixation and transport of soil material. Likewise, expansion of carbon content, nutrient and clay they are also considered as ecological engineer. Aljama *et al*. (2019) assessed accumulation as regard to various metals (mercury, lead, chromium, cadmium, zinc and copper) in termites along with associated soil [49].

### **9. Butterfly as bioindicator**

Butterflies are prominent bioindicators of ecological and metal pollution due to their easy recognition, conspicuous nature and capacity of accumulating heavy metal from surroundings. Kobiela and Snell- Rood [50] indicated the presence of transgenerational effect of nickel contamination in butterfly [50]. Azam *et al*. [51] had assessed the various heavy metals (Ni, Cu, Zn, Cr) accumulation in butterfly *Danaus chrysippus* near industrial areas of Gujrat and concluded as good indicator of metal pollution [51].

### **10. Dragonfly as bioindicator**

Ecologically dragonfly is considered as useful bioindicator of aquatic and terrestrial environment. Ninety percent of invertebrate fauna comprises of aquatic insects representing the lotic and lentic food web, controlling nutrient cycle and energy flow [52]. Dragonflies are considered as the most susceptible to habitat disruption among aquatic insects. Noor *et al*. [53] demonstrated iron as suitable indicator for the lead, iron and zinc where iron showed positive association of species richness with sediments whereas negative relation when iron detection in water [53].

### **11. Housefly as bioindicator**

Housefly (*Musca domestica*) is a philanthropic species and thus shows intimate association with humans and their surroundings. The housefly is a cosmopolitan insect, and a significant human and animal sanitary pest. It is the mechanical carrier of over 100 pathogens that include the antibiotic resistant ones [54]. Heavy metals like zinc, cadmium, copper, lead usually accumulate in the abdominal tissues of housefly [55]. The digestive tract injury had been reported due to accumulation of cadmium in larvae of housefly [56] however minimum concentration of cadmium has less effect on development and growth of housefly. Furthermore, the effect of cadmium on metamorphosis had been stated that showed dramatic variation as cadmium level gradually increased during larval phase but reduced dramatically following pupariation.

### **12. Parasitic wasp as bioindicator**

Parasitic wasp had been devoted as bioindicator of woodland environment [57] due to certain biological characteristics and feeding habits [58]. Their habitat conditions are specified and intricated as they appeared higher in tropic level, restricted host dimensions and complex behavior [59]. Aguiar *et al*. [60] reported 103,000 species of hymenopteran including 70% as parasitic wasp operating as pest of agriculture [60]. Lead concentration was found in fecal mass of wasp larvae as stated [61].

### **13. Analytical procedure of heavy metal assessment in insects**

These are the following analytical procedure of heavy metal assessment in insects reported by different authors.

*Recent Advances in Evaluating Insects as Bioindicators of Heavy Metal Pollution DOI: http://dx.doi.org/10.5772/intechopen.110212*

### **13.1 Atomic absorption spectrophotometer**

### *13.1.1 Graphite furnace and acetylene flame*

Azam *et al*. [51] had demonstrated the chemical procedure of determining the heavy metal in different group of insects [51]. Insects were weighed after manually dried in oven and digested in solution of four ratios of percholric acid to one ratio of supra pure nitric acid. A PU 93090X graphite furnace and acetylene flame of atomic absorption spectrophotometry was utilized to assess various metal concentrations of insects.

### *13.1.2 Electrothermal atomic absorption spectroscopy*

Using a microwave, 1.5 mL of nitric acid (2.5 percent) and 430 micro liter of hydrogen peroxide (30 percent) and 570 micro liter ultrapure water were applied to honey samples of honey bee atleast 0.6 g for determination of toxicity analysis as stated [44]. Following the digestion, the solution was mixed with one percent of Triton X 100 to reduce the viscosity before transferring it to the 25 mL flask. For the quantification of cadmium and lead, samples diluted with ultrapure water to 25 mL for chromium or 1 percent nitric acid and 3.30 micro liter of magnesium nitrate. The heavy metal analysis was regulated by the electrothermal atomic absorption spectroscopy using triplicate graphite tubes for various matrixes.

### **13.2 Plasma atomic emission spectrometry.**

## *13.2.1 Nitric acid and hydrogen peroxide*

Corbi *et al*. [62] mentioned the analytical method to determine the insect as heavy metal bioindicator by utilizing the plasma atomic emission spectrometry [62]. Deionized double distilled was used in this method. Aquatic insects that had been frozen were defrosted at room temperature and concerted to get 0.20 g dry weight. Insects placed in the 100 mL beaker having 5 mL nitric acid that were processed at ninety degree centigrade on hotplate until completely dried, for complete digestion I mL of hydrogen peroxide was also added. Processed samples were normalized at room temp. While filtered through filter paper in 50 mL flask. Standards run along with samples were analyzed for heavy metal detection using plasma atomic emission spectrometry.
