Multiple mosquitoes withdrawal of blood from a host can add up to a large volume. In rare cases, heavy mosquito densities have directly killed livestock as large as cattle and horses.Even more dramatically, in most of its range in North America, the main vector for the Western equine encephalitis virus is Culex tarsalis, because it is known to feed variously on mammals, birds, reptiles, and amphibians. Even fish may be attacked by some mosquito species if they expose themselves above water level, as mudskippers do.In 1969 it was reported that some species of anautogenous mosquitoes would feed on the haemolymph of caterpillars although its nutritional value is questionable. Other observations include mosquitoes feeding on cicadas and mantids. In 2014, it was shown that malaria-transmitting mosquitoes actively seek out some species of caterpillars and feed on their haemolymph, and do so to the caterpillars apparent physical detriment. Mouthparts
Mosquito mouthparts are very specialized, particularly those of the females, which in most species are adapted to piercing skin and then sucking blood. Apart from bloodsucking, the females generally also drink assorted fluids rich in dissolved sugar, such as nectar and honeydew, to obtain the energy they need. For this, their blood-sucking mouthparts are perfectly adequate. In contrast, male mosquitoes are not bloodsuckers; they only drink sugary fluids. Accordingly, their mouthparts do not require the same degree of specialization as those of females.Externally, the most obvious feeding structure of the mosquito is the proboscis.
Mechanism of action
Alters bacterial outer membrane permeability by binding to a negatively charged site in the lipopolysaccharide layer, which has an electrostatic attraction for the positively charged amino groups in the cyclic peptide portion  (this site normally is a binding site for calcium and magnesium counter ions); the result is a destabilized outer membrane
Fatty acid portion dissolves in hydrophobic region of cytoplasmic membrane and disrupts membrane integrity
Leakage of cellular molecules, inhibition of cellular respiration
Binds and inactivates endotoxin
Relative absence of selective toxicity: nonspecific for cell membranes of any type, highly toxic.Removal of the hydrophobic tail of polymyxin B yields polymyxin nonapeptide (PMBN), which still binds to LPS, but no longer kills the bacterial cell. However, it still detectably increases the permeability of the bacterial cell wall to other antibiotics, indicating that it still causes some degree of membrane disorganization. Mixture composition
Polymyxin B is composed of polymyxins B1, B1-I, B2, B3, and B6. Polymyxins B1 and B2 are considered major components. These related components are structurally identical with the exception of a variable fatty acid group on each fraction. Results from in vitro studies have shown marginal differences in MIC data when comparing the fractions. Research application
Polymyxin B is also used to induce envelope stress in order to study the organisms response to such stress. Polymyxin envelope stress assays such as this have been used for the study of small RNA (sRNA) responses in Salmonella enterica. See also
Polymyxin

References
External links
"Polymyxin B". Drug Information Portal. U.S. National Library of Medicine.