Where/How is geometry used in nature?

Image by wallygrom
A pair of Lily Beetles enjoying a warm summer evening … 🙂

From Wikipedia –
The scarlet lily beetle (Lilioceris lilii), or red / leaf lily beetle, is a leaf beetle that eats the leaves, stem, buds and flower of lilies, fritillaries and other members of the family Liliaceae. They mainly lay their eggs on Lilium and Fritillaria species. Observed in absence of Lilium and Fritillaria species, the numbers of eggs laid were significantly less and the survival rate of eggs and larvae were lowered. It is now a pest in most temperate climates where lilies are cultivated. Lily leaf beetles overwinter in the soil and come out early in spring whereas adults stay in moist environments.

Identification
Lily leaf beetles (Lilioceris lilii), belong to the Order Coleoptera, Family Chrysomelidae. In general, adult lily leaf beetles are around 6 to 9 mm (¼–⅜ in) in length. The adult’s elytra (harder forewings) are shiny and bright scarlet in colour. The lily leaf beetle’s underside, legs, eyes, antennae and head are all pitch black, greatly contrasting the bright red colour of the wings. They have large eyes, a slim thorax and a wide abdomen. Their antennae are made up of 11 segments. Furthermore, they have notched eyes and two apparent grooves on their thorax.

They are often confused with the cardinal beetles as they also have a black underside and wings that are spotless and red in colour. However, the lily leaf beetles have wings that are shinier with tiny dimples on them, they are more rounded in shape compared to the dull, narrow, flattened and elongated cardinal beetle. Another difference between the two is their food preference. Lily leaf beetles are herbivores and are usually found on lily plants eating their leaves whereas the cardinal beetles are usually found on tree bark and flowers and feed on flying insects. Lastly, the cardinal beetle has a comb-like antennae.

Lily leaf beetles are fast fliers and hide very well. Additionally, when disturbed, they make a squeaky noise to deter predators.They could also be confused with unspotted ladybirds. Lily leaf beetles however are much slimmer than ladybirds.

Distribution
The lily leaf beetle was indigenous to Europe and Asia. It has thought to been introduced to North America through the importation of bulb plants around 1945. First spotted in Montreal, it has spread throughout Canada and eastern United States within decades. It has also become an invasive alien insect in the United Kingdom, where it has established itself after its introduction in 1943. It has since spread from Surrey to as far north as Glasgow.

Life cycle
During the winter, adult lily leaf beetles rest in an undisturbed protective environment, normally shaded, cool and moist. Lily leaf beetles overwinter in soil or plant debris underneath the lily leaf plants they fed on during the previous summer and sometimes in gardens or woods quite a distance away from their host plants. In early spring, they emerge to feed on young lily leaves and mate. Females can lay up to 450 eggs each season by laying about 12 eggs on the underside of an individual lily/fritillaria leaf in irregular lines along the midrib to conceal them. Hatching of the eggs occurs in about 6 days. The larvae begin to feed underneath the leaf and working up to the rest of the plant, feeding for up to 24 days. They then burrow themselves in the ground to pupate in a cocoon formed by saliva and small particles of soil. In about 20 days, they emerge as adults and continue to feed until winter. In some cases, they are able to go through this cycle more than once in a single year.

Behaviour
Not only are the eggs laid underneath the leaf to stay hidden but they are also covered with a thick sticky brown substance for further protection. As larvae, they use their own frass to make a protective shield, allowing protection from the sun and predators. However, the fecal shield is not an adequate protection against the parasites. It actually acts as a chemical cue for the parasites to locate the larvae. As adults, a sense in danger can trigger a defense mechanism, thanatosis. The beetle becomes motionless, folds up its appendages and falls with its black under surface facing up; helping it camouflage with the ground to get away. If it is unable to escape, they are also able to ‘squeak’, by rubbing two parts of its body together, used to startle the attacker. This process is known as stridulation and could even shock a bird or any other predator that may attack the lily leaf beetle.

Human impact
Lily leaf beetles leave considerable damage on host plants. Managing the ornamental lilies have become difficult in regions where lily leaf beetles have established. Damage to the leaves and flowers can also leave the plants weakened and susceptible to diseases such as Lily grey mold.

Maritime Provinces of Canada, especially Fritillaria and Lilium gardens in Halifax, are largely affected by lily leaf beetles. A garden in Waverly, Nova Scotia has reported decline of lily species and cultivars from 50 in 1996 to only one species in 2006. A newly discovered lily species in 2007, Lilium canadense, has raised the concern for protection of this Canadian native lily and control of leaf lily beetle.

Mechanical and chemical control
There are no registered chemicals for lily leaf beetle control, and handpicking of larvae and adults prove to be most effective. However, best strategy for lily leaf beetle control is to avoid planting susceptible plants in the first place.

Although there are no specific chemicals to control lily leaf beetle, domestic insecticides registered for general leaf beetle control containing carbaryl, methoxychlor, malathion and rotenone have proven useful in controlling the populations. However, malathion and carbaryl, effective on adults and larvae, are toxic to bees and other insects, respectively. Products based on Neem extracts are useful in killing very young larvae and repelling adults without comparable harm to other insects. Neem products should be applied every 5 to 7 days after egg hatch.

Mechanical control involves mainly handpicking and crushing the larvae and eggs on the underside of foliage and removing the adults in the soil to avoid the introduction. Drowning the beetle in soapy water can be as effective as handpicking. Floating row cover has been effective in preventing the adults from feeding and laying eggs in the spring. Handpicking is deemed more effective than use of Neem-based products.

Biological control
There are no natural predators or parasites of lily leaf beetle in North America. In 1996, University of Rhode Island began testing the effectiveness of biological control of lily leaf beetle using six natural parasitoids in Europe. CAB International Bioscience Switzerland Center has also participated in this project from 1998 till 2001.

Total parasitism rate in the last instar stage averages about 90% on wild lily Lilium martagon, 75% in gardens and 60% in cultivated lily fields in Europe. Most of lily leaf beetle parasitoids are wasps that lay eggs inside the host and effectively kill all infected individuals. Parasitoid wasp, Diaparsis jucunda Holmgren (Hymenoptera: Ichneumonidae), dominates over 90% of the parasitoid infections in lily leaf beetle. However, in gardens and commercial fields, Tetrastichus setifer (Hymenoptera: Eulophidae) and Lemophagus pulcher (Szepligeti) become the dominant parasitoids in the later season.

University of Rhode Island experimented with release of European parasitoid wasp, Tetrastichus setifer, in Massachusetts from 1999 to 2001 to control for the lily leaf beetle population. The experiment had shown reduction of the beetle population. Population decline was also observed at another experiment site in Rhode Island. In 2003, another parasitoid, Lemophagus errabundus, was also released in Massachusetts and is now established in the region. Similar attempts of parasitoid release have been made in Boston with positive results.

Question by nicole l: Where/How is geometry used in nature?
All I can think of is shapes and angles, and I need to fill up one typed page. Any ideas or elaboration on the topic?

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